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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."
So here we are looking at an extreme case of Red eye inside of this photograph of my lovely beautiful children right here. The name of the image is TSS0TBLH.psd, found inside the 13 Channel Mix folder. Of course, the acronym stands for the Sun Sets On Their Blond Little Heads because it does for me, anyway. In this case, we don't have a setting sun. We have got an interior shot, and we have got a low-end digital camera, your standard rinky-dink camera. It actually was pretty nice camera. Really, it's like $400, $500 camera.
But, it's just that the strobe is mounted so close to the lens element that the light entered their little pupils there, actually big pupils because they were dilated and reflected right back into the camera lens, and we get red eye as a result, because the interior of the retina is red and reflective, highly reflective. So we got these guys have terrible red eye. We saw how the Red Eye tool did not help us out in this particular case because it tends to make pupils gray, more often than making them black. So what's the better solution, well the better solution is to invoke the Channel Mixer.
So let's take a look at our channels in the first place here, Ctrl+1 for the red channel, that's Command+1 on the Mac of course, and low and behold, we have got a lot of red going inside those pupils. Who would have guessed, given that we have red eye. Well, I think everybody would have. So the red channel is going to be your bad channel where red eye is concerned. It's the channel that needs to be fixed essentially, more than any of the others. If you are lucky, you will see the effect only in the red channel. So the pupils will light up in the red channel and they'll look great in the green and blue channels. That's something across your finger is for.
In this case, our desires are forted, our wishes go unrequited because if we press Ctrl+2 or Command+2 on the Mac in order to switch the green channel, you can see that the pupils don't look too good in the green channel. They do look a heck of a lot better, but they still look wrong and whereas Sammy's, my youngest boy Sam, his pupils look pretty darn good inside of the green channel. They look okey-doke. Max's just look terrible. Once again, it's because of those coronas my elder son has, Max. Those coronas around the pupils look just terrible. We have got really heavy black outline going on. Let's go ahead just for the sake of completion here. Let's go ahead and check out the blue channel as well. I am going to press Ctrl+3 or Command+3 on a Mac in order to switch the blue channel and we have got problems inside the blue channel as well.
In fact, the blue channel is only slightly better than the red channel. It's worse than the green channel. So we are going to do some channel mixing, but we can't expect too much from it, because we don't really have a good channel to work from. We just have three bad channels that we are going to try to blend together. I am going to go ahead and switch back to the RGB image. I am going to press and hold the Alt key or the Option key on the Mac, and I am going to click and hold on this Black/white icon here and choose Channel Mixer. I am going to call this Red Eye just because that's what we are going to do, and I am going to click OK.
Actually, you know what, I forgot to do something. I should have gone ahead and selected the pupils first, because otherwise if we start fixing things, what's going to happen, we are going to effect the entire image. So let's go ahead and generate our selection for starters and you select the pupils using the Elliptical Marquee tool. You just go in there and you start selecting things manually using the tool. It's not hard to select pupils. Actually, it's pretty darn easy if you have big pupils like this to work with. But, just because it's fairly routine and mundane, I have gone ahead and done it for you in advance. Go to the Channels palette and you will see this channel right here. This Alpha channel called Pupils. Go ahead and click on it and you will see the pupils that I have drawn for you.
If you go and zoom in, you will see that after drawing the pupils around Max's eyes, I went ahead and blurred them. I have applied the Gaussian Blur filter with a radius of 2, and because Sammy is in lower focus, he is blurrier inside the original photograph. I have gone ahead and blurred his pupils with a radius of 4. If I show the RGB image at the same time, you can see what these pupils look like and through this Quick Mask Mode here, you can see that I have gone ahead and drawn my selections larger than the pupils. So I have more room to work with. So that I am enclosing any coronas that might be surrounding these eyes.
Let's go ahead and scroll over to Max. You can see that I have gone ahead and selected his coronas as well, those hard edges around the pupils. All right. So back to the RGB image. Turn off the mask, and then Ctrl+Click or Command+Click on that Alpha channel in order to load it as a selection. Now, let's go back to the Layers palette. Let's zoom out a little bit here so we can see both of the boys. Now, I am going to once again Alt or Option+Click on the Black/White icon and choose the Channel Mixer function, and I am going to call this New adjustment layer Red eye, and I am going to click OK, and notice that it's automatically assigned to just the selected region of the image. So we have a layer mask that Photoshop creates for us.
