Today’s Question: With some photos when I use the clipping preview while adjusting the Blacks, I see an odd behavior. Usually when I drag the Blacks slider to the white, the pixels gradually disappear until there is no clipping. Sometimes, however, nothing seems to happen for a while, and then all of the pixels that appear clipped disappear all at once. Why does this happen, and should I be concerned about it?
Tim’s Quick Answer: The issue here is that the detail is clipped in the original capture, and thus can’t be recovered. I would therefore tend to set the Blacks value to the point right before all of the pixels disappear in the clipping preview display.
More Detail: The Blacks and Whites sliders found in Adobe Camera Raw, Lightroom, and other software for optimizing photos, is designed to enable you to establish the white point and black point for an image. In theory, that means you would increase brightness for the brightest pixels in a photo so that the brightest pixel is white or nearly white, and similarly darken the darkest pixels to produce a true black.
Of course, in some cases the black and white values may have already been clipped in the original capture, meaning detail was lost in those areas based on the original exposure.
When using RAW capture, the initial black and white point values may reflect clipping based on the default interpretation of the capture data, but you may be able to recover what appears to be lost detail by refining the adjustments for the black and white points.
However, while it is indeed possible to recover “lost” detail for a RAW capture by refining the black and white point adjustments, there are limits to what is possible. If the information was truly lost, meaning texture in the brightest or darkest areas of a scene was truly lost, that information can’t be recovered.
For example, if you include the sun in the frame but the exposure settings were such that the sun was completely blown out with no detail, you can’t recover texture in the sun. You may be able to darken the pure white texture to be a pure gray texture, but you can’t actually recover texture variations if the information wasn’t included in the original capture.
In a situation where some detail was lost in the brightest or darkest areas of a photo, in general I prefer to set the black or white point adjustment to the point just before the details is recovered, reflecting the actual clipping that occurred in the original capture while preserving as much detail and contrast as possible. Naturally you will want to fine-tune these adjustments based on the specific image and your preference for how to interpret the image.