RGB and Color Channels in Photoshop Explained
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We know, or at least we'll willing to go along with the idea for the moment, that Photoshop doesn't see color. All it sees is black, white and gray. So how does it take those blacks, whites and grays and translate them into the colors we see on our screen? The answer is, it depends. Depends on what, you ask? It depends on which color mode Photoshop is using.
There's quite a few different color modes out there, but the two main ones are RGB and CMYK. A couple of others you may have heard of while working in Photoshop are Grayscale and Lab (pronounced "L-a-b", not "Lab"). These are all examples of color modes, and they determine how Photoshop translates its black and white information into color, with the exception of the "Grayscale" color mode, which doesn't use color at all. It's strickly a black and white mode, and is often used to quickly convert a color image into black and white.
Of these four that I've mentioned, the one we're going to be looking at here is the first one, RGB. The "CMYK" mode deals with printing and ink and is a whole other topic for another day. The "Grayscale" mode, as I mentioned, is strickly used for black and white images, and the "Lab" mode is beyond the understanding of most people on the planet, as well as a few people on other planets, although it is often used for professional image editing, but even then, most people who use it have no idea how it really works. Which leaves us with "RGB".
By far the most widely used color mode in the world of computers and technology is the "RGB" color mode. Photoshop uses it, other programs on your computer use it, your computer monitor uses it, so does your digital camera and scanner, your television, even the little screen on your cellphone or iPod uses it, as well as those handheld game systems like the Sony PSP or the Nintendo DS. If it's a device that either displays or captures images, or a software program that edits those images like Photoshop, it uses the "RGB" color mode. Sounds pretty important, doesn't it? And it certainly is. Yet for all it's widespread use and technological importance, all "RGB" stands for is the names of three colors - Red, Green and Blue.
RGB And Color Channels: The Colorful World Of Red, Green And Blue
So what's so special about these three colors, red, green and blue? Well, they just happen to be the primary colors of light. And what does that mean? It means that every color you and I can see is made up of some combination of red, green and blue. How do we get yellow? By mixing red and green. How do we get magenta? By mixing red and blue. What about orange? 100% red, 50% green. And these are just basic examples. Every single color that we can see is made up of some combination of these three colors. Sounds almost impossible, I know, but it's true.
When you mix fully saturated versions of all three colors together, you get pure white. When you remove all three colors completely, you get pure black. And when you mix equal amounts of all three colors at some percentage between 0 and 100%, you get a shade of gray.
Let's look at our photo of the bird again:
A very colorful image indeed, but where are all these colors coming from? Well, for starters, let's look at what the information along the top of Photoshop's document window is telling us:
As I've circled in red, Photoshop is telling us that this image is using the "RGB" color mode, which means that every color we're seeing in the photo is being made up of some combination of red, green and blue. If we want proof, all we need to do is hover the mouse over any part of the image and look in Photoshop's Info Palette.
I'm going to hover my mouse near the end of his beak, which is a bright red area:
Let's look at Photoshop's Info Palette to see what it's telling us about that spot in the image:
The part of the Info Palette we're interested in is the top left, as I've circled above, which shows us the RGB color values. One thing you need to understand here, and this is really a whole other topic on its own, but Photoshop doesn't list RGB color values as percentages, so we won't see values like "10% red, 40% green and 50% blue". Instead, RGB values are listed as numbers between 0 and 255, with 0 being absolutely no amount of that color in the image and 255 being the color at full strength. So if we look up at the area I've circled, we can see that the area I'm hovering over in the image is being made up of red at a value of 216 (a very high amount), green at 59 (a much smaller amount), and blue at only 1 (might as well be zero), which means there's practically no blue in that area and only a small amount of green. The vast majority of the color is coming from red, which makes sense since the bird's beak is clearly red.
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