Now, I could go ahead and try to dial in a Monochrome version of the pupils, and I could sort of take a lot of the color out of there like so. That is, I could take a lot of the brightness out of those pupils. But, if I do, notice it's going to look pretty gummy and weird. It actually doesn't look good. It looks like, remember Rudolph, the Red-Nosed Reindeer, that Rankin-Bass Production. And remember how Donner or one of those darn, lovable reindeer grabbed a clump of mud and threw it on his son's nose? I think, that's what we have done.
That's pretty much the equivalent except I have taken a couple of clumps of mud and thrown them in my kid's eyes at this point. I am worse than Donner. I am worse dad than Donner man. Donner was kind of a jerk of a dad, I have to say. All right. So anyway, we don't want to use monochromes basically where it comes down to them. I am going to go ahead and turn off that check-box. Notice that turning off the check-box isn't enough. It goes ahead now, Photoshop says, Oh! Well, I think you want a negative 2+21+ 20 in my case on a red, green, and blue basis. I will go ahead and apply it to every single one of the channels. So in another words, makes more work for me having done this.
So I am going to go ahead and press and hold the Alt key or the Option key on the Mac and click on that Reset button, formerly canceled. It becomes Reset when you press the Alt or Option key. So what we want to do is, we want to dial in values for red, green, and blue independently. I am going to take red out of the Red channel because we don't need any red channel at work inside of these pupils because red channel is where the pupils are basically white. It's not doing us any good. So I am going to change the red value to 0 and I am going to change the green value to 80%, and the blue value to 20% like so. Then, I am going to go over to, the green channel is fine at 100% right now. Then, I am going to go over to the Blue channel and I am going to change it to 60%, and also 40%. So oops, 40%, so 60% green, and 40% blue.
That ends up darkening the pupils a little bit, and more or less neutralizing them. Although, you might see that there is a little bit of a purple cast going on, especially compared with a green of the irises. Now, neither of my children have green eyes as it turns out. However, inside of this photograph, they are both looking green. Sammy actually has brown eyes, and Max has blue eyes. But, for some reason, they are both showing up the shades of green inside of this photo. So we want to make the pupils a little greener as well to match. So here's what I decided to do. I decided to take 3% worth of color out of both green and blue inside of the blue channel. So I took these values down to 57% and 37% respectively, and then I went to the Red channel, and I took them down by 4.
So 76% and 16%, and I am doing that of course by nudging the values using the Down-arrow key. Then, I went over to green and I raised that value a little bit. I took it up to 102%. Now, you can see that they have a little bit of a green cast. It actually more or less neutralizes this right hand pupil, Max's left pupil of course. But, it makes the other pupils a little bit green, which is fine, which is better than the alternative. So I will go ahead and click OK at this point. Now, if you are lucky, if you had some good stuff to work with inside of the Green and Blue channels, this would pretty much take care of your problem. Now, it wouldn't necessarily be those exact values, but it would be values in that range.
In other words, you are going to back off the content of the Red channel. You are going to put blue and green into the Red channel, and then you might have to put some blue and green into the Blue channel, and you are probably going to leave the Green channel more or less alone. That's kind of standard when you are fixing red eye. However, in our case, it doesn't do the trick. It doesn't completely take care of the problem because we don't have red eye anymore, but we do have that gray eye effect and we also have some pretty bad coronas around Max's eyes. Now, I could go ahead and try to sink that by setting the Blend mode to Multiply, but then we get our red eyes back and it looks terrible. We could try some other modes too like Linear Burn, but that's just going to look wrong.
So we're better off just leaving the Blend mode set to Normal. Instead, what we are going to do, as I say, if you are lucky, that's going to solve your problem. If you are not lucky, in our case we aren't, and it doesn't solve your problem, then you need to apply some additional modifications to those pupils, and we are going to apply those additional modifications in the next exercise.
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