In this tutorial we'll begin looking at color adjustments.

I must state here that there's a big difference between adjusting color for accuracy and enhancing it artificially to be something it's not. Any color correction will be suspected if the results fail to represent the color correctly or accurately.

That being said, I think it's good to know how easily color can be manipulated so that there is some healthy scepticism for some images that look too good to be true.

So, let's look at the simplest color correction method, which is an overall tonal correction of the whole image. We'll start with two images of the same cultivar. The top image is more accurate. At least to my eye, this truly shows the color I see in the garden. I understand this is subjective, but the color of the second image appears too yellow and washed out - partly this is the exposure and partly it's the color of the light at that time of day - you'll notice the foliage too has a yellow cast to the leaves.

Both together

Now, before we can begin we need to spend a moment talking about color theory on a computer monitor versus the color theory we were probably taught in art class. In art classes (and I have a BFA Degree in Painting, so I have suffered through a few) they taught us that the primary colors are Red, Yellow and Blue. Mix red and yellow to get orange, mix yellow and blue to get green, and mix red and blue to get violet; the secondary colors. These, red, yellow and blue, are are the primary colors for pigments. When we see a red rubber ball, we see the color red because the pigments in the covering on the ball absorb all the other colors and only reflect back to our eyes the color red. This is sometimes called the subtractive color wheel.

Computer monitors, however, use a completely different set of primary colors, as does your TV set. The primary colors of light are Red, Green and Blue; (thus RGB Monitors) the secondary colors are yellow, cyan and magenta. Look closely at your color TV and you'll see red, green and blue dots or stripes make up the image (this works only on CRT TV sets, not LCD sets). TVs and computer monitors create colors by mixing light. This is called the additive color wheel.

So, in this case, we are not mixing pigments, we are mixing light. In theory, if were were to mix red, yellow and blue pigments together we should get black (it never works that way, it's a dark, muddy brown). If we mix equal parts of red, green and blue light - we get white. Using the RGB Model, to make magenta, we mix red and blue light, to make make cyan we mix blue and green light and the one that throws lots of people, to make yellow, we mix red and green light!

Now, why is this important? We are going to try to correct the color in the lower image. To 'fix' it, we need to shift the overall color balance away from yellow - but what color do we add? You pick the color on the opposite side of the color wheel - so, since yellow is made up of red and green, the compliment is blue! So, to adjust this photo, we'll be adding blue light to the image.

(Here I should mention too; I never adjust an original photo. I open the file, do a Save As... and give it a new name and open that file to adjust. I then have a record of what the photo originally looked like.)

Photoshop and Photoshop Elements both have the tool we'll be using in this tutorial. Open the picture you wish to adjust and then go to the Image Menu - pick Adjustments - and then pick Variations. This dialog will appear:

adjustment 1
Looking at this dialog you see that there are 3 images labeled "Current Pick". At the top you see it compared to the original image. On the right side, you see it between a lighter and darker version. And, last, in the center of the RGB color wheel.

By default, the dialog opens with the midtones selected (see the upper right area) and midway between Fine and Course corrections. I like to set this slider more toward the Fine side than Photoshop sets by default, but I left it there so you can see the obvious shifts of color and brightness. As you move the slider toward Fine these changes will become more subtle.

To make an adjustment click once on the correction you desire. The "Current Pick" will now have that adjustment applied. Click additional times for additional corrections,

A couple of pointers when using this dialog. First, if you Cancel, nothing changes. If you get adjustment happy and feel you've gone way too far, clicking Original at the upper left brings the "Current Pick" back to the original so you can start again. In adjusting color, if you are working on the color wheel and add blue three times and feel twice was better - you can click once across the color wheel, in this case on yellow, and it will "back up" one correction.

In my image, I moved the adjustment slider to almost Fine and clicked twice on blue and once on Darker and then saved the image. To illustrate the change, the right side of the image below is the adjusted side and left is the original color and exposure.
adjusted image

Now, if you look at the color above you can see it's perhaps not perfect, but it is closer than the unadjusted image to the top photo on this page. Notice too how the foliage has been adjusted as well and that there are some noticeable blue tones now. The top image's foliage also has some small blue toned areas. Note that this adjustment isn't too dramatic - if you can tell by looking that an image has been adjusted, then you probably have over corrected.

One other part of the Variations Dialog should be explained here as well. Just beneath the Fine-Course slider is a checkbox labeled Clipping. Clipping is the shifting of pixel values to either the highest highlight value or the lowest shadow value. Clipped areas are either completely white or completely black and have no image detail. If you were to shift to adjusting shadows you might see this:
clipping example

Photoshop uses bright versions of the complimentary color (the one on the opposite side of the color wheel) to indicate that making this adjustment will drop these areas of the image off the range the monitor can show - you have reached zero value for that color in the area so indicated. While this isn't even always bad, if I don't say something folks might think that this adjustment is going to insert those wild bright colors - NO! If you uncheck the Clipping checkbox you can still see the results you will get, and as I said, they aren't always bad, but Photoshop does warn you when you clip colors.

Next tutorials we'll look at a number of other tools for adjusting color - some that act like a photographer's grab bag of tools and some that are, indeed, close to magic.

Tim Fehr - Eau Claire, WI

© 2007 by Tim Fehr - all rights reserved.