Layer masking (skies) the easy way

Ramseus

Have you been high today?
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Have you ever downloaded pictures off your camera only to find out that the sky's too bright? Photoshop to the rescue! Or maybe you just want to make the sky more dramatic, or you want to make the ground lighter, or some other masking that doesn't involve the sky. In this tutorial I'm gonna learn you how to mask quick and easy... most of the time at least. This requires photoshop. Basic photoshop knowledge should be good enough. If you're in need of more clearification, just say so.

First off, masking won't help you if you've completely blown out the sky and have sensor bloomage. Don't bother trying to fix that, that's a job for multiple exposures or *spit* grad ND's ( :p ) and is another subject.


Here's the picture I'm going to be using. Note the bright sky. Blech.





Step 1: beginning the mask

Duplicate the background (command + J, or ctr + J for windows lusers)
Now open up the convert to black and white dialog by hitting command + alt + shift + B (winders: ctr + alt + shift + B). It should look like this by default



What we're doing here is trying to make the sky as bright as possible and the ground as dark as possible by playing with the sliders. Pretty much all you ever need to do is just nuke red/yellow/green and make cyan/blue/magenta 300%



and the result is this (posterization not a result of compression, result of B+W conversion)





Step 2: cleaning up the mask

The goal is for the ground to be pure black, and the sky as white as possible. Making the ground black is more important than making the sky pure white.

So I have some garbage I need to get rid of - the guy and path need to be gone, obviously. Rectangular marquee, fill black, done.



My trees are now nice and dark. If your ground has some trickier light bits, you may want to burn it out. Just set the burn tool to shadows, and try to avoid burning the edges between ground and sky.

Your mask is now ready to be applied. You can, at this point, adjust the levels, or even the curves if you feel like it, to make sky whiter/ground blacker, but do try to avoid doing too much levels/curves adjusting of your mask as your edges will migrate a bit and you'll get haloing. You have been warned.



Step 3: Applying the mask

copypasta! Two ways to do this, the long way that I always use just because I tend to avoid going into the file menus for no particular reason, and the easy way which involves going into the file menus.

The long way: Select the canvas, copy. Create a levels or curves adjustment layer, this layer should now be selected, go into the channels tab of the adjustment layer (unless you've screwed up your UI the channels tab should be next to layers), make [layer name] mask visible, paste. Ground turns red. Make the layer mask channel invisible again, go back to the layers tab.



The easy way: make your mask (would be called Layer 1 unless you renamed it) invisible, create a levels or curves adjustment layer. Now up in the file menus click Image > Apply Image. For the layer, select your mask layer. I forget what the default blending is, if it's anything other than normal or multiply, just set it to normal.



Either way, the adjustment layer now has your mask applied. Adjust away.



Step 4: tweaking the mask

Ok, let's see now. With levels adjustment stronger than I should have done it just to exaggurate any issues with this mask looks like this.



Ok, so that looks... not too good. The problem here is that the trees near the sky are lighter than the trees lower down, my mask is masking the sky just fine, thank you. Thanks to leaves being slightly translucent, a bit of sensor bloom, and out of focus bits there are soft edges that are hard to deal with. Well, as far as this picture's concerned, all this can be solved just by putting a gaussian blur on the mask (click on the thumbnail of the layer mask to make changes to it).

Voila! Overprocessed sky is overprocessed and crap looking, but now everything looks OK.





Of course that's not going to work if the ground isn't so dark, if you did that with a light ground you'd get obvious haloing, so now I need a new exemplar. And here it is.



Using the same steps as before to create the mask, the result has less haloing than I expected. Again I overdid the adjustment to demonstrate where the mask fails.



Now if I blurred the mask if would be painful here, so screw that noise, I'm just going to take a soft 1000 pixel brush set to 24% flow and erase bits of the mask. The result is as such.





Any issues you end up with really depend on the picture and how heavily you darken the sky. This picture



turns into this without any fuss at all





this picture



turns into this with absolutely no effort put into it. Notice slight dark haloing on the castle. But, being easy to mask man made straight lines, I would just mask this by hand and avoid the very slight haloing all together.





This technique works well in most situations. Even when I am masking by hand I usually use this as a starting point, and then go in and make it better, but with trees there's no way I'm going to mask them by hand and this is really the only way to go. Just remember not to over do it, and this technique is, obviously, useless if you completely blow out the sky. If you have a nicely exposed sky and dark ground and want to brighten up the ground, do everything I just said, but before you apply the mask make sure to invert it.

Have fun. ;)
 

Ramseus

Have you been high today?
Joined
Jan 11, 2008
Messages
5,605
Location
Derpronto
^ try burning the whole sky evenly, going around trees and buildings and junk without burning them and burning the sky right up to them. Go ahead, I posted before and after pictures. If you can do that with the burn tool then you're clearly god :p Also this takes like a minute to do.

Where is that? Looks like Edinburgh, but I might be wrong....
Yeah. The tree pictures are from the trail near my house though.
 
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