2019.x

Guiding Principles for Color Correction
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Correcting Tonal Range
Correcting the tonal range usually requires two steps. First, you reset the white and black points to
make the range of values between the lightest part of the image and the darkest part of the image as
large as possible. Second, you adjust the gray point to control how much of the total tonal range falls
above and how much below the middle value.
Setting White and Black Points
Setting the white point and the black point is simple when a shot includes an area that should
obviously be very light and another area that should be very dark. You look for what should be the
lightest area of the image and adjust controls until it becomes as light as possible, and then do the
same for the area that needs to be black. You can dramatically improve the quality of shots taken
using insufficient or excessive light just by making white and black point adjustments.
In some cases, however, the shot should have a smaller brightness range (for example, when the
whole scene was originally in shadow or was shot at sunset). In such cases, you need to be careful to
expand the range as much as possible without making parts of the image unrealistically light or dark.
Do not clip any significant part of the image. You want the range between your lightest value and
your darkest value to be as large as possible, but you don’t want to lose detail by reducing all your
very light values to white or all your very dark values to black.
Do not use intense reflected spots of light — speculars — to judge where your white point should be.
If you do so, you define white by an artificial standard that probably occurs in only a tiny fraction of
the image. A true white object such as an item of clothing might appear dull and gray by this
standard.
You have a number of choices for controls to use to make white point and black point adjustments,
including the Gain and Offset sliders in the Hue Offsets subdividing tab of the HSL group and the
Master curve in the Curves tab. You can set all of these controls automatically using the Auto Black,
Auto Contrast, and Auto White buttons. If necessary, you can begin with an automatic correction and
then fine-tune the adjustment manually.
() You have a number of choices for controls to use to make white point and black point adjustments,
including the Gain and Setup sliders in the HSL tab and the various controls in the Levels tab.
Adjusting the Gray Point
Once you establish the range from the brightest part of the image to the darkest part, you can adjust
the gray point if necessary. When you make a gray point adjustment, you define how much of the
overall tonal range is between black and midgray, and how much is between midgray and white.
The most obvious effect of a gray point adjustment is that it either lightens or darkens the overall
look of the image. Large adjustments of the gray point toward either the black point or the white
point are almost always undesirable because they leave the whole image much too dark or too light.
Smaller, well-chosen gray point adjustments, however, are useful for fine-tuning the overall
brightness of the image. Also, because a gray point adjustment expands the tonal range on one side of
the midpoint and contracts it on the other, it can be useful for improving contrast and detail overall.
For example, some images look better if more contrast is available in the range between gray and
white, even though this reduces the contrast between gray and black.
The main control for making gray point adjustments is the Gamma slider in the HSL group.