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Photoshop is one of the world’s most powerful image editors, and it can be daunting to try to use skillfully. Photoshop CS4 One-on-One: Advanced, the second part of the popular and comprehensive series, follows internationally renowned Photoshop guru Deke McClelland as he dives into the workings of Photoshop. He explores such digital-age wonders as the Levels and Curves commands, edge-detection filters, advanced compositing techniques, vector-based text, the Liquify filter, and Camera Raw. Deke also teaches tried-and-true methods for sharpening details, smoothing over wrinkles and imperfections, and enhancing colors without harming the original image. Exercise files accompany the course.
Recommended prerequisite: Photoshop CS4 One-on-One: Fundamentals.
Download Deke's customized keyboard layouts and color settings for Photoshop from the Exercise Files tab.
All right, in this final exercise of the chapter, I'm going to show you how to reduce the effects of JPEG compression. I've got a very, very special image for you here that's been JPEG compressed like crazy. It's called Ornamental detail.jpg. Not only did I shoot the image with a lot of compression, but then I turned around and cropped it and saved it at the lowest quality setting possible from Photoshop. So even though the image isn't that big in the first place, it's 1.5 MB, why, it is only 50K on disk.
It's really compressed like crazy, but you can see the compression artifacts too. They show up inside of this image and other images as well as 64 pixels square, so 8X8 pixel squares. I'm going to zoom in on a few of these guys down here so that we can see what I'm talking about. So this is a good example right there of an 8x8 pixel square. What JPEG does, you know, it's lossy compression. It rewrites the colors inside of an image to make the image as small as possible on disk, and it goes ahead and keeps the color of the upper left pixel in any given 64-pixel block here. Then it rewrites all the other pixels based on that pixel, and it tries to match them as well as it can to that upper left pixel, and then it goes onto the next block and does it again and again.
Now, this is a highlight along the bottom right edge of this generic holiday ornament, and you'll see, when I start zooming out from the image that it becomes more and more obvious, it is a highlight, and it becomes more and more continuous even though it looks so blocky and choppy when we are zoomed in. That's the amazing thing about JPEG is it does a grand job of fooling our eyes from a distance. So oftentimes you can't even tell what kind of JPEG Compression has been applied to an image after you print it. It just doesn't hold up.
However, the JPEG Compression artifacts as they're known, they can really cause you problems when you're editing an image. They can really, really cause you problems when you're sharpening and when you're applying other edits that are designed to exaggerate differences between pixels inside the image. That's when you really start bringing out the JPEG Compression artifacts and making them that much worst. So how do you downplay them? Well, you can apply the Reduce Noise command, as I'll show you. So let's go ahead and Shift+Tab away the palettes over there on the right side of the screen. I'm going to scoop my ornament over a little bit so we can see it. Go up to the Filter menu and choose Noise, and then choose Reduce Noise, or I could press Shift+F9; my keyboard shortcut for Reduce Noise, and that brings up the Reduce Noise dialog box right here, complete with Big Noise, which were the last settings that I went ahead and saved.
I'm going to go ahead and maximize things here. I'll increase the Reduce Color Noise value to 60%. I took Preserve Details down to 0%. Strength is at 10 of course. I'll leave Sharpen Details down at 0, and then I'm going to turn on Remove JPEG Artifact. Now, this is a pretty subtle option, but what it's designed to do is focus its attention on those 8X8 pixel blocks that make up JPEG Compression artifact as it's applied by Photoshop in particular. All right. So we've done as much as we can to the image from this panel right here. There is not really much more that I could do. I could increase the Reduce Color Noise option all the way to 100%, but then we're just going to get color bleeding, we're not really getting any positive contribution from this option anymore, so I'll just take it down to 60%, which is just a value I found through trial and error of course.
But we do have this Advanced radio button. Go ahead and click on it, and you'll notice, now you get two tabs; one is the Overall tab, which we've already investigated. The other is the Per Channel tab, which allows you to approach the noise in a second pass; you can apply second pass of noise reduction on a channel by channel basis. Let's see, where am I inside this image? Oh, I'm too high, that's my problem. Let's go ahead and move down here to the ornament itself. If you look at that ornament, you can see, especially when I click and hold on it to turn off the preview, you can see just a ton of compression occurring right there inside the Red Channel; not nearly so much in the Green Channel or the Blue Channel. We have our standard per Channel keyboard shortcuts right there.
So notice here in the Green Channel, not really so bad. In fact, I'm clicking and holding to turn the effect off, the effect of applying in that checkbox that we saw just a moment ago, this guy, Remove JPEG Artifact. The effects of that option are actually creating problems in the Green Channel. That's interesting. Then I'll switch over to Blue and I'll click and hold it, and you can see it was pretty bad. Notice there is some bad compression artifacts there. When I release, they have gone away dramatically. So the Channel, I think, that still needs a lot of help. We could work on the Blue Channel a little bit if you want to. We could take it up to a Strength value of 5, let's say, and just crank Preserve Details all the way down. Then let's go over to Red, crank it way the heck up to a Strength value of 10, and Preserve Details all the way down to 0%, and that smoothes out things quite nicely and we're getting a much smoother ornament here inside of the RGB composite.
Let's switch back to Overall, and this now persuades me then I should go ahead and back off the Strength value, and I'm going to. So I'm going to reduce this Strength Value for the composite image down to something like 5, I think, in order to bring back some of the good details. Then what the heck, I'll increase the Preserve Details function to like 50%. Looks nice. The image is holding up as well as its going to after all. Sharpen Details, I don't know. You can play with it if you want to. You could see if the sharpening is going to help you out to some degree or other. My sense is its not going to find much of anything to sharpen inside of this image, because it's looking for low level details and I'll be darned if there are any low level details inside of this image whatsoever.
Let's just try to see what happens if we bring it up to 100%; it brings out the JPEG Compression artifacts. Beautiful, thank you for that. All right. Let's just turn it down. Obviously, this option is not meant for the images that I'm showing you. All right. Now, let's take the time to go and save off our settings, especially since we applied Advanced, which is now going to be enforced for whatever settings we apply, even if we go back to Basic, they'll still be here, just like the Smart Sharpen Advanced settings, they remain intact. So good idea to go ahead and save off your settings. I'll call this Wicked JPEG artifacts, or something like that, click OK, and then make sure to choose it so you don't save over it. Now notice, because we've taken the time to select those settings right there, I'll go back to Advanced and we can see here in Per Channel that sure enough Red, Strength of 10, Preserve Details 0, whereas if I switch back to Big Noise, nope, its turned off, Strength is at 0. So we've done ourselves a terrific favor, that's awesome.
Let's go back to Wicked JPEG artifacts. We've ensured that we're not going to have any gotchas just sort of lingering inside of this dialog box. Switch back to Basic if you want to just clean things up. You're still going to apply your Big Noise reduction to the Red Channel, and click OK in order to make it happen. This is at 200%. This is the before version of the image with some awfully gargantuan, big blocky, ugly, horrible JPEG Compression artifacts, and this is the after version of the image; not best, but certainly better. I can recognize that we've got a highlight right here, thanks to the immense power and sophistication of the Reduce Noise filter inside Photoshop.
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