Bair Art Edition's Tutorial on:
Adjusting Color & Exposure
In Adobe Photoshop
How to Use Layers In Photoshop: Opacity & Layer Masks
One of the most powerful functionalities in Photoshop is the ablilty to overlay images and objects on top of each other, and then change the overall opacity of those layers, or selectively change the opacity in certain areas of the layer.
Opacity is very straight forward. This option is found in the upper-right-hand corner of the Layers palette. It ranges from 0 - 100% opacity, and is very useful when working with adjusting color, sharpness, or any other adjustment.
The basic idea is to either copy the Background Layer and make any adjustment directly to it (color adjustments, sharpening, bluring, contrast, exposure, etc.) or make that alteration in an adjustment layer. Once you've made the adjusted layer (either using a duplicated layer or a true adjustment layer) then Go Overboard!! I mean it, allow yourself to go way sharp, way blurry, way magenta, way saturated, whatever you're doing, do it more than needed.
Now, simply go to the opacity of that layer, and you can adjust the opacity up or down, and thus you will essentially be increasing or decreasing that adjustment whenever you wish.
Let's talk about layer masks. A layer mask in Photoshop is applied to an individual layer, and is visible in the layers palette as an thumbnail which is linked to the layer's own thumbnail.
When a layer mask is thus applied, it's function is to tell the Photoshop application how much of that layer will be visible. If the layer mask does not define an area as being visible, then it becomes transparent.
As you see the mask thumbnail to the right of the layer thumbnail, you will notice that it is pure white, pure black, or a combination of the two.
Pure White = That portion of the layer is 100% Visible
Pure Black = That portion is 100% invisible.
Sometimes you may make portions of the mask a degree of gray. This means that it is not entirely visible or transparent. In this case the gray areas simply have a decreased opacity in that specific location, just like lowering the overall opacity, but now it is limited to that area.
Layer Masks are accessible in Layers/ Add Layer Mask/ Reveal All or Layers/ Add Layer Mask/ Hide All. Choosing "Reveal All" creates a white layer mask, and thus it reveals everything. Choosing "Hide All" creates a black layer mask, and thus hides everything by making it transparent.
You may also apply a mask faster by clickin on the Layer Mask icon in the bottom of the Layers Palette. Simply clicking on it creates a mask that reveals all. Option/Alt - clicking creates a black mask that hides all. (option for Macs, Alt for PC's).
If you have been using one of the selection tools, and a portion of the layer you are on is selected, as you create a layer mask the portion selected will be white on the mask (reveal all), and the portion not selected will be black (hide all).
You can actually paint black and white onto the layer mask (make sure it is the mask itself you are painting on), and it will act as though you are "erasing" and "painting" the layer off and on. Make sure your brush mode is set to "normal." You may paint with soft-edge brushes, and lowered opacity brushes; doing so will allow you to "feather-in" the edges and the layer itself.
These are the sections of this module: