Motivation: Photoshop has some masking
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
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
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
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
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 firstname.lastname@example.org.
Overview (c)JBSurveyer 2006