RGB Gray - Curves Adjustment Layer

Preparation for Curves Adjustment Layer - Info Palette

Be sure to view the Info Palette while working with Curves. Click on info in the top palette on the upper right of the Photoshop interface. You can use the mouse in Eye Dropper Mode over the image to see what tonalities are in a precise area. For instance, if you place or position the mouse over an area that is completely black, you will notice that the Info Palette shows: R-0, G-0, B-0. We call this true black. If you are in the highlights, and the Info Palette reads: R-255, G-255, B-255, then this is true white.

Look at the Layers Palette

Make sure you are on the top most layer in your layers palette. This should be the Levels Adjustment Layer according to the workflow presented in these tutorials. Next, click on the New Adjustment Layer Icon at the bottom of the Layers Palette (looks like a ying / yang symbol).

Add a Curves Adjustment Layer

From the pop-up menu, click on Curves. Make sure your new Curves Adjustment Layer is the top most layer in your Layers Palette, and that it is highlighted.

The Curves Dialogue Box and features.

Let's look at the Curves Dialogue box and features. It starts out like this. The center of the line in the midtones range. The top right of the line is the highlights. The lower left is the shadows.

Understanding Clipping.

If you click on the Show Clipping Box in the lower right area, you can use this feature to find your darkest shadow tones and your lightest highlight tones. This is helpful if you wish to use the Black Point and White Point eye droppers.

Examples of altering midtones

Make a click on the diagonal line where you want to adjust tonal values. In this case, it is in the midtones. If you hold down the mouse and raise the point above the midline, then you just brightened or lightened the midtones in that image. If you lower the point below the midline, then you just darkened the midtones.

Examples of Increasing Contrast.

The "S" curve shows how much you increase contrast in an image. In this example, 3 clicks or points have been made on the curve. If you raise the highlights above the midline and drop the shadows below the midline, then you start to increase contrast. As you push these points further in opposite directs, you increase contrast even more. As a comparison to the darkroom, then of the example on the left as a #2 contrast filter, the example in the center as a #3 contrast filter, and the example on the right as a #4 contrast filter.

You may wish or need to do further correction and adjustments. In the next step on the website, it talks about using multiple Curves Adjustment Layers to help control contrast in an image. As a comparison to the darkroom, it is like printing with 2 contrast filters and burning & dodging.
*End Tutorial*