Today’s Question: I’ve been trying to get more familiar with the various adjustment options in Lightroom Classic, including with the Crop tool. For the life of me I can’t figure out what the “Constrain to Image” checkbox does, as it doesn’t seem to impact my cropping whether it is on or off. Does this checkbox do anything?
Tim’s Quick Answer: The “Constrain to Image” setting for the crop tool in Lightroom Classic ensures that the crop only includes the actual image area of your photo. It only actually applies if you have applied an adjustment (such as a Transform adjustment) that causes there to be white space outside of the original image area.
More Detail: If you haven’t done anything to alter the actual shape of a rectangular photo, the “Constrain to Image” checkbox won’t have any impact on the behavior of the Crop tool. In other words, if you don’t see any “extra” white space around your photo, the “Constrain to Image” feature doesn’t apply.
If you had, for example, applied some of the adjustments found in the Transform section of the right panel in the Develop module, the overall shape of the image may have been altered to the point that some white space appears around portions of the edge of the image.
For example, the Vertical slider allows you to tilt the image toward or away from you, to correct for perspective issues. With even a small adjustment, you’ll see white triangles appear at the top or bottom corners of the image, depending on whether you apply a positive or negative value for the adjustment.
If such white space appears around the edges of the image, turning on the “Constrain to Image” checkbox for the crop tool will ensure that the crop box can never extend beyond the actual image area, causing any of those white boundary areas to be cropped out of the image.
You can, of course, simply manually make sure that the crop box remains inside the actual image area, but the “Constrain to Image” checkbox makes it easy to ensure you don’t miss a small area, creating what would effectively be a blemish along the edge of the photo.