Today’s Question: You’ve talked about using the Alt/Option key to enable a clipping preview when adjusting tone for a photo in Lightroom Classic. But why not just click the triangles at the corners of the histogram so the clipping preview display is always on?
Tim’s Quick Answer: While the clipping preview options associated with the histogram in the Develop module of Lightroom Classic can be helpful, it doesn’t provide as much detail related to clipping compared to holding the Alt/Option key while applying an adjustment.
More Detail: Clipping refers to the loss of detail for the darkest shadows or brightest highlights for an image. A clipping preview display can help you decide on the specific adjustments you’ll apply to an image to avoid the loss of detail in the darkest and brightest areas of a photo.
At the top corners of the histogram at the top of the right panel in the Develop module you’ll find triangles representing the clipping preview feature. The triangle at the top-left represents black clipping, and the triangle at the top-right represents white clipping.
You can hover the mouse pointer over one of these triangles to see a clipping preview overlay in areas of the image where detail is being lost based on the exposure and the current adjustment settings. You can click on a triangle to turn the clipping preview on so the overlay remains until you turn the feature off.
However, the clipping preview associated with the histogram does not provide as much detail as you get when holding the Alt/Option key while applying a tonal adjustment. The histogram clipping preview only shows the overlay in areas that have clipped to pure black or white based on all three channels. The clipping preview associated with the Alt/Option key shows you clipping on a per-channel basis, so you can see areas that are losing detail on only one or two channels, not just areas that are clipped on all three channels.
Having this additional level of detail can be helpful to ensure you are not losing too much detail in a photo when applying tonal adjustments. For example, for a photo of a red rose you may lose considerable detail in the red channel before you reach the point where all three channels have been clipped. The detail on the red channel would be very important in this context, and so I would want to have the benefit of a preview that illustrates clipping for each channel individually, not just when all three channels get clipped.