Hey there MM,
I have a question thats been bugging me for quite a while.
When I make a solid selection (by solid I mean there is no feathering at all) of a solid object and invert that selection and make a mask it leaves a sort of fringe where the 'marching ants' were. Even when the marching ants arent there but I invert the mask its still the same.
Is this happening only to me?
Apparently its caused by the anti aliasing but still...
Here is a sample image made with difference blend mode.
I know enough ways to get around it...I just wonder why I have to
Apr 17 13 02:31 am Link
Fairfax, Virginia, US
There are a few things which are likely contributing to this, and AA is certainly one of them. It may be easiest to diagnose if you can describe how you created the image above? (Step
by step so we can directly replicate).
Apr 17 13 03:32 am Link
- new document, white, 300 dpi (16 bit I think)
- solid color adj layer with bright green (no mask yet)
- circular selection AA checked
- on a new layer filled the selection with dark blue
- kept the selection and made a mask for solid color adj layer
- inverted the mask ( I can already see the whites from the bg)
- merged visible on top. set to difference
- disabled the mask for the solid color adj and the halo/fringe became visible as seen.
(I tried inverting the selection and then making the mask but still the same)
will edit if I remember anything else...
Apr 17 13 03:41 am Link
Asheville, North Carolina, US
Hey there Koray, been a while!
After you make your selecting, invert the selection (cnt+shit+I), then select>modify>contract, then choose 1px. This should correct the innate contracting from inverting the selection and get rid of the "shaved off" soft edge.
Apr 17 13 09:26 am Link
well, with AA this simply has to happen, as, by definition, it makes parts of the edge of any non-rectangular shape, or any selection based on it, semi transparent ...
Apr 17 13 09:37 am Link
Found CS2 on my old laptop and its still the same...which means I'm already used to this
Normally I make paths a few pixels inside the edges so I can feather 1 px and compensate for the invert plus the contract mentioned above or use the masking panel etc. but lately I've been a little lazy and all
I just wanted to make sure its not only me and/or there is a clickable little box somewhere that can fix this
Apr 17 13 10:07 am Link
I'm only half skimming this but my guess is it would work in a linear gamma situation, even with AA, but when it's in another gamma the alpha and the 1-alpha don't add up to 1.
Apr 17 13 11:06 am Link
Edit > Color Settings > Advanced Controls
UNCHECK blend colors with gamma 1.00 and Koray's setup works okay for me. Which is weird to me.
I think it's a color space gamma interaction thing.
Apr 17 13 11:14 am Link
okay -- I think I got it.
Koray's setup works fine but the bottom layer can't be left white. It has to be black for the math to work.
Linear gamma mixing, but make the bottom layer under the masked green layer black.
Apr 17 13 11:18 am Link
Bottom layer white
Bottom layer black
Apr 17 13 11:25 am Link
well now thats interesting
Apr 17 13 11:36 am Link
Tarragona, Catalonia, Spain
Yeap!! & Weird!!
Apr 17 13 11:41 am Link
San Jose, California, US
I've always come across this and usually end up doing the expand selection as a fix. I was curious about the opacity and it looks like it caps out at 25%. Maybe it is an issue with rounding and splitting the difference?
Apr 17 13 11:52 am Link
Internos Photography wrote:
Apr 17 13 01:27 pm Link
Apr 18 13 01:13 am Link
A layer mask multiplies itself by the associated layer, its inverse by the underlying composite below, and adds the two.
Transparencies fit perfectly.
Apr 18 13 01:41 am Link
Apr 18 13 01:57 am Link
http://jfrancis.smugmug.com/photos/i-ks … sRkPxQ.jpg
(Positive masked green over black) + (Negative masked blue over black)
where + is linear dodge (add)
and color blending at gamma 1.0 is set off
(why off and not on I'm not sure)
Apr 18 13 02:12 am Link
Apr 18 13 03:43 am Link
Well, yes. Masking an already masked thing is a recipe for matte lines. I wrote about it extensively in those decade-old links above, but it's been known since at least the 80s, and much earlier than that in film opticals.
Apr 18 13 09:44 am Link
And there are no 'transparencies.' There are only color values and and extra alpha channel, and what gets done with them generally falls into two categories.
Apr 18 13 09:59 am Link
And when it comes to the appearance of the cor blending at the mask edges, things like gamma do actually matter.
Apr 18 13 10:06 am Link
I am totally lost
Apr 18 13 01:56 pm Link