Contrast Masking

This is another technique borrowed from the darkroom.  The idea was to take the original color photograph and create an out-of-focus black & white negative.  The original photo and the B&W negative were sandwiched together and a print was made.  How does this improve our picture?  Everywhere the color photo was dark, the negative would be clear, allowing light to pass through easily, and everywhere the original was light, the negative would be dense, inhibiting light from passing through.  This would increase the exposure in the dark (shadow) areas of the original, and decrease the exposure of the light (highlight) areas of the original.  This technique allowed the photographer to increase the shadow detail without blowing out the highlights.  If we merely increased the exposure of the original, we could increase shadow detail, but at the expense of highlights (lighter colors, such as clouds, would be forced to white, and subtle detail in the clouds would be lost).

We can simulate this procedure in Photoshop.  Open a photo and create a duplicate layer (select Layer from the menu then Duplicate).  Remove the color from this layer (Image/Adjust/Desaturate), and create a negative image (Image/Adjust/Invert).  Blur the image a little (Filter/Blur/Gaussian Blur).  For an image resolution of 800X600 or 1024X768, try a radius of 5.  For larger images you will probably want to increase the radius a little.  The figure on the Right was used in this process.  Blurring softens the effect.  If you do not blur the image, you will produce a high contrast sharp image, which may look unnatural.  Too much, and you may see halos around the edges of objects.  Now, from the layers palette, choose overlay as the blending method.  If the effect seems a bit much, try reducing the opacity to 50%.  You might want to tweak the Levels, Saturation or other effects to fine tune the image.  The figures below show this effect, and I did not touch up the photos any further.  The image on the left is the original image, the center image was created with 100% opacity, and the image on the right was created with 50% opacity. If your resolution is low, the rightmost image may be placed below the other two.

You may notice that not only do we get more contrast, but the colors are more snappy.  The leaves in the shadows are coming into view and the clouds have not gone to white.  Quite the contrary, cloud detail has been enhanced.  Unfortunately, this technique may not produce pleasing results on all photos.  Color shifts, especially with flesh tones, may appear.

The steps are virtually identical in Corel Photo Paint.  First, open the image.  Then select Object/Duplicate, and Image/Adjust/Desaturate.  Now select Image/Transform/Invert to create a negative, and blur the image with Effects/Blur/Gaussian Blur, and choose a radius.  Next go to the Objects Docker, and choose Overlay as the blending method.  Except for some final touches, you are finished.