Photo editing falls into two categories: Adjustments, which affect the whole photograph (much like our introduction to contrast, using the levels tool, from yesterday), and spot editing, which affects a smaller part of an image. Any photo editing you do with brushes, selection tools etc would be a spot edit.
While spot editing can be useful, it’s adjustment editing which is the big advantage for most photographers. Exposure a little bit off? Fix it in Photoshop. White balance problem? Photoshop. Want your picture in black and white? Photos… you get the idea.
What most photographers don’t know, however, is that you can do a wide array of adjustment editing experiments without even touching the original photograph. You can do this by adding so-called adjustment layers. This is a layer added on a photo which affects all the layers underneath. The upside of using this technique is that you can turn adjustments layers on and off, you can change their order, and their parameters. The main effect is that it is much easier to experiment with your photos, in the hunt for finding a combination of adjustments that makes your photo perfect.
My old friend Matt Greer explains:
The benefit to using adjustment layers is that no edit is permanent until you flatten the image. You can even save the image with all of its adjustment layers as a Photoshop Document (.psd), and when you reopen it, all the changes you made to the adjustment layers will still be there for you to change back, remove, or alter.
If you were to, for example, edit curves without layers, then go on to change saturation, crop the image, then add vignetting, the only way to go back and change what you did to the curves would be to go back in the history, to when you changed the curve (thus losing all work done since), or start the image editing from scratch.
With adjustment layers, however, so long as that adjustment layer is still there, you can go back and alter the adjustment at any point in the editing process. It is a lossless editing process, and very handy. Sometimes one edit will effect the way another edit appears, so the first edit may need to be tweaked. This makes editing far more efficient and accurate!
The kid obviously knows what he is talking about. So — instead of trying my damndest to explain the arcane arts of adjustment layers, I’ll lett Matt do the talking, in his fabulous blog article titled Standard Photoshop Adjustment Layers.
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