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Photoshop CS5 One-on-One: Advanced, the second part of the popular and comprehensive series, updated for CS5, 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 CS5 One-on-One: Fundamentals.
In this exercise, we are going to take a look at two remaining lens correction options, specifically Lens Vignetting and Chromatic Aberration. Now, I have opened that corrected version of Interior pool.dng found inside the 24_camera_raw folder. I have already switched over to the Lens Corrections panel and I've clicked on the Manual tab so that I'm seeing these manual adjustment options. If you drop all the way down to the bottom, you'll see Lens Vignetting. The idea here, a vignette is a darkness around the perimeter of the image.
Typically, it's a darkness. It's a shadow that's cast by the lens onto the image, but it could also be an unnatural highlight around the perimeter of the image as well. You're going to see that shadow or highlight in the corners. So it's almost like this big radial gradient starting from the corners and fading away to the interior. Now as often as not, you see people add vignettes to their image. So frequently, folks will use this Lens Vignetting option down here to add a vignette effect.
I have to say I personally frown on that technique. I'm not a big fan of artificial vignettes. In fact, this option was designed to get rid of vignettes, not to add them. But you can do whatever you want. Anyway, I will just show you how it works. I'm going to increase the Amount value, because in the case of my image, we do have some dark vignetting around the circumference of the image. So I'll increase that Amount value to, let's say, 60. Actually, it works out pretty well. Midpoint allows you to shove the effect outward or inward, if you want to.
So if you shove the effect, you're going to apply a lot more lightening to the image, because you're extending the lightening effect towards the center of the image. If you shove it outward with a higher midpoint value, then you're going to get less of a lightening effect. Anyway, I am just going to leave it set to about 50%. That works out pretty nicely for this image. However, for those of you who are vignette enthusiasts and you want to add vignettes to your image, then you go ahead and reduce the amount value so that you get this hideous effect. What is the attraction? I do not understand.
Anyway, I'm going to reset Amount back to 60, because vignettes are bad and I want to get rid of them. All right, we have the option, however, of applying post-crop vignette effects inside of Camera RAW 6. So I will be showing that to you, but for now let's stick to the corrective techniques. I am going to go back to San Simeon pool.dng. I am going to zoom in on this facade, this distant facade in the background here. As I zoom in, you're going to notice even if you've never heard this term before, you're going to notice the effect.
It's Chromatic Aberration. See how we have these colors that are just absolutely out of alignment with each other. Right along the top of this facade, you can see that we have a magenta edge and then below, we have this kind of cyan edge. What in the world is happening there? Well, the colors are out of alignment toward the perimeter of the image. So this is another perimeter effect. As opposed to lens casting a shadow or creating an unnatural highlight, however, this time the lens is distorting the colors slightly.
So when the image is interpreted and demosaiced and converted from the linear raw data into the independent RGB channels, well, that information isn't aligning quite right. It should be with any luck it's aligning just fine toward the center of the image because that's where the light is best focused. It's going out of alignment toward the perimeter. We can fix for this effect inside a Camera RAW, and actually we can do a brilliant job. Camera RAW is very good at this using these Chromatic Aberration options. Oftentimes, the big problem is knowing which slider to use.
That's usually going to be a combination of the two, but is this a red/cyan fringe? It's actually kind of magenta and cyan, I'd say. Or is it a blue/yellow fringe? Well, it doesn't look blue and yellow. So it's looks more of red/cyan. Finally, do we move the slider triangle this direction or do we move it the other direction? What's going to end up giving us the best effect? Well, it looks like where this image is concerned, the effect gets worse if I drag the slider triangle to the right, and it gets better if I drag the slider triangle to the left. Here is another technique you should know about and this is as a top-secret trick.
Really helpful I find. You press the Alt key or the Option key on the Mac and you drag this slider. Now it doesn't look like much if anything is happening back there in the larger image window, but we are basically distilling the image to just reds and cyans. As soon as that edge, the edge in question, the edge that's offending us here. As soon as it turns nice and neutral, or as neutral as possible, then we are losing that fringe effect. We are losing the Chromatic Aberration. In about -40, I'm seeing a pretty neutral edge going on there.
And I'm looking at the top of that triangle once again, the triangular facade. I will go ahead and release. That looks like it takes care of the effect pretty nicely. Then we might as well toy with this Fix Blue/Yellow Fringe too, because there may be another fringe we are not really aware of. So I if drag this option, I am pressing the Alt key as I do this, the Option key on a Mac. If I drag the slider triangle all the way to the right, then I'm definitely exaggerating whatever effect I had. If I drag it over to the left, it's going to start getting bad as well if I go too far, but at about -5, so this is a pretty subtle effect, I'm seeing a fair amount of neutrality along the top of that facade.
So I've got a red/cyan fringe value of -40 and a blue/yellow fringe value of -5. Let's get a sense of what we've done here. I will go ahead turn the Preview check box off. This is the original fringed edge here, the original chromatic aberration, and this is the reduced effect. Now you may have noticed that the scene seems to be jumping up and down a little bit. I will go ahead and zoom out a click here, and that's because Camera RAW is actually rotating the various color channels into alignment with each other. So it is changing the orientation of the scene a little bit.
So again, this is the before version of the image. Notice it's kind of catawampus as well. You can see these alarming color fringes going on, magenta and cyan. This is the corrected version of the scene. Thanks to the just infinite power of manual lens corrections here inside of Camera RAW.
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