Exposure Adjustments, Part 7 — Photoshop Curves

This post is part of a series of posts on Adjusting Exposures. The series begins here.

When images in this post have nearly identical, top and bottom halves, top halves show effects of adjustments and bottom halves show the original image.

Curves Adjustments in Photoshop

This time I’m going to start with an actual photograph instead of a graphic image. The photo of a male Red-winged Blackbird that we adjusted with Levels in Part 2 of this series gave me the idea for this talk. The photo is displayed again in Figure 1.

Male Red-winged Blackbird

Figure 1. Unadjusted photo of a male Red-winged Blackbird.

Recall that I wanted to process the photo to bring out detail in the dark tones. When I tried doing this with Shadows/Highlights, I found myself fiddling around with Shadows/Highlights parameters more than I wanted to. Bringing out dark tones wasn’t difficult, but doing so without creating a noticeable halo was or changing the color of the sky was. It seemed like it might be easier to use Curves.

CurvesDefault

Figure 2. Adjustment menu for Curves.

Figure 2 shows the adjustment menu for Curves. The Mapping Curve (my terminology) tells how the Curves filter will map input tones on the horizontal axis to output tones on the vertical axis. Both axes have scales that run from 0 (black) to 255 (white). The straight line Default Mapping Curve in Figure 2 indicates no changes will be made: Blacks will be mapped to blacks; whites will be mapped to whites; grays will be mapped to equivalent grays. Several other standard mapping curves can be selected from the Preset menu at the top of the adjustment menu.

Other items on the adjustment menu access tools designed to help define custom Mapping Curves. There several way to do this:

  • Click the Auto button and let Photoshop find a Mapping Curve for you. Photoshop is a pretty smart program, but I think I have a better sense of how I’d like my photos to look than it does. However, sometimes the automatic mapping is a good place to start.
  • When the Edit with Points button is clicked as it is in Figure 2, click on the Mapping Curve to define a point and then drag the point to change the shape of the curve. To remove a point from the Mapping Curve simply drag it off the graph.
  • Click the Edit by Drawing button and then draw a Mapping Curve with the mouse. Clicking the Smooth Curve button will smooth the curve.
  • Move the Black and White Clipping Sliders to make Levels-like adjustments. Holding down the Option key on the Mac or Alt key on Windows while moving the Black and White Sliders displays colors that will be clipped (i.e., dark colors that can’t be made any darker because one of the Red Green or Blue values is 0 or light colors that can’t be made any lighter because one of the Red, Green or Blue values is 255).
  • Click the Target Point Adjuster button and click on a target location in the image to select a tone on the Mapping Curve. While still clicked on the image, drag up and down to change the output tone for that point.

Sometimes it’s useful to know what input and output coordinates correspond to a point of the graph. Mousing over the graph causes input and output coordinates for the mouse pointer to be displayed in the Input and Output field beneath the graph.

Like Levels, Curves can be used to adjust colors. However, as I did in the Levels discussion I’m just going to point out that in addition to having an RGB adjustment for mapping gray tones, Curves has Red, Green, and Blue scales for mapping color values. Color Mapping Curves can be defined similarly to the way the RGB Mapping Curve is defined. It’s also possible to use the Black Point, Gray Point, and White Point Samplers to select colors in the image that are to be mapped to black, 50% gray, and white.

Its mildly entertaining to see what happens to your image as you change the Mapping Curve. To start over with a fresh Mapping Curve select Default or some other mapping option from the Preset menu.

Remember that I started this discussion by saying how easy it is to make Curves adjustments. All those options don’t make it sound easy at all. Here’s all I had to do to adjust the Red-winged Blackbird photo:

  1. I clicked the Target Point Adjuster button and then clicked on the sky. This put a point corresponding to the sky’s gray tone on the Mapping Curve.
  2. With the Target Point Adjuster button still depressed, I then clicked on a gray spot on the Blackbird’s breast and dragged the mouse up and down until I liked the effect.

That’s it. The adjusted Red-winged Blackbird photo is in Figure 3. The Curves adjustments are shown on Figure 4.

Male Red-winged Blackbird

Figure 3. Red-winged Blackbird photo from Figure 1 after it has been adjusted with Curves.

Red-wingedBlackbirdCurvesAdjustments

Figure 4. Curves adjustment for the Red-winged Blackbird photo in Figure 3. Two points were added to the Mapping Curve. The point in the lower left is the gray tone value for a gray spot on the bird’s breast. The point at the upper right is a gray tone value for the sky.

Notice that I achieved more detail in dark tones by making the Mapping Curve steeper. Dark grays were then mapped to lighter grays. This is an example of a general rule: Make mapping Curves steeper in tonal regions where you want to bring out more detail.

Let’s try this with the contrived spider graphic used to demonstrate Shadows/Highlights adjustments. The result is shown in Figure 5.

PaperSpidersCurves

Figure 5. The top half of the image show the results of adjusting the spider graphic with the Curves adjustments shown in Figure 6. The bottom half of the image is unadjusted.

The Mapping Curve for the Curves adjustment is displayed in Figure 6. The middle point assures that the background tone will not be changed. The two points adjacent to it are needed to assure that values of output tones will increase when values of input tones increase.

PaperSpidersCurvesAdjustment

Figure 6. Curves adjustments for the spider graphic in Figure 5.

Curves vs. Levels

Black and White Input Sliders in Curves act just like Black and White Input Sliders in Levels. Once the Black and White input range has been established with the Black and White Input Sliders, ends of black end of the curve can be moved up and the while end of the curve can be moved down to simulate the effect of the Black and White Output Sliders in Levels.

The Gray Slider is the only Levels adjustment that’s missing in Curves. In effect, the Gray Slider adjusts the shape of a curve by setting one parameter. Curves allows you to specify the shape of the curve by placing points on it. In effect, you can set as many parameters as you care to. The additional flexibility of Curves comes at a price. It’s easy to get trapped into spending lots of time adding points and moving them around while trying to achieve a perfect adjustment.

Without falling into the trap of perfectionism, I’m going to conclude this post with the application of Curves to the Jackrabbit photo that I adjusted with Levels. Figures 7 and 8 show that photo and the final Levels adjustment:

Jackrabbit_20130630_5754_Original

Figure 7. Unadjusted photograph of a jackrabbit.

Jackrabbit_20130630_5754_b10w205g095ob15ow240

Figure 8. Jackrabbit photo with Black, White and Gray Input Levels Sliders set to 10, 205, and 0.95 and Black and White Output Levels Sliders set to 15 and 240.

Figure 9 shows the jackrabbit photo with a Curves adjustment intended to mimic the Levels adjustments for the photo Figure 8.

Jackrabbit_20130630_5754_Curves

Figure 9. Jackrabbit photo after the Curves adjustments shown in Figure 10.

Figure 10 displays the Curves adjustments used to generate Figure 9. The short horizontal line on the lower left portion of the Mapping Curve causes all tones between 0 and 10 to be mapped to 15. The longer horizontal line at the upper right portion of the mapping curve causes all tones between 205 and 255 to be mapped to 240. The point in the middle of the Mapping Curve was selected to adjust the mapping of tones between 10 and 205.

JackrabbitCurvesAdjustment

Figure 10. Curves adjustments intended to mimic the Levels adjustments for the Jackrabbit photo in Figure 9.

I once thought that Curves adjustments could mimic Levels adjustments exactly. That’s not the case. To see why consider the Histograms in Figures 11 and 12.

JackrabbitHistogramb10w205g095ob15ow240

Figure 11. Histogram for the Levels-adjusted Jackrabbit photo in Figure 8.

JackrabbitCurvesHistogram

Figure 12. Histogram for the Curves-adjusted Jackrabbit photo in Figure 9.

