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Based on the device-independent CIE specification from 1976, Lab color is frequently misrepresented as a techy, labor-intensive color space. In fact, Lab color performs certain types of color modifications more quickly and with better results than RGB. In Photoshop CS3 Mastering Lab Color, Deke McClelland explores how to use Lab color "to make bad photographs great and great photographs even better." He demonstrates image manipulations that are best suited to Lab, and walks through a typical, non-destructive Lab correction. Deke also shows how to correct lighting, apply selective color modifications, and reverse the effects of color cast. Exercise files accompany the course.
All right, in this next exercise we are really taking the correction to the mat. Once again we are just trying to do the best correction conceivable at this point. We are going to remove a problem that's barely visible but it could turn into a worse problem once we print the image. I'm not sure if you can see. I'm begging your indulgence at this point of time. I'm not even sure you can see this problem in your video and by the way, I'm working in a progress document called Smartly filtered.psd found inside the 03 Typical Lab folder and this image is smartly filtered of course, we have got a collection of three Smart Filters in all.
All right, what you may be able to make out on your screen, if not inside the video here, if you are working along with me, is a slight wavering between the white and the yellows inside of this image. This is a function of Medianed JPEG compression artifacts and it's really showing up. I'm going to press Ctrl+3 or Cmd+3 on the Mac. It's showing up worsen side of the B channel. Can you see it? Well, possibly not. So, let me dRAW it out for you. Let me make sure that you can really see it. I'm going to switch back to the RGB composite by pressing Ctrl or Cmd+Tilde. I'm going to go to the top of the adjustment layer stack and I'm going to Alt/option-click on the black white icon, choose Levels and I'm going to call this guy tester.
This is a really great use for adjustment layers incidentally. It's to test problems inside of an image. We don't intend to keep this adjustment layer. We are going to turn it off. But we are just keeping it around. We are just creating it in order to test the problems as I say. So click OK and now I'm going to go over here to the B channel because that's where a problem really resides is inside the B channel and I'm going to change the first value to 100 and the second value to 155. So this is going to make our image look a mess, really I mean it's going to mess up the colors in the image as you can see over here in the Navigator palette, but it demonstrates the problems that we have in the sky.
Can you see it now? If not, let's go to lightness just to make sure you can really see it. Now, I'm going to increase this black point value to let's say about 190. Now you should really see the problem showing up there in the sky and I will click OK. Now, that's not how we want the image to look but it does test out this problem that exists here. What do we about it? Well first, what created this problem in the first place ironically the Median command created the problem. The Median Filter did, notice, if I turn off Median down here at the Bottom Layers palette. Watch what happens inside this region here. It might take a moment to update.
Notice that we have a lot of noise now inside of this area but we don't have that blockiness. Now, some people might say well, that's because you use Median but what you ought to have used in order to smooth over the noise, you ought to have used Gaussian Blur, that's actually not true. Let me show you. I'm going to go ahead and click on the Lab Smart Object there. I have got Median turned off. I'm going to go up to the Filter menu. I'm going to choose Blur and I'm going to choose Gaussian Blur. We will see that we are going to get goops associated with Gaussian Blur as well. They are just rounder instead of being squarish. Problem is anytime you are averaging pixels no matter what kind of command you use to do it, you run the risk of actually exaggerating certain kinds of noise inside of an image particularly here inside of Lab.
So, I'm going to go ahead and cancel out of this. So what do we do, because we need median, we got to have median because otherwise we have got all kinds of color noise and chromatic aberrations that are showing up elsewhere in the image and it's the best command to take care of it. By the way reduce noise, that wonderful elegant Reduce Noise command, which is really a great command, has the same problems. It's going to make those kind of blocks show up as well. Check it out if you want to. Anyway, I'm going to turn Median back on just by pressing Ctrl+Z or Cmd+Z on the Mac and I'm going to leave tester there. For now, I'm not going to throw it away in other words, but I'm going to go ahead and turn it off for the moment.
The reason is because I want to go ahead and load a density mask. So we are just going to sharpen the darkest portions of this image. So there is we are just going to filter the darkest portions of the image and we are not going to worry about these light areas, so that the light areas stay nice and flat. So what I'm going to do is I'm going to go ahead and just leave everything turned on except for the tester layer. Then go over to the Channels palette, and I want you to Ctrl+Click or Cmd+Click on the lightness channel in order to load it up as a selection outline. So, Photoshop has now gone ahead and selected the lightest portions of the image.
That would be a Luminance Mask if you are familiar with my masking series, very distinguished Luminance Mask from Density Masks. You know that this is a Luminance Mask. We are selecting the lightest portions of the image. I'm going to go to Select menu and to convert a Luminance Mask into a Density Mask, you choose inverse just like that, and then you select the darkest areas in the image. Now, go over to the Layers palette or right click on Smart Filters right there. Right click on the word Smart Filters and choose Add Filter Mask in order to reestablish a filter mask, but this time the one that actually does something inside of the image.
I will go ahead and scoot over a little bit here. Now notice, if I turn on the tester layer that we don't have nearly the problems that we had before. So Shift+Click to turn that Mask off and then Shift+Click again to turn that Mask on. I'm Shift+Clicking on the Mask itself by the way on the Filter Mask and you can see that, that goes a long way towards solving our problems right there. Now, I'm going to go ahead and click inside the image to make it active and then I will turn off the tester layer, that's what is causing these problems right here and go ahead and zoom out from the image. You can see that we still have a nicely sharpened version of the image.
Some of the chromatic aberration is restored but it's not too bad and we are just sharpening the darkest details. I'm just going to click on the eyeball in front of the Smart Filters there. This is what it looks like without any of the filters and this is what it looks like with the filters turned on. Alright, so done a really nice job of correcting everything about this image except for one thing, the image needs to not have this blob, this little sort of fingerprint on the window here that's showing up at the top of the image. Also, we need some cropping because you can see around the edges if you look closely we have a little bit of transparency showing through, this is because the image got distorted slightly when we applied the lens correction function.
So, we're going to crop the image and make it look just picture perfect in the next exercise.
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