Today’s Question: Can you explain the difference between the Highlights and Whites sliders [in Lightroom Classic or Adobe Camera Raw]? Under what circumstances would you use one rather than the other?
Tim’s Quick Answer: The Whites slider is used to establish a white point for the image, affecting the brightest pixels the most. The Highlights slider enables you to brighten or darken the relatively bright areas of a photo, focusing on a range of tonal values darker than the range the Whites slider focuses on.
More Detail: You can think of the Whites slider as enabling you to set the value for white in the image. The emphasis is on a relatively narrow range of the brightest pixels in the photo. For a typical photographic image, you would adjust the Whites slider so that the brightest pixels in the image are at (or nearly at) pure white. Of course, for images where you don’t want a true white, you could use a lower value for the Whites slider.
The Highlights slider affects a wider range, emphasizing the effect on tonal values that are darker than those affected by the Whites slider. Naturally there is overlap between the effect of these two sliders, but the differences mean that the Highlights slider is really more about emphasizing or toning down bright highlight textures.
For example, you might typically use a value for Whites that causes the brightest pixels in the image to be pure white. This might cause some of the bright highlight areas to look too bright, without much visible texture. Reducing the value for Highlights will both darken those bright highlights, and also add a bit of contrast to enhance texture and detail.
The same basic concepts apply at the other end of the tonal range, with the Blacks and Shadows sliders. In my opinion, all four of these sliders should be reviewed and possibly refined for every image you optimize in Lightroom Classic or Camera Raw.
Note that you can hold the Alt key on Windows or the Option key on Macintosh while adjusting these sliders to get a clipping preview that enables you to see whether (and where) you are losing detail in the image based on the adjustments.