From the course: Photoshop CC 2017 One-on-One: Advanced

Three ways to convert to grayscale - Photoshop Tutorial

From the course: Photoshop CC 2017 One-on-One: Advanced

Start my 1-month free trial

Three ways to convert to grayscale

“

- [Narrator] Before we take a look at how you can mix your own custom black and white images, let's take a look at black and white at its most basic, which is grayscale. And a grayscale image is one that contains just a single channel of data. And there's three ways to make them, as we're about to see. So, the first step is to switch over to the channels panel, which you can get, either by going up to the window menu and choosing the channels command, or by clicking the tab right next to layers. And then, notice that this is an RGB image, meaning that it's mixed from red, green and blue data. And each one of these channels is a single grayscale image. So, here we've got the red channel, which is quite bright as you can see. I'm going to zoom in here though, so we can things a little more up close and personal. So, this is a red channel, very bright. This is a green channel, which is going to appear darker. And the reason it's appearing darker is because we're looking at a portrait shot. So, at any time you're looking at red-blooded human beings, doesn't matter race, gender, any of that stuff. You're going to see the people darken up from the red channel, where folks are always the brightest, to the green channel. And then darker still, in the blue channel. And things in this image in particular, darken up significantly in the blue channel to the point that we have what's known as posterization, which is to say very abrupt transitions in luminance levels. So, notice I'll go ahead and zoom in on the girl's face even more closely. Notice how we have this very brittle data down here in a shadow detail and we have this posterization right here along the side of her forehead. Which is why the blue channel typically plays the smallest part when you're mixing black and white images inside Photoshop. All right, I'm going to go ahead and zoom out here, so that we can see the entire family. And I'll go ahead and switch back to the RGB composite. But here's something you should know. The blue channel, the green channel and the red channel, each one of them, in a standard RGB image, contains 256 different luminance levels from black to white. Which is why your standard every day average RGB image contains 256, times 256, times 256 colors, or at least as many as. Which is about 16.8 million possible colors in all. All right, so let's see those three ways to convert this image to grayscale. I'm going to start things off here by going up to the image menu and choosing the duplicate command. And I'll call this first duplicate luminance only, let's say. And then I'll click okay. And now I'll create another duplicate by going to the image menu and choosing the duplicate command. And I'll call this one, let's say, red channel. And then I'll click okay. All right, now I'll go back to the original image right there. And I'll go up to the window menu, choose a range, and then choose 3-up vertical, so that we can see these three different variations on the image. And I'm going to zoom in on this guy right here, pretty tight. And, then I'm going to go up to the window menu, choose a range and choose match all, in order to make all the images match on screen. So that we can track the same detail. All right, now the first way to make a grayscale image, is to merely go up to the image menu, choose mode, and choose grayscale. At which point, you're going to get an alert message telling you, are you sure you don't want to use a black and white adjustment layer, which we are going to see, and it is a terrific feature, but for now, I'm just going to go ahead and discard the color information. And that's going to leave us with a single channel called gray, here inside the channels panel, that contains 256 luminance levels and nothing more. All right, now I'm going to move over to this image that's called red channel. And I'll go ahead and click on the green channel to view it by itself. And notice how very similar the green channel is to the grayscale composite that Photoshop mixes automatically. They aren't identical, but you would swear from what you're seeing here, that they are. Whereas, the blue channel is obviously much darker, suffers from all this posterization and the red channel is much brighter. And because it's the most different channel that's in good shape, I'm going to keep it by clicking on it right here and then returning to the image menu, choosing mode and then choosing grayscale. And notice this time the alert message reads, discard other channels, as opposed to discarding the color. And that's because as soon as I click okay, Photoshop goes ahead and throws away the green and blue channels, and leaves me with just a grayscale image made from the red channel exclusively. And that's a function of selecting that channel there in the channels panel and choosing the grayscale command. All right, there's one more way to work, and that's to extract the luminance only information. And you do that by going to the image menu choosing mode and then instead of choosing grayscale, drop down here to lab color. And that goes ahead and converts the color information from RGB to lab, which includes this lightness channel right here, as well as two other channels called A and B. Now they don't stand for anything. They're just two opposing color axes. And to get a sense for how they work, I'll go ahead and turn on the blue channel. So, you can see quite obviously this is the yellow to blue information right here. Which is more commonly known as temperature. And it is, in fact, analogous to the temperature information that you can tap into using camera raw. Whereas, if I turn off the B channel, and turn on A, this is our tint information right here. Now, folks commonly say this is the range of colors between magenta and green, but if I were to scroll up here, to this green background, you can see that this is not green at all. So, it's generally better to think of it as being the pink to turquoise data. But in any event, A and B mixed together forms all of the color information. But, let's say I just want the lightness, then I would go ahead and turn off A and B there and with just the lightness channel selected, I'll go up to the image menu, choose mode, and then choose grayscale. At which point Photoshop will once again ask if you want to discard the other channels. And then if you click okay, then you're left with just one channel of information, that's based on that lightness channel. All right, now I'll just go ahead and press the tab key to hide all the panels and I'll scroll over so that we can see this little girl here. And those are the three ways you can mix entirely different, single channel, grayscale images from a full color photograph here inside Photoshop.

Contents