There’s clearly something peculiar about the Levels algorithm. Combing occurs when a smaller range of values is mapped to a larger range of values. Spiking occurs when a larger range of values is mapped to a smaller range of values. In this case, the Levels Histogram exhibits both combing and spiking. I image this happens because Levels calculations are done in stages with rounding to integer values at the end of each stage. There’s no way to simulate that kind of effect with the a smooth Curves calculation that only does rounding at the end.

The Curves Histogram is much as you’d expect it to be. The steeper slope of the Mapping Curve for lighter tones causes the combing. For darker tones the Mapping Curve closely matches the Default Mapping Curve. Because they distort the Histogram less, Curves adjustments are preferable to Levels adjustments for situations that call for changes to both the input and the output range combined with gamma adjustments made by moving the Levels Gray Slider.

Exposure Adjustments, Part 6 — Photoshop Shadows/Highlights

This post is part of a series of posts on Adjusting Exposures. The series begins here.

When images in this post have nearly identical top and bottom halves, top halves show effects of adjustments and bottom halves show the original image.

Shadows/Highlights Adjustments in Photoshop

When we look at a scene, we can see details in both bright and dark areas that photographers can’t pick up in a single image. If the exposure is set to pick up details in bright areas, details are lost in dark areas. If the exposure is set to pick up details in dark areas, details are lost in bright areas. Scenic photographers can deal with this problem by taking several photos with different shutter speeds and combining them with software for creating high dynamic range (HDR) images.

Wildlife photographers rarely have the luxury of taking multiple photographs of the same image. They have to find other ways to bring out details in both bright and dark areas of their photos. One approach is to mask adjustments that bring out details in shadows so they apply only to dark areas of a photo and mask adjustments that bring out details in highlights so they apply to only dark areas of a photo.

Manual creation of masks can be difficult and tedious. The Shadows/Highlights adjustment attempts to simplify the process by combining automatic mask creation with exposure adjustments. It’s accessed though the command Photoshop command menu at Image / Adjustments / Shadow/Highlight… Figure 1 shows the adjustment menu.

ShadowsHighlightsAdjustments

Figure 1. The Shadows/Highlights adjustment menu.

These following adjustments are possible:

  • Amount determines the amount of the adjustment. For shadows it’s the amount of lightening. For highlights it’s the amount of darkening. (Photoshop CC defaults: Shadows Amount: 35%; Highlights Amount: 0%).
  • Tonal Width specifies the range of tones affected by the adjustment. A low tonal width for shadows means that only the darker areas of the image will be affected. A low tonal width for highlights means that only the lighter areas of the image will be affected. As tonal width is increased more mid-tone regions are affected. (Photoshop CC defaults: 50%).
  • Radius controls the size of the area used to determine whether a pixel is in a shadow or a highlight. If the shadows amount is non-zero, all pixels in a shadow area are lightened. If the highlights amount is non-zero, all pixels in a highlight area are darkened. The optimum radius depends on the nature of shadow and highlight areas and the size of the image. Increasing Radius softens the edges of affected areas. Decreasing Radius sharpens them.  (Photoshop CC defaults: 30 px).
  • Color Correction changes the saturation of colors modified by Shadows/Highlights. Brightening dark pixels or darkening bright pixels may introduce “hidden” colors. (Photoshop CC default: +20).
  • Midtone Contrast adjusts the contrast of mid-tones. (Photoshop CC defaults: 0).
  • Black Clip and White Clip set absolute black or absolute white for a Levels adjustment that Shadows/Highlights makes prior to making other adjustments. These values set the amount of clipping you are willing to tolerate for that adjustment. Setting both values to 0 turns off the Shadows/Highlights Levels adjustment. (Photoshop CC defaults: 0.01% for both).

Notice that Show More Options is checked. If it is unchecked, only the Amount sliders are displayed.

Tip: I always convert layers to Smart Objects with a Layer / Smart Objects / Convert to Smart Object command before manipulating them with Shadows/Highlights adjustment. This allows me to go back to examine or modify the Shadows/Highlights settings later. If I leave the layer as a Smart Object and save the file as a Photoshop document, the recoverable and modifiable Shadows/Highlights settings get saved with the file.

Let’s see what Shadows/Highlights does with at the high-contrast contrived spider graphic that I used to demonstrate some of the deficiencies of the Levels adjustment. The image is displayed again in Figure 2.

PaperSpiders

Figure 2. A contrived spider graphic with subtle detail in both dark and light areas.

The effect of setting Shadows and Highlights Amounts to 100% and leaving other settings at Photoshop CC defaults produces the image in Figure 3. (Setting Shadows/Highlights Amounts to 100% is rarely appropriate for photographs. I’ve used these settings here to maximize some of the effects.)

PaperSpidersSHa100-100

Figure 3. The top half of the image shows the effect of modifying the spider graphic in Figure 2 with Shadows/Highlights. Shadows and Highlights Amounts are set to 100%. Other settings are left at Photoshop CC defaults. The bottom half of the image is unadjusted.

To a limited extent the adjustment worked: Shadows/Highlights enhanced detail in both dark and light areas of the image in Figure 3. However, there are problems with the background. The dark spider is surrounded by a halo. The light spider is surrounded by a shadow.

Halos around shadows and shadows around highlights are difficult to avoid completely when images are adjusted by Shadows/Highlights, but they can be minimized by reducing Amounts or Tonal Widths and modifying Radius adjustments. The best values for these parameters depend on the image being treated and personal taste. Generally, Amounts and Tonal Widths should be set to minimize unwanted effects on mid-tones. Some authors suggest that a good rule of thumb is to set the Radius to the size of the shadow and highlight areas that you are trying to emphasize. A better rule may be to apply Radius settings to values that depend on the sharpness of transitions between mid-tone areas and shadows or highlights. A small radius works well for for sharp transitions. A larger radius is better for more gradual transitions.

Transitions between mid-tones and shadows or highlights in my contrived example are about as sharp as you’ll ever come across. I found that when I left Amounts at 100%, Radius settings of 0 worked well. When Radius settings were 0, I was able to leave Tonal Widths at fairly high values: 50% for the Shadows Tonal Width and 41% for the Highlights Tonal Width. The result of these adjustments is shown in Figure 4.

PaperSpidersSHa100-100tw50-41r0-0

Figure 4. Effect of modifying the spider graphic in Figure 2 with Shadows/Highlights. Shadows and Highlights Amounts are 100%, Shadows Tonal Width is 50%. Highlights Tonal Width is 41%. Radii are 0 px, which seems appropriate for the extremely sharp transitions between shadows, highlights and mid-tones.

Let’s look at an example in which transitions between shadows an highlights are more gradual. I altered the spider graphic to demonstrate the effects of Shadows/Highlights when the edges of shadows and highlights are less well defined. The altered graphic is shown in Figure 5.

BlurredPaperSpiders

Figure 5. An altered spider graphic in which edges of shadows and highlights are less well defined.

One might expect that the Shadows/Highlights adjustments that created Figure 4 from original spider graphic in Figure 2 would also work well for enhancing the shadows and highlights in the altered spider graphic in Figure 5. The result of applying these adjustments to Figure 5 is shown in Figure 6.

BlurredPaperSpidersSH100-100tw50-41r0-0

Figure 6. Effect of modifying the altered spider graphic in Figure 5 with Shadows/Highlights. Shadows and Highlights Amounts are 100%, Shadows Tonal Width is 50%. Highlights Tonal Width is 41%. Radii are 0 px.

The adjusted image is both dramatic and interesting, but probably not representative of the kind of enhancement one usually seeks for photgraphs. Two things cause the bizarre effects: Background mid-tone pixels get dragged into adjustments because Tonal Widths are too high, and zero values for Radii make transitions from background mid-tones to shadows and highlights too abrupt.

Figure 7 a Shadows/Highlights adjustment to the altered spider graphic in Figure 6 with parameters set to more appropriate values.

