Today’s Question: Sometimes I want to add more canvas to an image I have previously cropped [in Photoshop] and my first go-to is the “Reveal All” command. In some cases, this results in a layer mask that does not apply to the newly revealed image area. Is there some way to ensure the effects of the extra canvas from “Reveal All” always shows the full effect of all adjustment layers?
Tim’s Quick Answer: The issue of an incomplete mask that you describe occurs in a specific situation when you have created a layer mask after the image has been cropped in Photoshop, and where that layer mask causes an adjustment to apply all the way to the edge of the cropped image. If you then reveal all (or some) of the cropped image, you’ll need to manually fill in the mask in the area outside the cropped version of the image.
More Detail: When you crop an image in Photoshop you have the option to turn off the “Delete Cropped Pixels” checkbox on the Options bar for the Crop tool. When you crop with this checkbox turned on, you’re not removing the cropped pixels from the image, but rather are reducing the canvas size to hide portions of the image.
If you apply a targeted adjustment using an adjustment layer with a layer mask to change the appearance of a portion of the image, in most cases if you then use the “Reveal All” command to reveal the cropped portion of the image, there won’t be any problematic effect. That’s because in many cases a targeted adjustment will apply to only a portion of the image without extending all the way to the outer edge of the image. In this case the outer perimeter of the layer mask is filled with black, and when you expand the canvas that additional area of the mask will also be filled with black.
If, however, a targeted adjustment applied to a cropped image does extend all the way to the edge of the image, there will be white in those areas of the layer mask. If you then expand the canvas, the area outside the cropped image will be filled with black on the layer mask, so that the adjustment is not applied. However, this will create an obvious boundary between the original targeted adjustment and the rest of the image. You could create a selection of the applicable area of the layer mask and fill it with black to resolve the issue. If possible, however, I recommend applying all targeted adjustments before cropping, so that if you later decide to expand the canvas to undo some or all of that crop, there won’t be any need to modify any layer masks for the image based on that canvas expansion.
