From an expert: Shadows/Highlights
The Shadow/Highlight command is one method for correcting photos with silhouetted images due to strong backlighting or correcting subjects that have been slightly washed out because they were too close to the camera flash. The adjustment can also be used for brightening areas of shadow in an otherwise well‑lit image. The Shadow/Highlight command does not simply lighten or darken an image; it lightens or darkens based on the surrounding pixels (local neighborhood) in the shadows or highlights. For this reason, there are separate controls of the shadows and the highlights. The defaults are set to fix images with backlighting problems.
The Shadow/Highlight command also has a Midtone Contrast slider, Black Clip option, and White Clip option for adjusting the overall contrast of the image, and a Color Correction slider for adjusting saturation.
(Optional) Click the Save As Defaults button to save your current settings and make them the default settings for the Shadow/Highlights command. To restore the original default settings, hold down the Shift key while clicking the Save As Defaults button.
You can reuse Shadow/Highlight settings by clicking the Save button to save the current settings to a file and later using the Load button to reload them. For more information on saving and loading settings, see Save adjustment settings.
Controls (separately for the highlight and shadow values in the image) how much of a correction to make.
Extreme Amount values may lead to a crossover, where what started as a highlight becomes darker than something that started as a shadow; this can make the adjusted images look ‘unnatural’.
Controls the range of tones in the shadows or highlights that are modified. Smaller values restrict the adjustments to the darker regions for shadow correction and the lighter regions for highlight correction. Larger values increase the range of tones that are adjusted further into the midtones. For example, at 100% the shadow tonal width slider affects the shadows the most, the midtones are partially affected, but the brightest highlights are not affected. Tonal width varies from image to image. Too large a value may introduce halos around dark or light edges. The default settings attempt to reduce these artifacts. Halos may also occur when the Shadow or Highlight Amount values are too large.
Tonal Width is set to 50% by default. If you find that you are trying to lighten a dark subject but the midtones or lighter regions are changing too much, try reducing Shadow Tone Width toward zero so that only the darkest regions are lightened. If, however, you want to brighten the midtones as well as the shadows, increase Shadows Tonal Width toward 100%
Controls the size of the local neighborhood around each pixel. Neighboring pixels are used to determine whether a pixel is in the shadows or highlights. Moving the slider to the left specifies a smaller area, and moving it to the right specifies a larger area. The optimum local neighborhood size depends on the image. It’s best to experiment with the adjustment. If the radius is too large, the adjustment tends to brighten (or darken) the whole image rather than brightening the subject only. It’s best to set the radius to roughly the size of the subjects of interest in the image. Experiment with different Radius settings to obtain the best balance between subject contrast and differential brightening (or darkening) of the subject compared to the background.
Adjusts the brightness in a grayscale image. This adjustment is available only for grayscale images. Moving the Brightness slider to the left darkens a grayscale image, and moving the slider to the right lightens a grayscale image.
Adjusts the contrast in the midtones. Move the slider to the left to reduce the contrast and to the right to increase the contrast. You can also enter a value in the Midtone Contrast box. A negative value reduces contrast, and a positive value increases contrast. Increasing midtone contrast produces greater contrast in the midtones while tending to darken the shadows and lighten the highlights.
Black Clip And White Clip
Specifies how greatly the shadows and highlights are clipped to the new extreme shadow (level 0) and highlight (level 255) colors in the image. Larger values produce an image with greater contrast. Be careful not to make the clipping values too large, because doing so reduces detail in the shadows or highlights (the intensity values are clipped and rendered as pure black or pure white).