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Using Alpha channels in Photoshop?

freeny

freeny

macrumors 68020
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Sep 27, 2005
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Does anyone know how to use the alpha channels in Photoshop?

I use After Effects for motion graphics and use alpha channels from time to time to create transparencies and gradient transparencies, and it works wonderfully in the app.

For the life of me I cant figure out how to reproduce this in photoshop. I can use the alpha channel to create a selection which can then be used to crop out the piece of the image i need but this only works for objects that are completely opaque with hard edges.

How do I use the alpha channels to catch gradients like highlights on glass or the effects of smoke or fog etc?

I render images out of Maya which convieniently bakes the alpha channel into the image. Works great in AE but not so in Photoshop.

HELP!
 
A channel is just a greyscale image so it can preserve gradients and suchlike... you can take your mask/selection and either make a channel from it or work with the channel itself using a greyscale image through the channel mixer or working directly with a new channel created in the channels palette.
 
Thanks for the reply Blue. I know what an alpa channel is, I just dont know how to use/operate it within Photoshop. Do you know of any tutorials or diagrams that would walk me through the steps?

It seems odd to me that AE and Photoshop are both Adobe products but use different approaches to using alphas.

In AE, you would just place your alpha channel on the layer above the object you wish to add transparencies to, set the layer to alpha and presto!
 
freeny said:
In AE, you would just place your alpha channel on the layer above the object you wish to add transparencies to, set the layer to alpha and presto!
Click to expand...

Which is a mask which can also be a channel which can also be a selection... ;)

It's a matter of terminology; it sounds like what you want to do is make a layer mask. And save it to an alpha channel.

Search for 'creating and editing layer masks' within Photoshop Help. It's a good place to start... if you want to preserve transparency, remove the background layer from your artwork.

Most of this can be done within the Layers palette...

Also read: About Masks, Quick Mask, Unlinking Layers and Masks...
 
I'm not sure exactly what you are asking but here goes.

When you open up an image in photoshop, it will mostly be either RBG(web/screen) or CMYK(print). In either case, each color is it's own "alpha channel"( Red, Green or Blue, etc) If you are looking to isolate certain parts of an image, you can either go into each color channel and see which one best shows what you are looking for and then just simply, make a copy of that color channel which will now become it's own channel which you should name (i.e. Highlights). At this point you can do what you like with that channel. The other option is just creating a new channel and paint or add a graidient of your choose. Ofcourse this is alot more to this but that's the jist. I hope some of this was helpful.

Check this out... channels.... might help.

If not you can always sign up for the online tutorial at Lynda.com . I highly recommend it.


~e
 
Thanks for the help Blue but I guess I'm gonna need someone to walk me through this. The Help section wasnt very helpfull, it only spoke of black and white, transparent or opaque, no grey or semi-transparent. It basicly told me to do what I already knew.
 
thanks eclipse525, I think that will help. Just from looking at the steps I start to wonder why Adobe doesnt implament the alpha functions of AE into Photoshop. This would save lots of time and steps.

eclipse525 said:
Check this out... channels.... might help.

If not you can always sign up for the online tutorial at Lynda.com . I highly recommend it.
Click to expand...

Okay, this is starting to make some sense. Why you cant duplicate the rgb layer is beyond me. this would save soooo much time as I said before. Having to do this one channel at a time seems a bit retarded when another Adobe product has already implimented it. ?????
 
freeny said:
Does anyone know how to use the alpha channels in Photoshop?

I use After Effects for motion graphics and use alpha channels from time to time to create transparencies and gradient transparencies, and it works wonderfully in the app.

For the life of me I cant figure out how to reproduce this in photoshop. I can use the alpha channel to create a selection which can then be used to crop out the piece of the image i need but this only works for objects that are completely opaque with hard edges.

How do I use the alpha channels to catch gradients like highlights on glass or the effects of smoke or fog etc?

I render images out of Maya which convieniently bakes the alpha channel into the image. Works great in AE but not so in Photoshop.

HELP!
Click to expand...


If you save the Maya render as a .tif instead of an .iff you will get an alpha channel for Photoshop. Not sure if that's what you are after.
 
freeny said:
Okay, this is starting to make some sense. Why you cant duplicate the rgb layer is beyond me. this would save soooo much time as I said before. Having to do this one channel at a time seems a bit retarded when another Adobe product has already implimented it. ?????
Click to expand...

You can duplicate the RGB layer. Just go into your main Layers palette. Select the image and copy. Then go back to the Channels palette and create a new channel. Then paste into that New Channel and WahLaa!

~e
 
ATD said:
If you save the Maya render as a .tif instead of an .iff you will get an alpha channel for Photoshop. Not sure if that's what you are after.
Click to expand...
I already do this for importing into After Effects and it works beautifully. Not so for Photoshop.

eclipse525 said:
You can duplicate the RGB layer. Just go into your main Layers palette. Select the image and copy. Then go back to the Channels palette and create a new channel. Then paste into that New Channel and WahLaa!

~e
Click to expand...
Nice trick eclipse. It almost works.
 
freeny said:
I already do this for importing into After Effects and it works beautifully. Not so for Photoshop.


Nice trick eclipse. It almost works.
Click to expand...



Still not sure what you are after but an alpha in Photoshop and masks are pretty much the same thing. The alpha in Photoshop will not do anything to a layer unless you make it a mask. You can copy the alpha then paste it into the mask of that layer. Is that helping?
 
Odd, if you are rendering your images with an alpha channel, it should show up in your channel palette within PS... probably named "Alpha 1", or something like that.

If so, you should be able to load (or copy/paste) this channel into a layer mask (invert as needed).

I do this but using targa files. I don't see why a tiff would be any different. You might be able to render/export directly to PSD format to save some time.
 
Orlando Furioso said:
Odd, if you are rendering your images with an alpha channel, it should show up in your channel palette within PS... probably named "Alpha 1", or something like that.

If so, you should be able to load (or copy/paste) this channel into a layer mask (invert as needed).

I do this but using targa files. I don't see why a tiff would be any different. You might be able to render/export directly to PSD format to save some time.
Click to expand...
All the alpha channels are there, I just coldnt figure out how to use them.

Thanks all for your help:)
 
Lynda.com

Hi,

If it is within your ability you might want to check out www.lynda.com. For $25 a month you can get qt movie tutorials for almost everything. I have been using them for about a year and I highly recommend it.

Tony
 
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