Contrast Continued
After a brief interlude discussing histograms and pixel leakage, we can return to the middle C of our Crop, Contrast and Color, discussion.
In Part 4, we worked on getting our image exposed properly. As with anything in digital photography, getting it right in the camera is always preferable. Sometimes circumstances dictate that you will have to make an overall exposure correction. We will assume that is completed.
Adobe Lightroom Adjustments
After getting the overall brightness or darkness of an entire image adjusted to scene or to taste, I usually turn to my shadows and highlights. If you are editing your image in a RAW conversion tool, many have a highlight recovery tool to help you recover subtle detail in the highest exposed portion of the image. I normally adjust this first-carefully watching for changes to parts of the image which I don't consider highlights but may change none-the-less.
Photo Paint Brightness Contrast Tool
Without benefit of a RAW Converter, you are likely going to be working initially with a Brightness/Contrast Control to make certain your highlights are not blown completely to white.
After making certain my highlights are as close to white as possible without large portions of the image going to white, I begin to work on the shadows and black portions of an image. Now, I want to caution you not to take your exposure up on every image to ensure the image's highlights go to white. That isn't always necessary or desirable. Some photos have no part of the scene brighter than gray and it is acceptable to leave the brightest portion of the image at a realistic setting. Otherwise, you will run the risk of making an image look blatantly artificial.
 | In this shot of center-pivot irrigated fields taken from an airplane, you can see the image is flat. There is nothing remotely close to white in the scene. The histogram bears this out as well. Most of the tones fall in the middle of the histogram and there are a smattering of highlights and almost no shadows. It would be foolish to push this image's brightest areas to white just because 'highlights should be bright' |
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This is a case where it is expected that you will evaluate the image and realize that the exposure is pretty good and that pushing or pulling of the overall histogram is not required. |
But, as I said earlier, I go after the shadows next. The shadows of my crop circles image are a little flat. The light, the haze in the air and shooting through the several-layered window have conspired to create a washed out image. In this scene I am fairly certain there are areas which should be darker. So I will adjust the black point, either using the RAW dialog above or using a Level Adjustment (Adobe Photoshop, PSP) or a Contrast Enhancement (Corel PhotoPaint).
 | Pulling the Shadows Slider boosts the contrast of the image. The Shadows are closer to black.
I increased the exposure slightly to balance the image and the resulting histogram shows the range of the image has increased from just over one F-Stop to three and one half. |
The temptation to drag the darkest part of your histogram to complete black is difficult to resist. Major contrast and dark shadows give mood and drama to an image. It is a 'taste' thing. Deep the dark tones to your taste but don't be afraid to back off your adjustment and see if you can find a reasonable setting.
Photoshop Levels Controls
You will notice, too, in the adjusted crop circle image that the colors have been saturated as a result of dragging the shadows toward black. This is why I don't adjust color first. Now that contrast has allowed more saturated colors to appear, I can see color casts and color deficiencies that were hidden in the flat image above. We will go after them later.
PhotoPaint Contrast Enhancement Control
(Note that adjustments are made on the top side of the histogram-unlike Photoshop where sliders are on bottom of the histogram)
Now that I am satisfied with the overall exposure of the image and the placement of the darker shades in the shadows, I can begin to tackle the mid-tone contrast. Even though Levels and Contrast Enhancement commands allow you to adjust position of the mid-tones via the Gamma Control, I almost never use this adjustment. I prefer to adjust my mid-tone contrast independently so that I can gain finer control.
Those mid-tones will have to wait for the next installment.
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