There are so many different ways to increase an image's contrast in PhotoShop that it's hard to keep track of them all. I find that different artists adopt tricks that work for them, and just use one or two instead of the entire set. This approach to intensifying blacks is a friend of mine's super secret favorite trick. It's a good way to add punch to your shadows without altering the image significantly in any other way.
First, you pick an image to work on:
(Carly; "Collapsing from the Inside" cropped and cleaned-up)
The first thing to do is to perform a black/white conversion using channel mixer. Go to Layer->New Adjustment Layer -> Channel Mixer. Then check the "monochrome" box.
In this example, I chose mixer settings that gave me a desirable tone in the highlit parts of the image. But I thought that it'd be nice to have it a little bit darker.
The normal way I'd punch up the darkness would be to simply adjust the black point with a "Levels" adjustment layer. I.e.:
(messing with the black point)
This is HOW WE'RE NOT GOING TO DO IT. But let me mention a cool and worthwhile trick while we're on this topic. I couldn't grab a screenshot of it in action but, if you are dragging the black/white points in "Levels" you can hold down the ALT key and it will give you a visual map of the parts of the image that are going to clip to white or black at that setting. By "clip" I mean that they will lose all detail and turn either to maximum white or maximum black. Some photographers that I know use this as their sole guide in setting an image's contrast - they adjust it so that it's just clipping at the whites and the blacks - a full tonal range.
(black point and white point set to close to a full contrast range)
For the sake of having this image look good, I'll use "Levels" to set the white point and black point, but I won't push the blacks down very far.
Does it look a bit flat to you? Well, it does to me. And, since it's my photo, I'm going to deepen just the blacks using a black layer. Besides - that's the whole point of this tutorial!
First, we make a copy of the background.
(right click to make a copy of the background)
Then convert it to monochrome with Image->Adjustments->Desaturate (Control-shift-U). This doesn't really matter, but it helps me see which layer is which in the layers menu.
Now, adjust the levels in the black layer. You want to have it show dark where you'll be intensifying the shadows and white everywhere else. Since you're working on a layer, you can't use a layer adjustment, here. Just use Image->Adjustments->Levels
(this is where the shadows will dwell!)
Lastly, set the shadow layer to Blend Mode "Multiply" and adjust the transparency.
The effect will be subtle. You can see it, though, by clicking on and off the visibility of the shadow layer. And, of course, you can paint on the shadow layer if you want to. Another trick I've seen done with this kind of layer is to paint very faint textures into blown-out highlights.
You can see how the shadow on her spine looks sharper and more delineated. And her hair is "punchier" too - basically, the contrast of the image has been slightly stretched along the tonal scale, but only in spots instead of uniformly. Further adjustments to the black layer could be done with smudge tool or a mild gaussian blur.
Bellwether Farm , Morrisdale, Pennsylvania March 9, 2008