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I've had to use clouds in projects on more than one occasion, and I'd like to find a way to extract (select only) the clouds.

There are a lot of good brushes for this type of thing but often times they're too small, If I could figure out the process used to make something like this I would be able to make my own from stock images.

The brushes below are a good example of what I'm trying to achieve. They're cut very nicely and will look clean on any background

http://browse.deviantart.com/?qh=&section=&q=clouds+brush#/dkep1o

Any help is much appreciated.

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Here are some high quality cloud brushes (they are included in the pack): adonihs.deviantart.com/art/My-Brush-Pack-118954791 I've used these myself, and they give some great results! –  Johannes May 14 '11 at 20:05

2 Answers 2

up vote 12 down vote accepted

To answer the question asked:

This is easiest to do if you start with images that have fairly good, clean cloud edges against a plain blue (or orange, or whatever) sky. Photoshop lets you get from any given Point A to some other Point B in a bunch of different ways, so here's a technique that will work in just about any version.

Photoshop creates brushes from grayscale values. Black parts of an image or selection become fully opaque in the new brush, white parts are fully transparent, and shades of gray translate to different levels of opacity, just like they do in a mask or an alpha channel, our clouds have to be BLACK, but so that we can see what we're doing we're going to keep them white until the very last step.

Step 1. Pick a good image with clear cloud shapes and good contrast as a starting point. Overall image quality isn't important, just the clouds. One like this will work well, but feel free to experiment!:

Clouds (Copyright 2002 Alan Gilbertson)

Step 2. In the Channels palette, find the channel that has the best detail and highest contrast between the cloud and its background. (Hint: The red channel for daytime skies, blue channel for orange sunrise/sunset.)

Pick the best contrast channel.

Step 3. Now we're going to lighten the highlights, darken the sky and make a new document all in one shot, using a command most users have never touched and never wanted to get anywhere near: Calculations. (Was that a momentary frisson of terror I detected from the gallery? -- Have no fear, my friends! No images were harmed in the making of this tutorial.) Select Image > Calculations.

The Calculations dialog

In the dialog, select "New Document" in the "Result" drop-down (way down at the bottom), as shown.

3b. We're going to play the Red channel against itself, and the default blend mode of multiply may not give you the best results. This is a great place to experiment with different modes (and find out that Calculations, far from being intimidating, is actually way cool). With this example image it worked out that Hard Light, with an Opacity of about 70% gave a good result, but every image is different. Click OK.

Hard Light at 69%

Now we have a new document with only one channel, called "Alpha 1". We need to make the parts of the image that we don't want to be in the new brush completely black, without messing up the nice texture in the cloud:

A new document with only one channel

  1. Press Ctrl-L or Cmd-L to bring up the Levels dialog. In this case we already have good blacks, but the whites benefit from a minor tweak to the highlight slider, bringing out a little more texture in the clouds.

Levels adjustment

  1. Clean up any unwanted gray bits (the bottom left, in our example) using the Burn tool. Set the Range to Shadows and Exposure to about 25%. You want to darken the shadows to black, but without destroying the fluffy cloud edges, so take it gradually!

Unwanted areas are burned to total black with the Burn tool

  1. Invert the image (Ctrl/Cmd-I) and check the white areas to be sure they are entirely white. Use the Dodge tool set to "Range: Highlights" and "Exposure: 50%" to clean up any stray gray areas.

  2. Choose Edit > Define Brush Preset, give your brush a name, click OK and you're done!

Name your new brush preset.

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This is exactly what I needed! Youre absolutely right, I've never touched calculations, and I definately I wouldn't have figured this out myself. Thanks a lot! –  luclabs May 14 '11 at 22:05
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Generalising, don't cut something out manually if there's a way of deriving what you need from image processing. –  e100 May 17 '11 at 12:39
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Ain't dat da trufe! I was horrified once when I discovered a colleague extracting part of an image from its background with the regular eraser tool in Photoshop CS3. With a mouse. I kid you not. He had over 10 years of Photoshop experience and had never thought of doing it any other way... Yikes. –  Alan Gilbertson May 17 '11 at 18:11
    
The book 'Photoshop Channel Chops' (I think) used to the bible on this. Looks like it's out of print. –  e100 May 26 '11 at 13:09
    
This really is a great answer. –  e100 May 26 '11 at 18:23

you can create your own clouds in Photoshop all you have to do is follow one of these tutorial and make your own clouds and save them as a pattern or brush for future use.

  1. http://www.n-sane.net/effects/fluffy-realistic-clouds/index.php
  2. http://www.psawesome.com/tutorials/quick-tutorial-create-white-clouds-on-a-sunny-sky
  3. http://www.hacktweaks.com/2010/10/create-realistic-clouds-using-any-version-of-photoshop.html

now if you need to crop the only clouds

cntrl+click on the cloud layer from layer palate and crop it than save it.

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Thanks buddy, not exactly what I was looking for, but I'll check it out –  luclabs May 14 '11 at 22:13

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