BlurredPaperSpidersSHa100-100tw25-15r11-11mc+18

Figure 7. Effect of modifying the altered spider graphic in Figure 5 with Shadows/Highlights with parameters set to values more appropriate to the image. Shadows and Highlights Amounts are 100%, Shadows Tonal Width is 25%. Highlights Tonal Width is 15%. Radii are 11 px. Residual effects on the background were reduced by setting Midtone Contrast to +18.

The result shown in Figure 7 is not perfect. A bit of haloing and shadowing is evident in sharp corners. Decreasing Radius values would reduce these effects at the expense of loss of more detail in shadows and highlights.

 Shadows/Highlights Adjustments to a Photograph

Figure 8 is a photograph of Milkweed Longhorn Beetles that was taken with a macro lens and ring-light flash. The background, which is further from the flash, is dark and poorly lighted. The milkweed seed pod and particularly the stem leading to it are perhaps too brightly lighted.

Milkweed Longhorn Beetles

Figure 8. Unadjusted photograph of Milkweed Longhorn Beetles.

Figure 9 shows a version of the Milkweed Longhorn Beetles photograph adjusted by Shadows/Highlights settings of Shadows Amount: 10%; Shadows Tonal Width: 50%; Shadows Radius: 13px; Highlights Amount: 20%; Highlights Tonal Width 50%; and Highlights Radius: 7px.

Milkweed Longhorn Beetles

Figure 9. The Milkweed Longhorn Beetle photograph from Figure 8 after Shadows/Highlights adjustments.

Tip: Shadows/Highlights adjustments create histogram combing effects similar to those created by Levels adjustments. These effects can be minimized by loading raw files as 16-bit images instead of 8-bit images. See my post of Levels adjustments for more detail.

Tip: Appropriate values for Radius parameters scale with image size: Large Radii for larger images; smaller Radii for smaller ones. Subtle changes is results make selecting appropriate values for Radius parameters tricky. One way to deal with this problem is to set Amount to 100% while selecting the corresponding Radius and then reduce Amount to a more reasonable value once that Radius has been established.

Figure 10 is a photograph of an American Beaver that was taken with a long lens late in the afternoon. Sun shining on the wake created as the beaver was swimming to the east creates some distracting glare that can be toned down with Shadows/Highlights.

American Beaver

Figure 10. Unadjusted photograph of an American Beaver.

Figure 11 shows a version of the American Beaver photograph adjusted by Shadows/Highlights setting of Shadows Amount: 15%; Shadows Tonal Range: 50%; Shadows Radius: 20px; Highlights Amount:: 30%; Highlights Tonal Range: 50%; and Highlights Radius: 7px.

American Beaver

Figure 11. American Beaver photograph from Figure 10 after adjustment with Shadows/Highlights.

It’s worth stating again that Shadows/Highlights adjustments to a pixel’s tone depend on where that pixel is located. The pixel will be treated differently if it’s surrounded by dark pixels than if it’s surrounded by light pixels. In the absence of masking, all other adjustments to a pixel’s tone depend only on what that tone is. In the next post return to talking about Curves — an adjustment that allows a great deal of flexibility in determining how various tones get adjusted.

Adjusting Exposures, Part 5 — Photoshop Levels

This post is part of a series of posts on Adjusting Exposures. The series begins here.

When images in this post have nearly identical top and bottom halves, top halves show effects of adjustments and bottom halves show the original image.

Levels Adjustments in Photoshop

Figure 1 shows the Histogram window and the Levels adjustment menu.

LevelsDefault

Figure 1. Histogram and Levels adjustments. Data are for the image in Figure 2.

The Levels adjustment modifies an image by mapping input tones to output tones. Three parameters specify the range of input tones:

  • Black Slider — the lightest tone in the original image that will be mapped to the darkest tone on the output range.
  • White Slider — the darkest tone in the original image that will be mapped to the lightest tones in the output range.
  • Gray Slider — defines the tone in the original image that will be mapped to the middle tone in the output range.

The Black Slider and White Slider have values from 0 (black) to 255 (white). The Gray Slider has values of Gamma for a transformation that maps the tones between tones Black and White Sliders onto the output range. Gamma has a value of 1.0 when the Gray Slider is halfway between the Black Slider and the White Slider. The value of Gamma is greater than 1.0 if the Gray Slider is closer to the Black Slider and less than 1.0 if the Gray Slider is closer to the White Slider.

The output range is specified by an Output Black Slider and an Output White Slider. Tones darker than the Black Slider value are mapped to the darkest tone in the output range. Tones between the Black Slider value and the tone defined by the Gray Slider are mapped to tones between the darkest tone and the middle tone in the output range. Tones between the tone defined by the Gray Slider and the White Slider value are mapped to tones between the middle tone and the lightest tone in the output range. Tones lighter than the White Slider value are mapped to the lightest tone in the output range.

I’m not going to talk about color adjustments other than to point out that in addition to having an RGB adjustment for mapping gray tones, Levels has Red, Green, and Blue scales for mapping color values. Color mappings can be set with slider controls similar to the Black, Gray, White, and Output Levels Sliders used for RGB adjustments. It’s also possible to use the Black Point, Gray Point, and White Point Samplers to select colors in the image that are to be mapped to black, 50% gray, and white.

Tip: Holding down the Option key on the Mac or Alt key on Windows while moving the Black and White Sliders displays colors that will be clipped (i.e., dark colors that can’t be made any darker because one of the Red Green or Blue values is 0 or light colors that can’t be made any lighter because one of the Red, Green or Blue values is 255).

To see how the Levels adjustment works, let’s look at a low contrast image. The graphic in Figure 2 was constructed by using a soft brush to paint various tones on a gray background. You can click on this image to get a larger version that can be downloaded for trying out some of these adjustments yourself. The histogram and default Levels adjustments for the image in Figure 2 are shown in Figure 1.

Percents

Figure 2. Example of an image with and abundance of mid-tones, but few light and dark tones.

Let’s see how levels might be used to add a little pop to the image in Figure 2 by spreading colors out over a larger range of tones. For the image in Figure 2, the Black Slider can be increased to 98 and the White Slider can be decreased to 195 without clipping any of the grays. The resulting image is shown in Figure 3. Some colors were clipped by the adjustment, but grays were not.

PercentsLevels98_195

Figure 3. Image with Black, Gray and White Levels Sliders set to 98, 1.00, and 195. Output Black and White sliders are set to 0 and 255 respectively. As with other examples, the bottom section of the image shows an unadjusted version of the image.

Levels98_195

Figure 4. Histogram and Levels adjustments for the image in Figure 3. (Colors in the unadjusted bottom section of the image are not included in the Histogram.)

Figure 4 shows the Histogram and Levels settings for the adjusted image in Figure 3. The Histogram display in the upper panel shows the histogram after adjustment. Notice the comb effect. This comes about because the limited number of tones from 98 to 255 are spread out over the output range of 0 to 255. The Levels display in the lower panel shows the histogram before the adjustment. Clipped tones, which in this case correspond to some of the colored dashes, fall outside the range between the Black Slider and the White Slider.

The background in the adjusted image shown in Figure 3 is now much darker than the background in the original. You can see why this might be by looking at the position of the Gray Slider in the Levels adjustment. It’s significantly to the right of the peak tone in the Levels Histogram. This peak corresponds to the gray background color that dominates in the original image.

The Gray Slider can be moved to make the background color in the adjusted image identical to the background color in the original. With Output Levels of 0 to 255, tones between the Black Slider value and the tone indicated by the Gray Slider will be spread between Black and 50% gray. If we want the background color to be unchanged we’ll have to move the Gray Slider to the left so it’s closer to the gray peak in the original image. The result of doing this is shown in Figure 5.

PercentsBlack98Gray17White195

Figure 5. Adjusted images with Black and White Sliders set to 98 and 195 and the Gray Slider set to 1.7.

