Motivation: Photoshop has some masking problems
Features: They stem from the way Photoshop feathers to the inside on masks

In the past few weeks we have discovered that Adobe Photoshop does not quite apply a mask when feathering is in use the way one would expect it to. First, the edge of the mask appears to form the midway point of the feather - instead of the outer boundary that one might expect. Second, edges on feathered masks are rounded much more than one would expect sometimes. And third, when the mask is drawn to the edge of the image - one would not expect any feathering but the full mask would extend to the edge of the image. But Photoshop feathers to the edge - again, not quite what one anticipates. And though we have looked all over for some alternate settings or options in Photoshop, none appears available.
Masking is tricky business in the first place - just to trace the outlines of a figure can be quite demanding. However, there are other problems such as effect outlines when the user fails to feather the mask so that an effect is blended gradually into the surroung areas.Many photofinishers feather the mask so that unsightly correction edges are not left on the image. But because Photoshop applies the feather to the inside of the image the results can be unexpected as shown in the screenshot immediately below and the next one following:

The corners of the mask are rounded. In the upper right we want the mask to be flush with the edge or border of the image. Also all along the border we do not want any feathering to be applied. But Photoshop applies the feathering to the inside of the mask. So the fix is simple. Just trace along the images edges a second added mask of 0 pixels feather size and about as thick as the original feather size (50 pixels in our case). This remasking (be sure to have chosen the add mask icon in Photoshop's property bar) will then extend the full effect right to the edge/border of the masked part of the image.

However when we tried some color Hue changes we got an unwelcome surprise:

Here we see that the mask is neither fish nor fowl. The effect does not extend to the mask edge - this is expected. But the effect appears to spill out over the edge of the border - and for more than the 50 pixels of our mask feather. So it appears the mask trace line is some average position for the mask. this makes visually checking the mask difficult.

In contrast, check what PaintShop Pro does for a mask with feather:

first their is no rounding of the mask at the corners. The way Paintshop Pro masks with a feather set is to show users while tracing a blue line which is the outer limit of the full mask. Then when the mask is finished, PaintShop pro extends the mask's chain-link border to the limit of the mask+feather. No applied effects will extend beyond these borders. Now this is much closer to the way I want my masks to work. It would be nice to be able to specify a fall-off curve for the feathering region - but I am not greedy.

In the meantime, masking with feathering in Photoshop is problematical. I hope to have some workarounds beyond remasking with 0 pixels at the edges in the next few weeks. Any helpful suggestions should be sent to jbsurv@thephotofinishes.com.