Today’s Question: Is it necessary to save a selection [in Photoshop] if I’m going to create a layer mask based on the selection? Wouldn’t saving the selection in this case be somewhat redundant?
Tim’s Quick Answer: In general I would say that it isn’t necessary to save a selection using the “Save Selection” command if you’re going to create a layer mask based on that selection. After all, the layer mask also represents what is essentially a saved selection.
More Detail: However, there are situations where you may want to save a selection.
For example, if you will be building up a somewhat complicated selection in a series of steps, it can be helpful to save a series of selections and then merge those together into the final selection. In addition, you may find that in some cases you apply a variety of adjustments directly to a layer mask, causing changes compared to the original selection you used as the basis of that layer mask. In this type of situation you may want to save the initial selection before using that selection as the basis of a layer mask.
For most photographers and in typical workflow scenarios, however, I would say that it probably isn’t necessary to save a selection if you’re simply going to be using that selection as the basis of a layer mask. Of course, it is also worth noting that a saved selection won’t significantly increase the file size, so there isn’t significant harm in erring on the side of caution and saving selections as part of your master image files.
In those cases where you do decide to save a selection, you can simply choose Select > Save Selection from the menu to initiate the process. Enter a name for the selection in the Save Selection dialog, and click OK to save the selection as an alpha channel. As long as you then save the image as a Photoshop PSD or TIFF file, the saved selection will be included as part of the file.