Recall that Gray Slider values are Gamma parameters for a transformation rather than tone values. In this case background grays are matched reasonably well by setting the Gray Slider to a Gamma value of 1.7. Figure 6 shows the histogram for the image in Figure 5. Note that the peak is now at the center of the gray scale.

LevelsBlack98Gray17White195

Figure 6. Histogram for the image in Figure 5. (Colors in the unadjusted bottom section of the image are not included in the Histogram.)

Levels Adjustments to a Photograph

Let’s try adjusting Levels on the Jackrabbit photograph discussed in the post on Basic Adjustments with Camera Raw 8 and displayed again in Figure 7.

Jackrabbit_20130630_5754_Original

Figure 7. Unadjusted photograph of a jackrabbit.

Jackrabbit_UnadjustedLevels

Figure 8. Histogram and Default Levels adjustments for the jackrabbit photo in Figure 7.

Although my normal workflow is use Photoshop to refine Basic Adjustments I’ve made in Camera Raw, for purposes of demonstrating Levels I’ll start with the original unadjusted image in Photoshop for this example. The Histogram and Levels adjustments for the unadjusted jackrabbit photo are shown in Figure 8.

As we noted earlier, the histogram for the unadjusted jackrabbit photo is shifted toward black. Occurrences of tones also fall off dramatically for both a both ends of the scale. At the cost of only a bit of clipping in the blacks, these deficiencies in the image can be remedied by moving the Black Slider to the right and the White Slider to the left. I chose Black and White Slider values of 10 and 205 for my adjustment.

The Black and White Slider adjustments left the Gray Slider on the left site of the tone peak. To my eye the resulting image was too bright. Moving the Gray Slider right to a Gamma value of 0.95 cut down on the overall brightness and enhanced the detail in the jackrabbit’s coat. The results of these adjustments and the associated Histogram are shown in Figures 9 and 10.

Jackrabbit_20130630_5754_b10w205g095

Figure 9. Jackrabbit photo with Black, White and Gray Levels Sliders set to 10, 205, and 0.95.

JackrabbitHistogramb10w205g095

Figure 10. Histogram for the jackrabbit photo in Figure 9. Note the combing associated with the Levels adjustments. A small amount of black clipping is apparent from small spike on the left side of the histogram.

One final levels adjustment of this jackrabbit photo may be called for. There really weren’t any dark shadows or bright highlights in the scene that the photo is attempting to depict. Perhaps an adjustment of Output Levels is would be in order. Figure 11 shows the result of setting the Output Black Slider to 15 and the Output White Slider to 240. To my eye this is a more accurate rendition of the scene than the image in Figure 9.

Jackrabbit_20130630_5754_b10w205g095ob15ow240

Figure 11. Jackrabbit photo with Black, White and Gray Input Levels Sliders set to 10, 205, and 0.95 and Black and White Output Levels Sliders set to 15 and 240.

JackrabbitHistogramb10w205g095ob15ow240

Figure 12. Histogram for the jackrabbit photo in Figure 11.

Figure 12 shows the Histogram for the photo in Figure 11. Adjusting Output Levels completely eliminated dark shadows and bright highlights and produced some additional combing in the Histogram.

Combing and Bit Depth

JPEG files and most display devices have a bit depth of 8 bits per channel: 28 or 256 values of Red; 28 values of Green; and 28 values of Blue for 224 (16,777,216) possible colors and 256 possible gray tones. Levels adjustments almost always eliminate some colors and gray tones from images. Raw files created by modern digital cameras have bit depths ranging from 12 to 16 bits per channel: between 236 (68,719,476,736) and 248 (281,474,976,710,656) possible colors and 212 (4,096) to 216 (65,536) possible gray tones.

Consider the adjustment of Input Levels in the jackrabbit example. Setting the Black Slider to 10 eliminated 10 dark gray tones and setting the White Slider to 205 eliminated 50 light gray tones. That left 196 gray tones to be mapped to the range of 0 to 255. No gray tones are available to map to 60 gray tones — approximately 23% of the output range is eliminated.

Photoshop can process images that have 8, 16 and 32 bits per channel. To this point, all of my examples have been created with 8-bit images. Suppose that instead of processing an 8-bit per channel image we had processed a 16 bit per channel image derived from a raw file containing a 12-bit image with 4,096 possible gray tones. The same proportion of gray tones would be eliminated by the adjustments — in this case 960 values. However, 3,616 values would remain. Most of the combing is eliminated when these 3,136 gray tones are mapped to the 256 gray tones used for displays.

Figure 13 shows a jackrabbit image that was derived from a 14-bit raw file that was processed as a 16-bit image and modified with the same Levels adjustments as the image in Figure 11. The difference between the two images is subtle. However, when I compare the the larger versions of the images that I get by clicking on Figures 11 and 13, it seems to me that the image from Figure 13 shows finer detail than the image from Figure 11. To me this is particularly apparent in variations of color in the jackrabbit’s fur.

Figure 14 shows the Histogram the image in Figure 13. Levels adjustments created the slightly jagged edges, but the severe combing has been eliminated.

Jackrabbit_20130630_5754_b10w205g095ob15ow240-16bit

Figure 13. Jackrabbit photo derived from a raw file opened as a 16-bit image and modified with Black, White and Gray Input Levels Sliders set to 10, 205, and 0.95 and Black and White Output Levels Sliders set to 15 and 240.

 JackrabbitHistogramb10w205g095ob15ow240-16bit

Figure 14. Histogram for the jackrabbit photo in Figure 13.

I generally have my version of Camera Raw set to open files in 16-bit mode instead of 8-bit mode. As it comes out of the box (or off the web as the case may be), Camera Raw sends images to Photoshop in 8-bit mode. To switch to 16-bit mode, locate the lineat the bottom of the Camera Raw display that looks something like the one shown in Figure 15, click on it, and set Depth to 16 bits/channel in the menu that gets displayed. The new setting with persist until you change it.

CameraRawSettings

Figure 15. To charge the mode with which Photoshop images get opened from Camera Raw, click on the line like this at the bottom of the Camera Raw display.

Saving JPEG versions of files automatically converts them to 8-bit more. Some other formats like TIFF can be either 8-bit or 16-bit mode. The Photoshop  Image / Mode command can be used to convert a 16-bit image to an 8-bit image for applications like printing that often require 8-bit images.

(A note about histograms: Histograms in these posts were collected from Photoshop versions of files before they were saved as JPEGs. Converting files to JPEG format destroys some information and tends to smooth out histograms a bit. You’ll get slightly different histograms if you download example JPEG files and load them into Photoshop.)

Levels Can’t Improve Some Images

Generally, Black and White Slider adjustments in Levels work only for images that have few dark or light tones. Unless used judiciously, Black Slider adjustments can destroy details in shadows and White Slider adjustments can destroy details in highlights. I contrived the image in Figure 16 to demonstrate this.

PaperSpiders

Figure 16. Both dark and light spiders in this image have detail that could be enhanced with Levels adjustments, but without using multiple masked Levels adjustments, it’s not possible to show detail in both highlights and shadows.

Figure 17 shows the Histogram for the image in Figure 16. It has sharply peaked distributions in both dark shadows and bright highlights and a very sharp peak for the gray background.

PaperSpidersHistogram

Figure 17. Histogram associated with the image in Figure 16.

We’d like to enhance the detail in both shadows and highlights without affecting the gray background. Black, White and Gray Slider adjustments can be set to enhance either shadows or highlights after which Output Levels can be adjusted to return the background to gray. Several examples of these adjustments are displayed in Figures 18 through 21. As with other examples of this sort, the bottom half of the display shows the unadjusted image.

PaperSpidersBlack225

Figure 18. Black Slider at 225; Output Levels adjusted to match background.

PaperSpidersWhite30

Figure 19. White Slider at 30; Output Levels adjusted to match background.

 

 

PaperSpidersGray0p18

Figure 20. Gray Slider at 0.18 (which moved it to the left side of the highlights); Output Levels adjusted to match background.

