In photoshop, brushes work by a black to white transparancy gradient. This means that everything that is black will be opaque, but white will be transparent. Greys become transparent in relation to their darkness – so a darker grey will be less transparent than a light grey.
In our image so far we can see that the background is a dull grey colour, which means it will not be fully transparent. To help remedy this, we will adjust the levels. Go to Image>Adjustments>Levels, or press ctrl+L
You can see how I’ve changed my settings below. If you’re lazy, you can move the right slider more to the left so that the background is completely white and you can skip straight to making it into a brush. However, doing this will lose some of the detail, and you will end up with a harsher, less natural looking cloud. So I recommend that you do it like I did, or close to that.
After doing so you will get something like this.
Step 4:
As you can see, the background is still a light grey, which will stop it from being fully transparent. To fix this, we will use the dodge tool to lighten the areas around the cloud, without affecting the actual ‘wisps’ and detail in the cloud.
Set the dodge tool to work on the ‘highlights’ (the lighter areas) of the image, or it will just wash out the black colours. It is also a good idea to set the opacity down to 20-40% so that you can get more detail with the dodge.
Now that the cloud is surrounded by white, we can finally make it into a brush. However, there is still a piece of cloud visible in the bottom right of the image. We want to choose just the central cloud to make into a brush, so we use the lasso tool to select it.
Step 5:
We then go to Edit>Create Brush to create the brush. Remember that in photoshop 7 and higher, the maximum brush size is 2500×2500px. In photoshop 7 and below it is 999px. If your image is a higher resolution than this, you will need to resize it.
Give your brush a clever or witty name like ‘Cloud Brush’ so that it can be organized later if you wish.
Now go on, and start using it! If you want it be more beautiful, make more brushes.
Original post: http://www.tutorialized.com/view/tutorial/Creating-A-Cloud-Brush/50973