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Photoshop mask question

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  #1  
Old 02-02-2003, 02:24 PM
gonzo gonzo is offline
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Photoshop mask question

Hi,

This has been driving me nuts trying to figure out in Photoshop. I used to use an alpha channel as a mask with my old software. What I want to do specifically is to use the 8 or 16 bit per channel luminescence gradation of an image as a mask upon another image. But I can't figure out how to copy anything into a linked mask, I can only figure out how to do regular painting in the mask. Whenever I try copying something it just pastes into a new layer, not into the linked mask. I thought maybe the solution was to copy into a new alpha channel, but I don't know how to use the alpha channel as a regular mask..

Is this making any sense? If not I'll try to reword it.

As a sidebar, is there an easy way that I can do multiple, 100% opacity, gradations using the gradient tool? Normally, when filling a layer with a gradient, doing the same thing again from a new angle erases the old gradient rather than adding to it. I can only add by either lowering the opacity (even when using 'transparency to colour) or using multiple layers...
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Old 02-02-2003, 02:32 PM
gonzo gonzo is offline
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oops

Duh! Nevermind the last gradient question, I looked in the FAQ forum here and found the 'adding to gradient' answer there.. a little counterintuitive, but it works
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  #3  
Old 02-02-2003, 02:39 PM
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DannyRaphael DannyRaphael is offline
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Gonzo:

Welcome to RetouchPRO. Congrats! You've just broken the all-time record for answering your own question! Well done.

By all means keep asking these good questions. Judging by the content of your first one, I'd say you are well qualfied to answer many, too. Don't hesitate to do that. We always appreciate it when those with knowledge and experience are willing to help out.
Again, welcome. If you haven't seen the RP site map yet, click the link below my signature. Picture sometimes worth 1K words.

~DannyR~
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Old 02-02-2003, 02:43 PM
gonzo gonzo is offline
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Thanks for the welcome. I only answered the gradient question myself though I still haven't figured out how to copy pictures into masks.. can you help? It's such a simple, obvious thing, I used to do it *all the time* with my old gfx program, but can't find the magic button in photoshop..
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Old 02-02-2003, 03:00 PM
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jeaniesa jeaniesa is offline
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Gonzo,

First, WELCOME to RetouchPRO!

If I understand your question correctly, I think that you want to do this:

1. If you're talking about a luminescence channel, I assume that is grayscale. So, make sure that the image you want to use for the mask is in grayscale mode.
2. Keep the grayscale image open along with the image you want to mask.
3. On the layer in the image that you want to mask, Load->Selection... Set the source document to your grayscale image and make sure that the channel is set to Gray. Click OK.
4. You should now see a selection based on your grayscale image. (Don't worry too much about the marching ant lines - the selection marching ants will only show areas that are above 50% gray and is not a good indication of what's actually selected when using a grayscale image for the selection.)
5. Click on the "Add layer mask" button at the bottom of your layers palette (second from the left). You should now have a linked mask that looks just like your grayscale image. (If you alt-click (PC) on the mask thumbnail, you'll see exactly what the mask looks like.)

Hope that I understood your question correctly and that my solution is at least close to what you're looking for.

Jeanie
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Old 02-02-2003, 03:03 PM
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DannyRaphael DannyRaphael is offline
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This may turn out to be a terminology thing, so bear with me. I'm not sure what you mean by a "linked mask."

Let's assume you're objective is to combine two Alpha channels, say, Alpha 1 and Alpha 2. These Alpha channels can be from whatever source... something you paint with black and white, a layer mask, a copy of one of the color channels -- whatever.

Duplicate Alpha 2 (drag the channel name over the "new channel" icon at the bottom of the channels palette), creating Alpha 3.

Then, SELECT > LOAD CHANNELS... (choose Alpha 1)
followed by SELECT > SAVE CHANNELS (from the dropdown that says 'New', click the arrow and choose Alpha 3)

Notice when you specify Alpha 3, the options Replace, Add, etc. become available. The resulting Alpha 3 will depending on the option selected.

Does this help? Keep asking if close, but no cigar. Now you've got two approaches to try. Not to fear. We'll get ya there - eventually.

~Danny~
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Old 02-02-2003, 03:09 PM
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jeaniesa jeaniesa is offline
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Danny, You mean SELECT > LOAD SELECTION and SELECT > SAVE SELECTION (rather than LOAD/SAVE CHANNELS), don't you?

Jeanie
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  #8  
Old 02-02-2003, 03:21 PM
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DannyRaphael DannyRaphael is offline
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Jeanie...

Thanks so much. Yes, load and save SELECTION... is what I meant.

Danny
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  #9  
Old 02-02-2003, 03:42 PM
gonzo gonzo is offline
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Danny and Jeanie, thanks a bunch!

Jeanie:

Yay! This does what I need! It seemed a somewhat illogical and strange way of going about it, but hey, it works! . As soon as I figured out that I could have several images open at once and cycle between them in the 'load selection' box (which I have tried before, but not taken note of), everything else fell into place.

It is not necessary to convert the image used as a mask into greyscale btw. I just tested it, and you can just copy the image into the alpha channel first (which is always greyscale, hence the luminescence chatter), and then load the alpha channel as a selection into the other image. Yay!

Oh, and now that I actually got my brain running (a rare instance, I have to say) it's dead obvious that I can just do this within the same image.. so: copy relevant layer into alpha channel, then load selection->alpha channel, and make a mask. THAT was the magic button I was looking for! I *knew* it had to be something truly simple because it's needed all the time.. I also knew I was gonna feel really stupid when finding the answer, so thanks for bearing with me.

I better write this down before I forget it again.. I seem to forget most things I learn in photoshop, and of course I can never find all the post its with hints and tips on either

Danny: I tried playing with the alpha channels like you instructed, and I hadn't tried subtracting and adding like that in alpha channels, so that was pretty cool.. not really what I was looking for, although I can't seem to wrap my mind around whether this could be used for the same purpose as well.. Sometimes I feel like I'm blind with all the options sitting staring me in the face and I can't figure out how to put them together.

Thank you both again for the help, very much appreciated.
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  #10  
Old 02-02-2003, 04:37 PM
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jeaniesa jeaniesa is offline
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Gonzo - glad I could help!! And yes, just copying the image to an alpha channel does make it a bit easier. I hadn't thought of that shortcut. Thanks!

Jeanie
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