Today’s Question: In response to your answers about setting the black point and white point to avoid clipping, would the same concept apply with the Levels adjustment in Photoshop?
Tim’s Quick Answer: Yes, you can compensate to some extent for clipped highlights or shadows with the Levels adjustment in Photoshop. You would just need to use the Output Levels sliders for this purpose, because the sliders for the black and white point don’t allow for a “negative” value.
More Detail: As noted in the past two installments of the Ask Tim Grey eNewsletter, in Camera Raw or Lightroom Classic you can set the black point and white point for a photo with the Blacks and Whites sliders, respectively. If an image exhibits lost shadow or highlight detail in the original capture, you can use a negative value for Whites to tone down the blown highlights, and you can use a positive value for Blacks to brighten up the clipped shadows.
In other words, you can use a positive value for Whites to brighten the brightest pixels, and a negative value to darken those areas. You can similarly use a negative value for Blacks to darken the darkest pixels, or a positive value to brighten those areas.
If you’re using the Levels adjustment in Photoshop you set the black and white point using the Input Levels sliders. Those sliders are found directly below the histogram, with the black value at the far left and the white value at the far right. Normally you would move these sliders inward to set the black and white point for the image, holding the Alt key on Windows or the Option key on Macintosh to enable the clipping preview display while doing so.
However, if the image has clipped shadow or highlight areas based on the original exposure, you wouldn’t want to bring the black or white Input Levels sliders inward. Instead, you would need to use the Output Levels sliders to brighten the shadows or darken the highlights.
If you drag the black Output Levels slider to the right, you are brightening the value for black, so that the darkest areas of the image would be brightened. If you drag the white Output Levels slider to the left, you are darkening the value for white, so that the brightest areas of the image would be darkened.
If there is no detail in the original capture due to clipped shadows or highlights, it is important to keep in mind that adjusting the value for the Output Levels sliders won’t magically bring back the detail in those areas. You will therefore generally want to use a very modest setting for the Output Levels sliders, so that you don’t create a bigger problem with a muddy appearance in the darkest shadows or brightest highlights.