How gray corresponds to color - Photoshop Tutorial

As we've already mentioned, we live in a color world, but to be effective with black-and-white imaging you have to understand how color translates into shades of gray. You're probably already familiar with the term RGB, an abbreviation for red, green, blue. Red, green, and blue are the primary colors of light. When you mix them together, you can create every other color. And you might be thinking, I remember from finger-painting class in grade school that the primary colors were different. That's because those were the primary colors of pigment. The primary colors of light, which is what we're concerned with as photographers, are red, green, and blue. And they differ from your finger paints because they mix together additively. As you mix the primary colors of pigment together, they get progressively darker, until you have a brown sludge. As you mix the primary colors of light together though, they get progressively brighter, until you have white. Take a look at this. I've got here red, green, and blue lights. These are three lights that have been filtered. This one has a red filter on it, this one a green, this one a blue, and they're casting these separate red, green, and blue patches on this wall. Now, the theory that I just said claims that we should be able to mix these together and get white, so I'm going to do that right now. I'm just going to tilt the lights until they combine. I am going to shift the red here over on top of the green and the blue here over on top of both of them, and sure enough, I'm getting white there in the middle. Now there are colors around the edges, and those are areas where the lights aren't perfectly overlapping. They're not perfectly registered. But I've done it; I've mixed these three primary colors of light together and gotten white. Now, you may be thinking, well it doesn't look perfectly white to me, and it's not--and there are few reasons for that. One, these filters that we're using they're not necessarily perfectly pure in their red, green, and blueness, same thing with the light bulbs. Also, we're shining on to a gray wall here. But still, I've mixed the primary colors together and I've gotten a white tone. By mixing the three lights in various combinations, I can create any other color, not just white. Getting accurate color in a photograph is not a simple thing because there are so many subtle shades and variations to every color. If you've ever seen a row of TVs at an appliance store, or tried to print a color image from your computer, you know that trying to precisely, accurately reproduce color can be difficult and frustrating. If something in an image is supposed to be a particular shade of red, we expect it to look that way, and getting an exact match from device to device, or from device to paper, can be tricky. Black and white is much more forgiving because there's no objective correlation between any particular color and a specific shade of gray. For example, consider this image. That blue sky there, if we were to convert this image to black and white, we could make that sky any shade of gray that we want. Here is the image with a grayscale conversion that renders the sky very white, and here's a conversion that renders the sky very dark. Both of these images look correct to our eyes, because again, black and white is an abstraction. The viewer will take care of interpreting the sky as a sky, no matter what shade of gray it is. But one of these skies might leave the viewer to interpret the sky in a way that has more emotional impact. This ability to choose how to render specific tones in an image affords you a huge degree of creative freedom and expression, and it's one of reasons that black and white can be a more expressive medium than color. In traditional film shooting, you use lens filters and film processing techniques to control how specific tones translate into gray. With digital photography, you control tonality when you convert your document from color into black and white. You can then exercise further control with additional image edits. Understanding tone in black and white is easy. This shade of gray is lighter than this shade of gray--that is, these two shades have different tones, but it's important to understand that individual colors also have a tone. So this shade of red is lighter than this one. It has a lighter tone. Now, none of this might come across as any kind of big earth-shaking insight, but as we move forward, both in shooting and post-production, you're going to see more situations where you need to be thinking about colors in terms of their tone. So it's important to start thinking now about the color world that you live in as a world of varying tones, not just varying hues. If all that sounds abstract, don't worry. We're going to explore this idea in much greater detail later.