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Here's the sharpened version of the orange on blue snake from the previous exercise. Now were you to inspect this image very carefully, you might start to notice that there are some color disparities showing up inside the image so in addition to sharpening the edge detail, the Unsharp Mask command has also brought out some color anomalies and they are very subtle as it turns out but they are evident inside this image but subtlety be darned.
I figure I am going to show you when I am talking about more obviously inside of a totally different image here, so I would like you to switch this image, it's called barehead.jpeg, it's also available to you inside the Elevensharpen folder. Now this image I shot, I photographed this one, it's a bare head on a wall unfortunately dead animal I am afraid. Now if you check out its fur, I am going to go ahead and zoom in on the fur here. It looks like it's fairly uniformly sort of orange and warm, doesn't it? Turns out that there are some slight color variations going on and some rather cool shades going on inside of this fur as well and that's the kind of thing that the Unsharp Mask command and any sharpening functioning for that matter tends to exaggerate and I want to show you what I am talking about.
So let's go up to the Filter menu and notice now that the first command at the top of the Filter menu is Unsharp Mask. We could repeat the last settings we applied by pressing Ctrl+F on Command+F on the Mac or if wanted to bring the dialog box back up on screen and apply different settings then you would press Ctrl+Alt+F or Command+Option+F. Let's go ahead and do that. I will go ahead and escape off the menu here and I would press Ctrl+Alt+F on my keyboard in order to bring up the Unsharp Mask dialog box once again.
And I am going to apply some very exaggerated numbers here. I am going to zoom out from the barehead inside of the in dialog box preview and I am going to focus in on his eye here and I am going to take this amount value up to 500% and I am going to raise the radius value to 4 and I am going to take the threshold value down to 0. Alright so these are some very exaggerated values but go ahead and check out what the barer looks like. I am zoomed in now to the 100% zoom ratio. Not only am I bringing out a lot of noise which one would expect given the high amount value and high radius values but I am also bringing out a lot of weird colors inside the bare and there is nothing special going on inside of this image.
This is the way it is. I didn't prep this image to make it specifically behave this way. It just has this quality about it and what's happening is that Photoshop is exaggerating color problems that were already inherent inside the image. They were just so subtle that we couldn't see him but now that we have sharpened the image we really can't see the problems. So alright, I am going to go ahead and click OK in order to apply those exaggerated settings. What's happening here is that Photoshop is going through and sharpening the red channel, the green channel and the blue channel independently of each other.
Check out that blue channel. What a mess? Now I photographed this image using a midrange camera, so not a really super deluxe model and mid-range cameras often hide a bunch of garbage inside the blue channel and that's what's happened to this image. So this is the before version of the blue channel, still really bad and this is the after version, thanks to the Unsharp Mask command and thanks to the horrible mess of this blue channel. We are having a lot of color mis-registration going on in the composite RGB image and as a result we are seeing blue and purple up here inside of the hair.
Alright I am going to zoom back out because we can see it clearly from pretty far away here. Alright I am going to show you two fixes for this effect. I am going to undo the Unsharp Mask command. First I will show you a very popular technique for avoiding color sharpening and strictly sharpening the luminance levels inside of an image and then I will show you what I think is a better and certainly an easier way to work. Alright so here's the common technique, starting with an RGB image go up to the Image menu, choose mode and switch to L-A-B color or LAB color if you prefer.
And that divides the colors inside of an image into 3 different channels, lightness which is all the luminance levels then we have got A and B. Now they don't look like much but there are different color variations. Basically B is showing you your temperature variations between blue and yellow and A is showing you your tenth variations between green and magenta and we will look at temperature and tend to more detail when we take a look at Camera but for now if you want to see what their contributions are you can just turn on like A and lightness at the same time and then you can see that A is contributing the greens and magentas.
I will turn off A and I will turn on B and you can see that B is contributing the yellows and blues. Alright, doesn't really matter because always care about is lightness, so what I want you to do is this, starting in the LAB, the composite LAB image, click on the lightness channel here inside the Channels Palette and then click the eyeball in front of the LAB image so that you are seeing all the channels but you are only modifying the lightness channel. Now go to the Filter menu and reapply the Unsharp Mask command. You don't have to press Ctrl+Alt+F or Command+Option+F this time.
You can just choose the command or press Ctrl+F and notice what happens. This time the exact same settings and amount of value 500%, a radius of 4 and a threshold of 0 and we are not exaggerating the color disparities at all. We are only focused in on the luminous levels inside the image. Alright, so that's one way to work. It's a good way to work. There is nothing wrong with it except it's kind of a multistep operation and in that regard it's a little bit inconvenient. My preferred way to work is not only a little more straightforward and involves fewer steps but also it provides a little more flexibility as it turns out.
So I am going back-step I am going to press Ctrl+Alt+Z, Ctrl+Alt+Z a couple of times there to restore the RGB version of my image that would be Command+Option+Z twice on the Macintosh side of things. Now here I am back in the RGB image. I am going to reapply the filter once again by just choosing the Unsharp Mask command from the Filter menu. It's going to look right and it's going to look horrible. Now go to the Edit menu and choose Fade Unsharp Mask. Brings up the Fade dialog box which allows you to merge the after version, the Unsharp Mask version of the image with the original version of the image.
Now I am going to start things off by modifying the mode setting here. I am going to click on the word Normal and notice these guys down here Hue Saturation Color and Luminosity. Now as we have seen in the past color is made up of Hue and Saturation working together. Where I to apply my modifications just to the color, I would just bring out these color anomalies and I would not affect the luminance levels at all. The opposite of color is luminosity right here, if I choose it I will only affect the luminance levels and I won't affect the color at all and that's what I want.
So go ahead and choose luminosity, notice what it does, those colors fade away. We get the original colors inside the bare. We apply the Unsharp Mask command just to the luminance levels and here's where I say thanks for more flexible. Now that I have seen that luminosity takes care of my problems I can back off my affect. I know I went way too far with it, right, I didn't want an amount value of 500% and a radius of 4, that's ridiculous. So I will go ahead and tamper my affect by reducing the opacity value. I can apply both operations from one dialog box with convenience and I didn't have to go onto the LAB mode so it's totally awesome.
I will click OK in order to accept the affect. Now I am going to go ahead and show you before and after version of my sharpening. I will press the F12 key to load the original image, the one that was saved to disk and then I would press Ctrl+Z or Command+Z in order to show you the sharpened version, thanks to the Unsharp Mask filter and the Fade command set to the luminosity blend of mode and a lowered opacity value.
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