Take from : Photocritic.org
If you are reading this, you have probably heard people moaning about lack of contrast in one of your pictures. I am sorry about that, but — really — it is one of the most annoying things in the world. The medium of photography allows you to enhance the way you see the world, so you have an option of showing what you would like to show better. When the option is there - why not use it?
This is the picture we’ll be working with for now. I know it isn’t exactly the best picture in the world, but at least it is bland - it is nothing short of boring. Why? Well - mainly because nothing is the way it should be.
I believe that, in photography, black should be black. White should be white. In most cases, there is no real excuse for having almost-white and almost-black as the darkest and lightest point of your photograph (unless it is part of a photographic effect, in which case this all doesn’t apply.)
It’s worth noting that this article is aimed especially at beginners, who aren’t that clued up on Photoshop. If this doesn’t apply to you, you may just want to dive right into the adjustment layers instead!
You have probably seen the brightness and contrast tool: It is very useful, but clumsy to use. Instead, we will be using the Levels tool. You find this tool by pressing apple (or control, if you are using Windows) and L. Or you could go to Image - Adjustments - Levels.
This tool allows you to see a histogram of your image, before changing things so they fit into the colour space you are working in.
When you open the menu, you see a few things: Three eyedropper tools down in the bottom right. If you want to use the eyedroppers, pick the left one (shadow), and click a portion of the image that you feel should be absolute black (i.e. RGB value r0, g0, b0). Now, take the rightmost eyedropper tool (highlight), and click a portion of the image you think should be absolute white (i.e. r255, g255, b255). The levels tool will then adjust your image for you.
But… What is the middle tool, I hear you ask. That is the gray point tool - or white balance tool, if you will. If you have any portion in your image that is neutral gray (preferably a 18% (r50, b50, g50) gray, but any neutral gray will do), you can select this dropper, and the Levels tool will change the Red, Green and Blue channels separately, to allow you to fix a mis-measured white balance. It is quite effective, actually.
For this tutorial, however, I will be using fully manual corrections on the RGB channel. On the top of this dialog box, you can see RGB. This means that all changes you make will affect all the channels. You can, of course, adjust any of the channels separately, but if you feel you are ready for that, then what the hell are you reading this guide for?
Anyway. When you look at the histogram, you can see that in the left and right ends of the histogram, nothing is registered. This means that the picture I am using as an example actually does not have any “real” black or “real” white in it. In other words, it uses only a limited band of the spectrum. Which - if you ask me - is a waste.
So, our first change is to make sure that there is real black in our picture. Do this by sliding the left slider towards where the histogram starts registering properly. If you want more contrast, you can slide it past where the histogram starts, as I have done here. What happens then, is that some of the details in the dark areas of the image are lost, and it just becomes black. Which gives an illusion of high contrast. Which is what we are looking for.
The result of the above change is this:
We do the same to the highlights:
Move the right slider to the left, and see the result:
As you can tell, the contrast is now a lot better. But now the whole picture is a tad dark. You have probably already noticed the middle slider. You guessed it, this is your brightness slider (well, not strictly - matematically, it just weighs the brightness in the image differently, by ’stretching’ the histogram one way or another, or ‘gamma correction’, as you might know it. For all practical uses, however, look at it as the brightness slider)
Moving the brightness slider to the dark side makes the picture lighter, and vice-versa. It seems unlogical at first, but the explanation is the mathematical thing mentioned above.
I slide the brightness (gamma) from 1 to 1.16, and the result:
Now, I am almost happy, but there is still one problem; Because we have been playing with the layers, the colours look a bit unrealistic. So I go to the Hue / saturation control (ctrl + u, or have a look in the image -> adjustments menu), and pull the saturation down a few tads.
So here we go; Your classic before-and-after pictures:
Of course, the image still sucks, because the original photo wasn’t particularly good. It does, however, explain how the levels tool works.
Taking it to the next level
Now that you know the basics, it’s time to go further in-depth. Contrast is one of the most common mistakes photographers seem to make, so it makes sense to learn a little more. If you are interested in increasing contrast in post production, you’ll want Matt Greer’s website, especially his in-depth introduction to curves.
Good luck!
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