Photoshop tutorial: using Contrast Masking

Applying contrast masking
Open your image in Photoshop and make sure that your layers palette is visible. If it isn't, choose Window>Layers or hit F7. The first thing you're going to want to do is duplicate the background player of the image, by hitting Ctrl-J. You will now have two layers in your layers palette. Double-click Layer 1 and rename it Contrast Mask.

With the Contrast Mask layer selected (1) in your layers palette, set the blending mode for this layer to Overlay (2).You will notice that the image gains in excess of contrast and loses a lot of detail.

Then set the opacity to 80% (3). The opacity this layer can be changed later on in order to adjust the strength of the contrast mask. The higher the opacity, the stronger the contrast mask. For right now 80% will do.

Now Desaturate the contrast mask layer (4). Desaturate is found in the image menu under Adjustments. You may alternatively press Shift-Crtl-U. This will remove all color from the contrast mask layer making it now black and white. Under the same menu, choose Invert or press Ctrl I (5). This will invert the layer, and now your image will show much more detail than the original. What you did up to this point was to use an Overlay layer to apply contrast to the whole image, using a duplicated, saturated and inverted copy of the original image to apply the overlay to just the right spots. The problem is that your Contrast Mask layer is much too detailed for this contrast improvement to make the image look better. It's bringing out too much detail. It needs to be softened.

In the final step you will need to apply Gaussian Blur (6) to the Contrast Mask layer. Gaussian Blur is found under the filters menu. Adjust the Radius between 20 and 200. Keep an eye on the image preview to see which Radius works best for your image. For this example I used 37. Images with more resolution will need a higher Radius. Applying a blur applies the contrast mask effect to the general area instead of the exact detail of the image. The the trade-off is that you lose some detail gained in the previous steps, but the result is a more realistic photo. You may further adjust the Opacity of the contrast mask layer to tweak its strength.

Final Results
To directly compare the before and after, repeatedly disable then enable the Contrast Mask layer in your layers palette at look at the change in the resulting image. In the final image you'll notice that overall detail is increased, shadows are reduced and more balanced, in the overall brightness is better without blowing out the highlights of the waterfall. Contrast Masking can be a powerful tool for balancing the exposure across an image without destroying details. It's best that you experiment on multiple types of images in order to find out what works best in what situation.