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Photoshop CS5 for Photographers provides comprehensive Photoshop training targeting the needs of photographers. In this course, author Chris Orwig demonstrates the fundamental skills used to enhance digital photos, including managing and correcting color, sharpening, making selections and adjustments, retouching, and printing from Photoshop. In addition to teaching the techniques that enable photographers to refine and publish their photos, the course includes live-action segments that encourage thinking photographically and shooting with Photoshop’s capabilities in mind. Exercise files are included with the course.
For anyone who is interested in photography, or for that matter, for anyone who is interested in creating compelling photographs, well, it's worthwhile to take a few minutes to dig into the topic of the digital image. What exactly is a digital image and how is it made? How is it created? What are the different building blocks that come together to give us what looks like continuous tone photographic quality images? Well, in order to understand the digital image, one of things that we can do is jump back to the time when people when people were trying to come up with a way to create color photographs.
Now, much of color photography is attributed to James Clerk Maxwell. He came up with this idea that he photographed the same image differently. Then he projected these images with red or green or blue colors or filters. What happened was the combination of these three different colors created what look like a color photograph. Now, if someone said that to me today, said, "hey, Chris, I am going to project three different filters, red, green and blue.
I am going to make a color photograph." I would say, "You're crazy. There is no way that's possible." But it's true. This really is the basis for all that we do inside of Photoshop in regards to working with red, green and blue images in this RGB color space. So, really when we are working on our photographs, we are not necessarily working on a color photograph. Rather we are working on the photograph that's a grayscale image with different colors shown through it. The combination of these different colors give us a full-color photograph.
Well, let me explain. Let's dig a little bit deeper. We work in this space, which is the RGB color space. Here in RGB we create colorm hue and tone based on different variables. For example, this color orange here. For the sake of an argument, let's say this was created with a mixture of 240 red, 12 green and 15 blue. It's a combination of these different values which give this pixel its particular color. Again, let's dig a little bit deeper.
Well, the term "pixel" is a concatenation of two words, picture and element. We know that if were to zoom in on a small area of a photograph like the eye here, what we would see would be these little teeny picture elements, these little pixels. It's the combination of all of these little pixels that together give us something that looks like a continuous-tone photograph. Well, how do we actually get these pixels and where do these pixels come from? Well, if were to focus in on say one pixel, that one pixel is based on a bit.
A bit is a binary digit. You may be thinking, okay, this is kind of weird. What is a binary digit? Well a binary digit really is something that you can consider as either on or off. There are two options there. Now, if we add up these options, we can come up with more information. 8 bits is 1 byte, 1024 bytes is 1 KB, 1024 KB is 1 MB, so on and so forth. Well, how then does this relate to us in regards to working in Photoshop? Well, if we have a one-bit pixel, we either have black or white. That's it.
If we have a two-bit pixel, well, then we have few more options. White, gray, dark gray or black. If we go all the way to an 8-bit pixel, we actually have 256 levels of information. The interesting thing is is that when we go to this red, green and blue space, what we have is we have 256 levels of red, times green, times blue, which essentially gives us 16 million color possibilities.
In other words, if we have enough information, if we have eight bits per channel, we then have all of these different variables, all of these different possibilities and options, which ultimately give us the ability to work on images and to create images that have what looks like continuous tone. Well, why then talk about bit depth? Well, bit depth, this whole idea of a grayscale, is going to show up all over the place in Photoshop. In other words, we are going to see it in levels. For example, 0 to 255. Well, 256 levels, right? We can start to understand these levels.
We can understand them based on different channels or based on different controls. We'll see this also in Curves, again, 256 levels here, or we'll see it in places like our Channels panel. Here we have the red channel, the green channel and the blue channel. Here, we see kind of the mystery behind these images ,that it's really a grayscale image with red light being shown through it. Then the combination of the red, and then the green, and the blue, just like James Clerk Maxwell did, then gives us the composite full color photograph, which again has this nice, even and continuous tone.
Well, then if I have to distill this, why learn about bit depth? Well ultimately, what bit depth helps us to do is take images that might look like this, and turn them into something that will look like this. In other words, understanding a bit about bit depth equals better images.
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