PaperSpidersGray3p10

Figure 21. Gray Slider at 3.10 (which moved it to the right side of the shadows peak); Output Levels adjusted to match background.

 

 

 

 

 

 

 

 

Levels Adjustment to Another Photograph

I don’t want to leave you with the impression that Levels adjustments are only useful for images like the jackrabbit that have bell-shaped histograms with few dark shadows and few bright highlights. Consider the photograph of a Red-winged Blackbird in Figure 22.

Male Red-winged Blackbird

Figure 22. Unadjusted photo of a male Red-winged Blackbird.

Figure 23 displays the histogram for the unadjusted Red-winged Blackbird photo. Clearly it would be impossible to adjust either the White or the Black Slider without clipping some highlights of shadows. In fact, the narrow peak on the right side of the histogram indicates that some highlights may already have been clipped.

Red-wingedBlackbirdOriginalHistogram

Figure 23. Histogram associated with the Red-winged Blackbird photo in Figure 20.

Clipped highlights isn’t the only problem with the Red-winded Blackbird photo. The main subject is dark and detail is lost in dark areas of the photograph. Some of this detail can be recovered by moving the Gray Slider toward black on the left side of the histogram. This enhances contrast in the darker tones by spreading them out over a larger tone range.

Recall that, contrary to what one might expect, the Gray Slider has a value of 1.0 when it’s set to 50% gray. Moving it to the left increases its value. Moving it to the right decreases its value. Figure 24 shows what happens when the Gray Slider is set to 1.15.

Male Red-winged Blackbird

Figure 24. Red-winged Blackbird photo after a Levels adjustment moving the Gray Slider to the left so it has a value of 1.15.

Figure 25 is the histogram for the photo in Figure 24. Notice the combing created by spreading the limited number of dark tones over a wider range and the additional small peaks created by squeezing lighter tones into a narrower range. I used an 8-bit image for this example. If I had used a 16-bit image, changes in the histogram would have been much less apparent.

Red-wingedBlackbird1p15Histogram

Figure 25. Histogram for adjusted Red-winged Blackbird photo shown in Figure 24.

As we’ve seen, the Levels adjustment offers a powerful tool for enhancing many images, but it falls short for images that have important detail in both shadows and highlights. In my next post I’ll discuss the Shadows/Highlights adjustment. It’s designed to define shadows and and highlights in an image and handle them separately.

Adjusting Exposures, Part 4 — Basic Photoshop Adjustments

This post is part of a series of posts on Adjusting Exposures. The series begins here.

Frankly, I prefer the basic exposure adjustments in Camera Raw 8 to those in Photoshop. This post is included in the series for completeness. I only use basic exposure adjustments in Photoshop when they are combined with a mask that limits their effects to selected regions on my photograph.

Except as noted, the top halves of the black-to-white gradient images in this post show effects of adjustments. The bottom halves show the original image. If you’d like try out adjustments yourself, you’ll find the black-to-white gradient image here.

The Exposure Adjustment in Photoshop

Figure 1 shows the effect of setting Exposure to +1 with a Photoshop adjustment layer. The effect on lighter grays is similar to setting Exposure to +1 in Camera Raw. The pure black on the left side of the image is maintained even if the exposure is increased the maximum amount.

GadientDemoPsExposure+1

Figure 1. Black-to-white gradient image with Exposure set to +1 with a Photoshop Exposure adjustment layer.

Figure 2 shows the effect of setting Exposure to -1 in Photoshop.

GadientDemoBrExposure-1

Figure 2. Black-to-white gradient image with Exposure set to -1 with a Photoshop Exposure adjustment layer.

Exposure adjustments in Photoshop and Camera Raw 8 are qualitatively similar. For example, whites are turned to gray as exposure is decreased. However, they aren’t identical. Figures 3 and 4 compare the effects of increasing and decreasing Exposure in the two programs.

CompareGadientDemosPsExposure+1BrExposure+1

Figure 3. Comparison of exposure adjustments in Photoshop CC with Camera Raw 8. Both Exposures are set to +1.

CompareGadientDemosPsExposure-1BrExposure-1

Figure 4. Comparison of exposure adjustments in Photoshop CC with Camera Raw 8. Both Exposures are set to -1.

I frequently use a masked Photoshop Exposure layer to decrease the brightness of areas of my photos that are likely to distract the viewer from the main subject.

In addition to the Exposure slider, the Photoshop Exposure adjustment has an Offset slider, a Gamma Correction slider, and eyedropper samplers for black, gray and white. Because similar effects can be obtained more intuitively with other adjustments, I rarely use these controls in Photoshop exposure adjustments. I will not discuss them here.

The Brightness and Contrast Adjustments in Photoshop

When computer software doesn’t work exactly as expected users refer to the unexpected effect as a “bug.” Software developers may refer to the same effect as a “feature.” For several releases of Photoshop the Brightness and Contrast adjustment was such a bug/feature. Recall that the Brightness and Contrast in Camera Raw modifies mid-tones but leaves blacks and whites unchanged. As you can see in Figures 5 through 8, the Brightness and Contrast adjustments in Photoshop now affect only mid-tones.

GadientDemoPsBrightness+50

Figure 5. Black-to-white gradient with Brightness set to +50 in Photoshop.

GadientDemoPsBrightness-50

Figure 6. Black-to-white gradient with Brightness set to -50 in Photoshop.

GadientDemoPsContrast+25

Figure 7. Black-to-white gradient with Contrast set to +25 in Photoshop.

GadientDemoPsContrast-25

Figure 8. Black-to-white gradient with Contrast set to -25 in Photoshop.

In earlier versions of the Photoshop Brightness and Contrast adjustments affected blacks and whites as well as mid-tones. Depending on one’s point of view, this was either a bug or a feature. Adobe has fixed the “bug,” but left the “feature” by allowing users select a Use Legacy option on the Brightness and Contrast adjustment menu. Figures 9 through 12 demonstrate the effects of legacy brightness and contrast adjustments.

GadientDemoPsLegacyBrightness+50

Figure 9. Black-to-white gradient with Legacy Brightness set to +50 in Photoshop.

GadientDemoPsLegacyBrightness-50

Figure 10. Black-to-white gradient with Legacy Brightness set to -50 in Photoshop.

GadientDemoPsLegacyContrast+25

Figure 11. Black-to-white gradient with Legacy Contrast set to +25 in Photoshop.

GadientDemoPsLegacyContrast-25

Figure 12. Black-to-white gradient with Legacy Contrast set to -25 in Photoshop.

Although the legacy Brightness and Contrast adjustment doesn’t do what users may expect, it could be used in conjunction with masks to de-emphasize distracting areas of an image by making them darker or less contrasty.

In my next post I’ll talk about Levels adjustments — one of several more “advanced” tools that Photoshop offers for manipulating exposures.

 

Adjusting Exposures, Part 3 — Basic Adjustments in Camera Raw 8

This post describes basic exposure adjustments available in Camera Raw 8. It is part of a series of posts on Adjusting Exposures that begins here.

Adjustments in legacy (i.e., old) versions of Camera Raw are described in Part 2 of the series. The adjustment menu in legacy versions of Camera Raw is different (and to my way of thinking less intuitive). You may run into the legacy adjustment menu even if you are using the latest version of Camera Raw.  Newer versions of Camera Raw recognize legacy adjustments that have been saved and switch to legacy adjustment menus when legacy adjustments are encountered.

Except as noted, the top halves of the black-to-white gradient images in this post show effects of adjustments. The bottom halves show the original image. If you’d like try out adjustments yourself, you’ll find the black-to-white gradient image here.

Camera Raw Exposure Adjustments

Figure 1 shows the effect of setting Exposure to +1 in Camera Raw 8. Grays become lighter, but pure black on the left side is preserved. Figure 2 shows the effect of setting Exposure of the black-to-white gradient to -1 in Camera Raw 8. Everything that isn’t already black becomes darker. Pure white on the right side of the image is not preserved.

