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I have an image of smoke over a black background. If I set the blending mode of this layer to screen, the image's background is perfectly edited out, however if there isn't another layer below this, the screen mode does nothing. How can I make the background truly transparent, so it is just smoke on a transparent background? Colour Range selection is useless in this scenario, because smoke needs different levels of transparency throughout, and not just a clear cut selection. Thanks

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Thanks very much for this, very simple solution. –  user3373 Jan 11 '12 at 10:41
    
Awesome Dudes, this is what I've been struggling with sooo many times! There are still hero's. Thanks a million! Love figuring out new tricks. Have an awesome day! –  user3519 Jan 26 '12 at 11:08
    
Here is another technique that doesn't require any masking. Works best on black or white backgrounds: graphicdesign.stackexchange.com/questions/21685/… –  John Jul 8 at 14:17

4 Answers 4

up vote 18 down vote accepted

You don't see the transparency effect if there's nothing below the layer because there's nothing there for Photoshop to calculate (all these blend modes involve calculations based on the values of the corresponding pixels on each layer), so it just shows you the image.

In this particular case (as Farray pointed out while I was writing this!), you can pull an easy trick on Photoshop and make yourself a smoke-filled image with all the transparency intact. It's easy because you already have gray smoke on black, just like a channel.

Here's what you start with: I've taken a "smoke on black" image (Layer 1) and applied it in Screen mode over an arbitrary background (Layer 0).

Smoke on a background

Step 1. Hide all layers but the smoke.

Step 2. Switch to the Channels Palette and Ctrl-Click (Cmd-Click on Mac) on any of the channel thumbnails ("any" because in this case they're all the same).

Selection

What you've just done is load a selection based on the grayscale values in the channel you chose. Just like a mask, white is fully selected (opaque) and black is fully unselected (transparent), with the gray shades between.

Step 3. Create a new, blank layer, set your foreground color to white, and fill the selection. Hide all the other layers.

The new layer with transparency

Step 4. Deselect, turn on your original background, admire the result, and move on to greater things!

The end result

Farray's suggestion is very similar. Do steps 1 and 2 then use your selection to create a mask. The advantage of this approach is that you can then and "tweak" the mask in the Masks panel.

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Thanks! Fantastic answer, really helped me. –  Sam Jun 18 '11 at 8:11
    
Out of curiosity, is there a way to do this if the picture isn't grayscale? Maybe do the same, and then making a copy of the original layer, applying it with "Color" blending mode? –  Michael Jun 18 '11 at 10:13
    
There sure is; lots of them, in fact. Every channel (R, G, B and the composite RGB "channel") contains grayscale values, masks can be created from channels or combinations of channels, and so on. See the mini-tutorial on extracting clouds that luckycipher references below for a detailed exposition on one of the more effective and flexible ways. –  Alan Gilbertson Jun 18 '11 at 19:03

Welcome to Graphic Design. If the smoke doesn't have any colors in it, you could use the smoke image to create a layer mask on a white layer. This would change the blending to simple alpha channel instead of doing blending that is dependent on lower-layer pixels.

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Dead on. I expanded on the theme a bit. (Our answers overlapped!) –  Alan Gilbertson Jun 17 '11 at 18:37
    
@Alan your answer is much more eloquent (as is often the case ;) ) –  Farray Jun 17 '11 at 19:24
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Thank you for the kind words. :-) -- It's kind of fun doing these mini-tutorials on the fly, and once I've done one, the steps are locked in my head for the next time I'm doing a Photoshop teaching session. –  Alan Gilbertson Jun 17 '11 at 21:00
    
@Alan Agreed! It's become a simple and fun exercise to see how quickly and simply a workflow can be clearly explained. Today I got a bit lazy though. :o –  Farray Jun 17 '11 at 21:30

I had a similar question a while back trying to extract clouds this worked extremely well for me you might find this useful.

Effective way to cut out clouds in photoshop

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You're right. The technique here is really a special (simpler) case of that situation. –  Alan Gilbertson Jun 17 '11 at 21:02
    
Lol, I didn't even realize you were the same person that answered my question. I figured I would repost it here, it seemed relevant. Thanks again that really worked wonders. –  luclabs Jun 17 '11 at 21:34
    
You're entirely welcome. That's what this site is all about. –  Alan Gilbertson Jun 17 '11 at 22:34

Alan Gilbertson's answer worked well for a single-color image, but I needed to go through this process for a full-color image on a black background.

The PS action reviewed at http://www.howtogeek.com/59634/remove-backgrounds-automatically-with-a-free-photoshop-action/ (Author's download page here) ended up working beautifully.

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Please do not only link to a web site, suppose the link is broken, what would your answer help? Please explain what you mean in your answer ... –  Kurt Apr 17 '13 at 23:47
    
@Kurt Not sure if there's any extra information that could be added. Considering it's a PS Action, if the link is broken the whole answer would be invalid. I added, however, the Author's link too. –  Yisela Apr 18 '13 at 3:01

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