Today’s Question: I know if I adjust the Masking slider for sharpening [in Lightroom Classic or Camera Raw], the sharpening will only affect the area shown in White. Does this work regardless of whether or not I hold the Alt/Option while adjusting the Masking slider?
Tim’s Quick Answer: If you increase the value for the Masking slider when sharpening in Lightroom Classic or Camera Raw, the sharpening will indeed be confined to the areas shown in white when you hold the Alt/Option key. You don’t have to hold the Alt/Option key at all to have the sharpening constrained in this way.
More Detail: When adjusting the sharpening settings in Lightroom Classic or Camera Raw, you can hold the Alt key on Windows or the Option key on Macintosh to enable a preview that can make it much easier to choose the right settings for each of the sliders. Holding the Alt/Option key will cause the preview image to appear as a black and white image when adjusting the Amount slider, an embossed view when adjusting Radius or Detail, and a black and white masking preview when adjusting the Masking slider.
Holding the Alt/Option key has no impact on the actual adjustment being applied. The only difference is that the preview changes when holding the Alt/Option key. In other words, if you knew which setting you wanted to use for a given slider, or you simply want to use a normal preview when adjusting the sharpening settings at all, you don’t have to hold the Alt/Option key.
I personally find that holding the Alt/Option key can be tremendously helpful in deciding what setting to use for the various sharpening sliders, but this is only a tool aimed at helping find the right adjustment settings. The actual effect of sharpening in the image is not altered based on whether or not you held the Alt/Option key at any time while adjusting the slider values.