GadientDemoNewBrExposure+1

Figure 1. Black-to-white gradient image with Exposure set to +1 in Camera Raw 8.

GadientDemoNewBrExposure-1

Figure 2. Black-to-white gradient image with Exposure set to -1 in Camera Raw 8.

Exposure adjustments in Camera Raw 8 are consistent with what photographers would expect from camera adjustments. Whites are rendered as grays in photographs that are underexposed because of camera settings.

Camera Raw Contrast Adjustments

Figures 3 and 4 demonstrate the effect of Contrast adjustments in Camera Raw 8. As with legacy versions of Camera Raw, increasing Contrast makes dark grays darker and light grays lighter. Decreasing Contrast makes dark grays lighter and lighter grays darker. In both cases, whites and blacks are preserved.

GadientDemoNewBrContrast+25

Figure 3. Black-to-white gradient image with Contrast set to +25 in Camera Raw 8.

GadientDemoNewBrContrast-25

Figure 4. Black-to-white gradient image with Contrast set to -25 in Camera Raw 8.

There is very little difference between Contrast adjustments Camera Raw 8 and those in legacy versions.

Camera Raw Highlights and Shadows Adjustments

Figures 5 and 6 demonstrate the effect of Highlights adjustments in Camera Raw 8. Notice that darker grays are affected little by these changes.

GadientDemoNewBrHighlights+25

Figure 5. Black-to-white gradient image with Highlights set to +25 in Camera Raw 8.

GadientDemoNewBrHighlights-25

Figure 6. Black-to-white gradient image with Highlights set to -25 in Camera Raw 8.

Adjustments to Shadows have the opposite effect: Darker grays are affected more than lighter ones. Figures 7 and 8 show examples of these adjustments.

GadientDemoNewBrBlacks+25

Figure 7. Black-to-white gradient image with Shadows set to +25 in Camera Raw 8.

GadientDemoNewBrShadows-25

Figure 8. Black-to-white gradient image with Shadows set to -25 in Camera Raw 8.

Camera Raw Whites and Blacks Adjustments

Figures 9 and 10 demonstrate the effects of Whites adjustments in Camera Raw 8. As with Highlights adjustments, darker grays are affected little by Whites adjustments.

GadientDemoNewBrWhites+25

Figure 9. Black-to-white gradient image with Whites set to +25 in Camera Raw 8.

GadientDemoNewBrWhites-25

Figure 10. Black-to-white gradient image with Whites set to -25 in Camera Raw 8.

The effects of adjusting Blacks with Camera Raw 8 are shown in Figures 11 and 12. It’s no surprise that light grays are little affected by these adjustments.

GadientDemoNewBrBlacks+25

Figure 11. Black-to-white gradient image with Blacks set to +25 in Camera Raw 8.

GadientDemoNewBrBlacks-25

Figure 12. Black-to-white gradient image with Blacks set to -25 in Camera Raw 8.

Comparison of Highlights/Whites and Shadows/Blacks Adjustments

It’s challenging to see the difference between adjusting Highlights and adjusting Whites in the previous examples. The differences are clarified by Figures 13 and 14 which show the two adjustments in the same image. As one might suspect from the names, Highlights adjustments affect a broader range of tones than Whites adjustments.

CompareWhitesHighlights+25

Figure 13. Comparison of Whites and Highlights adjustments to a back-to-white gradient with Camera Raw 8. Both adjustments are +25.

CompareWhitesHighlights-25

Figure 14. Comparison of Whites and Highlights adjustments to a back-to-white gradient with Camera Raw 8. Both adjustments are -25.

Figures 15 and 16 show compare adjustments to Shadows with adjustments to Blacks. In this case, Shadows adjustments affect a broader range of tones than Blacks adjustments.

CompareBlacksShadows+25

Figure 15. Comparison of Blacks and Shadows adjustments to a back-to-white gradient with Camera Raw 8. Both adjustments are +25.

CompareBlacksShadows-25

Figure 16. Comparison of Whites and Highlights adjustments to a back-to-white gradient with Camera Raw 8. Both adjustments are -25.

Camera Raw Adjustments to a Photograph

Let’s try some of these adjustments on an actual photograph. As an example, I’ve selected a photograph of a jackrabbit that was taken in flat light on a cloudy day. The unadjusted photograph is shown in Figure 17.

Jackrabbit_20130630_5754_Original

Figure 17. Unadjusted photograph of a jackrabbit.

To some extent, expose adjustments depend on the tastes of the person doing the adjustments. However, a bit of quantitative information can be gleaned from histograms. The histogram associated with this image is shown in Figure 18. Notice that it’s shifted toward darker tones suggesting that the image may be a bit underexposed.

JackrabbitHistogram_Original

Figure 18. Histogram for the photograph in Figure 17.

Figure 19 shows the effect of setting Exposure to +0.50.

Jackrabbit_20130630_5754_Exposure+050

Figure 19. Photograph of the jackrabbit after Exposure has been set to +0.50 in Camera Raw 8.

Figure 20 shows the histogram associated with the photograph in Figure 19. Increasing the exposure spread out the peak a bit and moved it toward brighter tones.

JackrabbitHistogram_Exposure+050

Figure 20. Histogram for the photograph in Figure 19.

Based on the histogram in Figure 20, Exposure could be increased even more without clipping whites. I tried higher values for Exposure but didn’t care for how bright it made the background. Instead I set Contrast to +20. That made the jackrabbit stand out a bit more by emphasizing the contrasting tones in its coat.

Jackrabbit_20130630_5754_Contrast+20

Figure 21. Photograph of the jackrabbit after Exposure has been set to +0.50 and Contrast has been set to +20 in of Camera Raw 8.

Next I reduced some of the background brightness by setting Highlights to -25. Figure 22 displays the result.

Jackrabbit_20130630_5754_Highlights-25

Figure 22. Photograph of the jackrabbit after Exposure has been set to +0.50, Contrast has been set to +20, and Highlights has been set to -25 in Camera Raw 8.

Finally, I attempted to bring out some more detail in light areas of the jackrabbit’s coat by setting Whites to -15. The resulting adjustments are shown in Figure 23.

Jackrabbit_20130630_5754_Whites-15

Figure 23. Photograph of the jackrabbit after Exposure has been set to +0.50, Contrast has been set to +20, Highlights has been set to -25 and Blacks has been set to -15 in Camera Raw 8.

You can click on the jackrabbit photos to display larger versions that may be easier to compare with each other than those embedded in the text.

One can spend an inordinate amount of time seeking optimal adjustments. I don’t claim that my adjustments are optimal or even that such a thing as optimal adjustments exits, but to my eye the final version is an improvement over the original. Feel free to download the original image and see if you can find better adjustments yourself.

In my next post I’ll discuss the Exposure and Brightness/Contrast adjustments in Photoshop.

Adjusting Exposures, Part 2 — Basic Legacy Camera Raw Adjustments

This post is part of a series of posts on Adjusting Exposures. The series begins here.

The top halves of the black-to-white gradient images in this post show effects of adjustments. The bottom halves show the original image. If you’d like try out adjustments yourself, you’ll find the black-to-white gradient image here.

Legacy Camera Raw Exposure Adjustment

Older “legacy” versions of Camera Raw have a different set of exposure adjustments than newer versions. Figure 1 shows the effect of setting Exposure to +1 in a legacy version of Camera Raw. Grays become lighter, but pure black on the left side is preserved. Figure 2 shows the effect of setting Exposure of the black-to-white gradient to -1 in a legacy version of Camera Raw. Grays become darker. Pure white on the right side of the image is preserved.

GadientDemoBrExposure+1

Figure 1. Black-to-white gradient image with Exposure set to +1 in a legacy version of Camera Raw.

GadientDemoBrExposure-1

Figure 2. Black-to-white gradient image with Exposure set to -1 in a legacy version of Camera Raw.

