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The elusive alpha channel remains one of the most misunderstood yet powerful tools in Photoshop. Alpha channels are collections of luminance data that control the transparency of an image, and they inform just about every aspect of Photoshop. As he builds transitional blended layers, fashions a depth map, makes edge adjustments, and takes on extreme channel mixing, Omni Award-winning expert Deke McClelland teaches Photoshop users that where there's a will, there's a way. Photoshop CS3 Channels and Masks: Advanced Techniques covers mapping texture on an image, turning flesh into stone, using vector masks, working with all different channels, creating a rustic edge effect, and much more. Exercise files accompany the tutorials.
Download Deke's customized keyboard layouts for Channels and Masks from the Exercise Files tab."
Now that you have a sense of how you can use the Channel Mixer function in order to convert an RGB image to Black and White, let's use that exact same function to fabricate our own custom Black and White version of the image, something that pops a little better, something with a little more sizzle. Now if you are just joining me you can catch right up by opening this image right here, it's called the Industry standard gray.psd. It's found inside of the 13 Channel Mix folder. It's that same image from photographer Alexander Heathman. And what we've done here is we've used the Channel Mixture adjustment layer in order to duplicate the effects of an industry standard RGB to Grayscale conversion.
Now bear in mind we haven't gotten rid of any color channels inside of this image. So it's still really truly an RGB image, as witnessed by the Channels palette. I am going to go ahead and bring my Channels palette up on-screen, and you can see that there is the RGB composite which comprises a Red channel, a Green channel, and a Blue channel. Now notice that every single one of these channels is identical to the others, therefore we have a no-saturation image. So we've robbed the image of all color saturation, thanks to the fact that Red, Green, and Blue have no variation between them.
Now the RGB composite does look a little different than the independent Red, Green, and Blue channels for the very simple reason that we have color management at work inside of Photoshop. Let's switch back to the Layers palette here. And you can see that we've got a B&W adjustment layer, that's the Channel Mixer adjustment layer. And if we were to turn it off, there is our original RGB image still intact so we have still got the colors to work with if we want to. And that's a great thing, because now we can modify our Channel Mixer settings in order to get a better black and white mix.
Now before we do I am going to go ahead and turn that adjustment layer back on. Before you start mixing I recommend that you bring up the Histogram palette. Now if you don't see the Histogram palette right here, if you don't see a tab for the Histogram palette, then go up to the Window menu and choose Histogram, and that will allow us to track the Luminance levels throughout the image. So the Histogram is of course a bar graph of all of the Luminance levels that we have available to us. Just to make sure that we can see as many Luminance levels as possible, I want you to go to the Histogram palette menu, and I want you to choose Expanded View, so that we are devoting 256 pixels to the width of this Histogram that is 1 pixel for everyone of the Luminance levels inside of an 8 bit per channel image.
I am going to go ahead and collapse my Color palette. And now let's go ahead and double-click on the icon for the Channel Mixer dialog box. Now I want to make sure that I am seeing the Channel Mixer dialog box in it's entirety as I am here. And I want to be able to see the Histogram palette at the same time. Now this dude is a big image hog as we well know by now. He is smushing her. So I am going to go ahead and drag the image over a little bit so that we could at least see part of her. I am not sure that I want to see half of her eyes. So let's for aesthetic purposes here let's just see one of her eyes, and of course her nose and her mouth as well this guy's entire face, bless him.
Now here is what I am going to do. I am going to go ahead and raise the amount of Red inside of this image, because this is a portrait image I want to emphasize the Red Channel. And so I've raised that Red value to 60%. You can see there are total is now 120%, all right. So that's too much when we think. Anything over a 100% is worth a warning. We also have our Histogram palette up here which is a Cast Histogram, meaning that is not a 100% accurate. In order to update the Histogram so that it represents the image at the present moment in time, you can either click on this Caution icon or on this sort of Revolving Arrow icon right there. Either one will update the Histogram, so it's just basically slightly modifies the Histogram.
You can see that the Histogram does run up against the right edge, meaning that we have clipped highlights. So this is no good. We need to take down one of the values. I am going to tab down the Green, I am going to take that value all the way down to 0. So I am going to take it too far down. Now, notice that we are missing this whole range of highlights here inside the Histogram. Also witness by the fact that the image is awfully gray, it's very muted on-screen. Now I am going to tab down to Blue, and I am going to take that Blue value up. And I am Shift+Up Arrowing until I have a Blue value of 70%. So I am taking it through the roof here. So we have 60% Red, no Green, and 70% Blue. That's a total of a 130%. That's too high as we can see, if we were to go ahead and update that Histogram. We do have a big spike over here on the right side thus indicating that we have blown highlights.
So I am going to return into the Green value here, Shift+Tab to it. And then I am going to take that Green value down. So I am Shift+Down Arrowing until I get a total of a 100%. So that means taking the Green value to -30%. Notice that you can go with negative values if you want to. You can subtract a channel from the sum of these channels here inside the Channel Mixer dialog box. It's totally acceptable if you want to go that route. Now we are still missing highlights here inside the Histogram, so that's a bad thing. Even though we have a total of a 100% which would seem to be enough in order to create a luminance balanced image. We are favoring the shadows. So we need to bring back our highlights, and I am going to let Blue do the work, and I am just going to Up Arrow. So I am raising that Blue value by nudging it with the Up Arrow key on the keyboard until we take the Histogram all the way over to the right edge.
And so we are having a little bit of clipping going on but that much. Let's go ahead and update that Histogram to make sure that it's as accurate as humanly possible here. And that looks pretty darn good, that looks like a nicely balanced Histogram, even though our total is a 106%. Now we are getting a warning down here that's telling us maybe you are going too far, we don't care. I really don't care what this total is as long as the Histogram looks good, and as long of course as the image looks good on screen as well. So this is just kind of an FYI. Just keep it in the back of your mind as you work along. Now I like this. I am going to click OK in order to accept this modification. This may not look that different than what we had before. So let's Shift+Tab away our palettes and let's do a before and after. This is the before version, this is the Industry standard RGB to Grayscale conversion. And this is our custom conversion, actually much better. We have better highlights going on inside of the image hog's face here. Also better highlights going on inside of her face, and inside of her eyes, and inside of her lips and nose and her hair especially.
Look at that hair. This is before, dim hair no good, this is after, beautiful lustrous shinny blond hair. Now that blond is better than brunette just -- as long as she is blond we might as well take advantage of it and make that hair really shine. So that's one of the many ways you can fabricate a Custom black and white conversion inside of Photoshop using the Channel Mixer command. In the next exercise, we are going to see how we can take this Custom black and white photograph and imbue it with a little bit of color in order to create a professional quality Sepia tone.
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