Photo Editing
Color Balance

Getting the color right can be the most difficult part of photo editing but a little knowledge of how the colors are made will make this much easier. On the right we have a color wheel' to help illustrate the concepts that you need to grasp.

All colors are made from three primary colors - red, blue and green. Forget what you learned in Art at school we are now dealing with light not pigments.

Where the three colors overlap in the middle of the color wheel we get a neutral gray (somewhere between black and white depending on the intensity of the colors). I have faked it here slightly for the purpose of illustration.

Where two of the colors overlap they form other colors known as 'subtractive primary colors Another way of looking at it is that if you remove one color from the middle of the wheel you will get a new color For example, if you remove red from gray you will be left with a mixture of blue and green, this color is called 'cyan'. If you remove or subtract green from neutral gray you are left with a mixture of red and blue known as 'magenta'. Red and green combine to make the third 'subtractive primary color - yellow. Knowledge of these six colors and how they relate to each other will enable you to correct any color cast in a picture.

Now let's look at the tools available in Photoshop to help you with color correction. First and most primitive there is auto color (auto levels is a combination of auto color and auto contrast). Auto color can be found on the 'image->adjustments' menu. It works on a well established principle that has been used in the photo finishing industry for many years. Observation of the photographs that the 'man in the street' takes led to the conclusion that in 95% of all photos taken the colors in the picture, when integrated or added together, balance each other out and integrate to neutral gray

The large machines that were used to print your photos from negatives all worked on the same principle, they put a diffuser in front of your negative and adjusted the color head to print gray As I said this worked well enough in 95% of all photos sent to the labs and it can indeed work well in Photoshop. If your composition 'fits the mould', and an awful lot of them do, then 'auto color will work very well.

If, on the other hand, you have a predominance of one side of the color spectrum in your picture then 'auto color will introduce a color cast of the opposite color When this happens, and the photo looks worse than it did before, hit the 'undo' button and move on to the next tool.

Color Balance

Selecting the color balance' choice on the 'image->adjustments' menu brings up the window below.

This is by far the best window for adjusting the color of photographs. Unlike some of the other windows for adjusting color, like the 'hue saturation' window, this one is quite subtle in it's effect and, unlike the 'variations' window, you can preview the effect on the actual picture itself.

First let's talk about the 'tone balance' box at the bottom. You'll find that most of the time you can leave the radio button set to 'mid-tones' for best results, unless you are dealing with very difficult lighting. Keep the 'preserve luminosity' ticked to stop the picture getting darker or lighter as you change the color

Now let's move on to the color balance' box. Here you can see the color wheel in action. The three sliders show the opposing colors at each end. Look carefully at your picture, decide which color you need to decrease and adjust the appropriate slide. The hard part is deciding which color you need to get rid of, I have a lot of trouble deciding between cyan and green, also between green and yellow. Try different sliders to see whether the color cast is disappearing and to see whether you are introducing a new, different color cast. If too much of the new color is appearing before you have got rid of the color cast you are trying to get rid of, then you have got the wrong color I realize that the last sentence may be a bit hard to follow so here's an illustration.

The picture above is too red right? The opposite of red is cyan so let's dial in some cyan.	Now the picture is turning blue even though it still looks a little too red.	The first picture wasn't too red it was too magenta. We needed to add green not cyan.

You might argue that the last picture is too yellow though, as it was taken in the late afternoon sun, that is the way I think it should be. There are no 'right' and 'wrong' answers to color balancing, in the end, it's what you like. You can drive yourself crazy trying to get the color right, especially on an indoor picture under mixed lighting or a picture taken on a cloudy day that you would like to brighten up, it's just good to be able to 'fine tune' the color in your photographs.

I mentioned the 'variations' window that you will find in Photoshop at the bottom of the adjustments menu. This is quite good for complete beginners and for pictures that are a long way out of balance but I find that it is quite difficult to see what the effect is going to look like from the preview window so I don't use it very often.

The 'hue & saturation' window that I also mentioned earlier is more for creating color effects and one slider covers the whole color spectrum. The adjustment is far too coarse for the small amounts of color change we need.

Photoshop Tutorial	Description	Level
Size	Scaling your files.
Contrast	Balancing those pixels.
Colour	Dealing with colour casts.
Levels	A short video showing how to use the levels adjustment to control contrast.
Processing RAW Files	An introduction to Adobe Camera Raw.
Processing RAW Files using HSL	Advanced use of ACR.
Sharpening	Using the unsharp mask.
Using the Quick Mask	Masking parts of your picture to edit certain areas.
Adjustment Layer Masks	How to build accurate layer masks.
Straightening Horizons	A must for landscape and building photographers.
Replacing Boring Skies	Using layers in Photoshop.
Videos on Compositing	Video tutorials on using layers.
Using the Channel Mixer	How to make a better job of changing images from colour to black & white.
Using Curves on Adjustment Layers	laying with contrast and tones to give a more dramatic effect.
High Dynamic Range	How to shoot and process HDR pictures with Photomatix Pro software.