As you can see, Exposure adjustments in legacy versions of Camera Raw affect mid-tones but leave blacks and whites unchanged.

Legacy Camera Raw Recovery, Fill Light, and Blacks Adjustments

An example Recovery adjustment made with a legacy version of Camera Raw is shown in Figure 3. It darkens light grays without modifying darker grays. The legacy Fill Light adjustment shown in Figure 4 does just the opposite. It lightens dark grays without modifying lighter ones. Recovery can help enhance detail in highlights. Fill Light can help enhance detail in shadows.The Blacks adjustments in legacy version of Camera Raw darkens grays. An example is shown in Figure 5.

GadientDemoBrRecovery+50

Figure 3. Black-to-white gradient image with a legacy Camera Raw Recovery adjustment of 50.

GadientDemoBrFillLight+50

Figure 4. Black-to-white gradient image with a legacy Camera Raw Fill Light adjustment of 50.

GadientDemoBrBlacks+50

Figure 5. Black-to-white gradient with a Camera Raw Blacks adjustment of 50.

Note that values used in these demonstrations were selected to emphasize effects. Appropriate adjustments for typical photographs are generally smaller. Often a combination of adjustments is necessary for best results.

Legacy Camera Raw Brightness and Contrast Adjustments

Figures 8 and 9 show the effects of the legacy Camera Raw Brightness adjustment. In both cases mid-tones are most affected, and darker and lighter tones are least affected.

GadientDemoPsBrightness+50

Figure 8. Black-to-white gradient with Brightness set to +50 in a legacy version of Camera Raw.

GadientDemoPsBrightness-50

Figure 9. Black-to-white gradient with Brightness set to -50 in legacy version of Camera Raw.

Legacy Camera Raw Contrast adjustments shown in Figures 10 and 11 most affect darker and lighter tones and leave mid-tones less affected. Increasing contrast makes darker tones darker and lighter tones lighter. Decreasing contrast makes darker tones lighter and lighter tones darker. In both cases blacks and whites are preserved.

GadientDemoBrContrast+25

Figure 10. Black-to-white gradient with Contrast set to +25 in legacy version of Camera Raw.

GadientDemoBrContrast-25

Figure 11. Black-to-white gradient with Contrast set to -25 in legacy version of Camera Raw.

Clipping Indicators

Clipping occurs when adjustments reduce the range of tones so much that detail is lost in the image. In light areas whites may be “blown out.” In dark areas by blacks may be “crunched.”

Both legacy and newer versions of Camera Raw have useful features for identifying clipping. Clicking the triangle at the upper left of the histogram display switches back and forth between displaying clipped dark colors as either their inherent color or bright blue. Clicking the triangle at the upper right of the histogram display switches back and forth between displaying clipped light colors as either their inherent color or as bright red.

Before opening a photograph in Photoshop, I try to make basic Camera Raw adjustments so there is no indication of clipping in any important areas of the image.

Camera Raw 8 has a different set of basic adjustments. I’ll describe them in my next post.

Adjusting Exposures, Part 1 — Overview

Introduction

These notes were prepared for a presentation to the Mile High Wildlife Photo Club Digital Group on July 25, 2013.

I’m not sure “adjusting exposure” is the best description of what I’m going to cover in my presentation. I think of “exposure” as a global effect that treats all levels of brightness the same way. If exposure is increased when a photograph is taken, both light and dark areas of the image are made lighter. If it is decreased, both light and dark areas of the image are made darker. Usually I want to do more than that in post-processing. For example, I may want to bring out details in dark areas of an image without lightening bright areas. Making such changes is perhaps better described as “adjusting relative sensitivity to light.” That sort of adjustment means more than “exposure” to me, but it’s what I’m going to cover here.

I am, however, going to stick to the theme of “globalness” in one important respect. Except for a passing comment or two, I’m going to ignore one of Photoshop’s most powerful tools: the ability to mask adjustments so they apply only to selected areas of an image.

I’m going to stick to one other ground rule. I’m a firm believer in maintaining original data in my Photoshop files. I don’t know why that is. Many good photographers duplicate background layers of their images and make changes to the copies. Directly editing duplicate layers preserves the original image, but does not provide a lasting record of the changes. I prefer to apply my changes as adjustment layers or as smart filters. These techniques allow parameters to be modified without starting over again.

Although I’ll give examples of specific adjustments, there’s really no substitute for sliding sliders to see an effect. I encourage you to download sample images and try things out for yourself.

Examples versus Photographs

I like simple examples that allow me to see just what an adjustment does. To help visualize adjustments, I’ve created several graphic images. Figure 1, a simple black-to-white gradient, is an example. Some adjustments affect dark tones. Others affect light tones. Still others affect only mid-tones. Looking at an image like Figure 1 before and after an adjustment clearly shows the effect of the adjustment.

GadientDemo

Figure 1. Black to White Gradient Used to Demonstrate Adjustments (Click to get a larger image suitable for downloading for observing adjustments yourself.)

I’ve selected my example graphics so they have identical top and bottom halves. To demonstrate effects of adjustments in these notes, I’ll generally adjust only the top half of graphic images. For example, Figure 2 shows an adjustment that darkens mid-tones of the image in Figure 1.

GadientDemoBrExposure-1

Figure 2. An example showing how adjustments to graphic images will be displayed. The top half of the image shows the adjustment. The bottom half is unadjusted.

Although use of graphic images has advantages, I’ll also demonstrate effects of some adjustments on actual photographs.

Software and Workflow

Examples are based on Adobe Photoshop Creative Cloud. I imagine they are relevant for other relatively recent versions of Photoshop, but I’ve not tried them all. As I noted above, I make non-destructive, documented adjustments in Photoshop by using adjustment layers and smart filters.

Photoshop Creative Cloud and its predecessor Photoshop Creative Suite come with two very useful programs: Bridge for viewing, naming and categorizing images and Camera Raw for manipulating raw image files. Raw image files have special formats tailored to the digital cameras that produce them. Camera Raw handles the transition of raw files to files that Photoshop can manipulate directly. Its adjustments (including cropping) get saved along with changes made by Bridge in either a database or “side-car” .xmp files. These saved changes get processed when images are displayed in Bridge or opened for Photoshop.

Lightroom is another Adobe program that can make non-destructive changes to photographs. Because I don’t use Lightroom, my examples will be from Bridge and Camera Raw. However, I believe Lightroom has many features similar to those I’ll describe.

I normally make most basic exposure adjustments in Camera Raw before opening images in Photoshop. Camera Raw 8, which is distributed with Photoshop CC, allows adjustment of Exposure, Contrast, Highlights, Shadows, Whites and Blacks. Older “legacy” versions of Camera Raw allow adjustment of Exposure, Recovery, Fill Light, Blacks, Brightness, and Contrast. Camera Raw 8 will revert to the legacy set of adjustments for images that have saved adjustments created with legacy versions of Camera Raw.

Raw image files are opened in Camera Raw when you double click on their thumbnails in Bridge. To open JPEGs and a limited number of other file types in Camera Raw from Bridge hold down the Ctrl key while clicking (Mac) or right-click (Windows) the image thumbnail and select Open in Camera Raw… from the menu.

After making Camera Raw adjustments, you can click Open Image button toward the bottom right of the Camera Raw display to open the adjusted file in Photoshop. Clicking the Open Image bottom creates a raster image by performing the Camera Raw adjustments on the original image and then opens the raster image in Photoshop.

If you care to do so (I almost always do), you can hold down the Shift key while clicking open button. The Shift key changes the Open Image button to an Open Object button. Clicking the Open Object button opens a Photoshop Smart Object that contains both the original unadjusted image and the non-destructive Camera Raw adjustments. Clicking on the layer thumbnail image for a Smart Object in Photoshop’s layers menu will reopen the image in Camera Raw. Camera Raw adjustments can then be viewed or modified. Clicking OK after Camera Raw adjustments have been modified saves the new adjustments into the Photoshop Smart Object.

