Photoshop articles:
The right way to approach Adjustment Layer Masks
This tutorial is written in Photoshop CS4, but applies to all versions of Photoshop, and similarly to Photoshop Elements.
Introduction:
Many times, on the forums I frequent, I see evidence that new users of Photoshop are taking the indirect and counterintuitive route to their selective adjustments.
I hope to open your eyes to a much better approach to your layer masks.
The Common Approach:
Let's use this paddock photo as an example. It's lovely and serene, but the foreground lacks contrast.
It's possible to simply make a contrast adjustment as shown - that is, paying attention to the grass, and ignoring the sky ...
... and then painting on the layer mask to recover the sky ...
... giving a perfectly satisfactory result.
Shortcomings of the Common Approach:
Ok, so if the above technique gives good results, what's the problem?
There are two important, but overlooked, failings with the common approach.
1. The histogram is inaccurate. Take a look at the Levels histogram above. You can't identify the relevant data (ie the grass), because the histogram is describing the entire image.
2. You can't preview your adjustment accurately. In the above example, I couldn't tell when my grass looked "right" compared to the sky. I was just guessing. Only after I'd painted my mask could I evaluate if my adjustment looked credible, at which point I'd have to re-adjust the Levels if I'd erred.
The Better Way:
It is much better to make your selection before you make the adjustment. This way, the histogram is accurate and the preview is reliable.
This can be done in the same amount of time as the conventional method, and often more quickly.
Direct from Selection to Mask:
Begin by selecting the area of intended adjustment. I highly recommend the use of Quick Mask, because it mimics layer masking. (Of course, Photoshop offers more selection methods than you can poke a magic wand at!)
Choose your adjustment layer, and VOILA! Immediately, your selection becomes the mask on the adjustment layer.
Now, your histogram accurately represents the data within your selected area. This makes precise adjustments of Curves or Levels much easier.
Plus, you can watch your adjustment as you make it, and evaluate it in comparison with the rest of the image. This usually negates the need for repeated adjustments, and may speed up your workflow.
One more thing:
If you make your selections first, then you get to use the handy layer mask tricks.