Scope of the Presentation

I plan to discuss primarily Levels, Shadows/Highlights, and Curves in my presentation. However, it seems incomplete to discuss “adjusting exposures” without at least mentioning basic Camera Raw adjustments and the Exposure and Brightness/Contrast adjustments Photoshop. My posts will begin with discussions of these adjustments even though I may not cover them in detail in my presentation to MHWPC. In my next post, I’ll discuss some of the adjustments available in legacy versions of Camera Raw.

Coneflower Critters

Purple Coneflower

Purple Coneflower

I’ve been observing a patch of purple coneflowers in our backyard. The coneflowers themselves are both attractive and interesting. Some people believe that extracts from native coneflowers (a.k.a. echinacea) help fight the common cold. The critters coneflowers attract are fascinating.

Bumble Bee

Bumble Bee

Honey Bee

Honey Bee

Bumble bees and honey bees are regular visitors. I see them almost every time I look in on the coneflower patch. Bumble bees are North America’s only native social bees. Honey bees are, of course, social as well, but they aren’t native. The first honey bees in North American were brought by European colonists in 1622.

Tricolored Bumble Bee

Tricolored Bumble Bee

Even though they are also common, I still get excited when I find a tricolored bumble bee. The band of orange fuzz makes them special.

Sweat Bee

Sweat Bee

Some sweat bees are even more colorful than tricolored bumble bees. Although sweat bees are reputed to be attracted to human sweat, I’ve yet to be bothered by sweat bees while photographing in our coneflower patch. Maybe these small bees are too busy gathering pollen to notice that I sweat profusely while watching them fly from plant to plant under the hot summer sun. Or maybe my camera scares the sweat bees away. They seem much more easily startled by quick movements than bumble bees and honey bees. Only after repeated attempts was I able to get a sweat bee photo that I liked.

Spider Web

Spider Web

The coneflowers host predators as well. I found a spider web connecting three neighboring flowers.

Spider

Spider

Hoping for a meal to come along, a spider waited beneath one of the three flowers connected by its web. While I watched, both a sweat bee and honey bee got stuck in the web. They flailed frantically before managing to escape.

Dead Honey Bee

Dead Honey Bee

Another honey bee appeared to be the victim of a different predator. The insect at the top of the photo may be an assassin bug. If it is, it probably killed the honey bee. The half dozen flies on the bee’s corpse are probably flesh flies. The flies are difficult to see in this small photo. In fact, I didn’t notice them myself until I looked at full-sized version of the photo on my computer screen.

Dead Honey Bee Detail

Dead Honey Bee Detail

In the detail I count four flies on the left side of the bee, one and possibly another on the right side, and one that’s difficult to pick out in the middle. To find the flies, it helps to look for their prominent brick-red eyes.

Bee Fly

Bee Fly

Flies on the dead bee weren’t the only flies in the coneflower patch. Bee flies are regular visitors. Bee flies look and behave much like bees, but, like other flies, they have only a single set of wings. Bee flies tend to hold their wings out while resting.

Green Bottle Fly

Green Bottle Fly

On one occasion, a green bottle fly perched on a down-hanging coneflower petal. Bottle flies are attracted to decaying flesh, decomposing organic matter, and foul-smelling plants. I imagine this fly was a casual visitor not specifically attracted to the coneflowers. While I was watching, it perched on the petal grooming itself and didn’t go near any of the flower heads that attracted the bees. The petal was probably just a convenient place to land.

Thread-waisted Wasp

Thread-waisted Wasp

One day a thread-waisted wasp came along and suspended itself from a coneflower leaf just long enough to have its picture taken. I imagine it was a casual visitor as well. Thread-wasted wasps seem to be more attracted to mint plants flowering nearby than they are to the coneflowers.

Peck's Skipper

Peck’s Skipper

Occasionally, Butterflies take apparently random routes among the flowers in our yard. They seem to have difficulty figuring our where to land. When they do land, butterflies usually don’t stay long. This Peck’s skipper was an exception. It landed on a nearby coneflower. I managed to get several photographs before it flew away.

I’ve traveled thousands of miles to photograph wildlife. I’m delighted to have found such a rich source of new things to photograph just a few steps from our backdoor.


Copyright © 2011 Robert N. Stocker. All rights are reserved. Please contact us for additional information.

If you enjoyed this posting you may want to visit our small, but growing gallery of insect photos. We aren’t entomologists. Please contact us if you come across anything we have misidentified.

Too Big to Swallow

 

On March 29 I spent the afternoon photographing birds from the boardwalks at the South Padre Island Birding and Nature Center in Texas. As the light was waning, I noticed a Great Blue Heron standing beneath one of the boardwalks.

Great Blue Heron Standing Beneath a Boardwalk

Great Blue Heron Standing Beneath a Boardwalk

It didn’t seem to be fishing, but I suppose herons rarely ignore a nearby fish. This one certainly didn’t. Fifteen seconds later it plunged into the water…

Great Blue Heron Catching a Fish

Great Blue Heron Plunging After a Fish

and came up with an astonishingly large fish!

Great Blue Heron with a Fish

Great Blue Heron with a Fish

I’m often amazed by some of the things that birds can swallow, but this fish seemed too big for even the most determined heron. Apparently the heron thought so too. The heron carried the fish away from the water…

Great Blue Heron Carrying a Fish

Great Blue Heron Carrying a Fish

and dropped it.

When I left the Birding and Nature Center several minutes later, I walked across the boardwalk under which the heron had been standing. The fish lay dying on the mudflat below.

Early the next morning I returned to the spot where the heron had dropped the fish. The fish was gone. I had expected to see fresh seagull tracks, and was surprised to find these tracks instead.

Tracks in the Mud

Tracks in the Mud

Later in the morning I noticed a fish head lying on the mud about twenty meters from the spot where the heron had dropped the fish.


Copyright © 2011 Robert N. Stocker. All rights are reserved. Please contact us for additional information.

Diamondback Water Snakes

Recently, I nearly missed some interesting wildlife behavior that was happening right in front of me.

On an overcast morning in late March 2011, I took a number of unremarkable photographs of distant subjects like Little Blue Herons, Neotropic Cormorants, Great Egrets, Least Grebes and Snowy Egrets from the edge of a pond in Santa Ana National Wildlife Refuge near Alamo, Texas. Only after having been at the spot for nearly half an hour did I notice a Diamondback Water Snake stretched out on a log right in front of me.

Diamondback Water Snake

Diamondback Water Snake

Almost immediately, I noticed a second snake stretched out on an even closer log. A third snake then emerged from the water near the second snake’s head…

Diamondback Water Snakes

Male Diamondback Water Snake Beginning to Crawl Down a Female’s Back

and began to crawl down the second snake’s back…

Diamondback Water Snakes

Male Diamondback Water Snake Crawling Down a Female’s Back

until it came to the end of the log.

Diamondback Water Snakes

Male Diamondback Water Snake Stretched Out Along a Female’s Back

Diamondback Water Snakes are nonvenomous snakes that give live birth from fertilized eggs retained in females’ bodies. Females are noticeably larger than males. Based on size, the first two snakes were females, and the third was a male.

After a few minutes of indecision, the male snake slipped off into the water, turned around and crawled up the back of the female in the opposite direction.

Diamondback Water Snakes

Male Diamondback Water Snake on the Back of a Female

Once the male snake was stretched across the back of the female, neither snake moved appreciably for twenty minutes or more.

By this time, a crowd had gathered. Some people seemed more interested in chatting with each other than observing nature. Feeling frustrated with the crowd and thinking that the best of the show was over, I left.

I returned to the site after half an hour. The crowd had moved on, but the snakes were still there.

Diamondback Water Snakes

Male Diamondback Water Snake Coiled on Top of a Female

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