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If you shoot your digital photographs using the raw format then you can take advantage of CS5's Lens Correction profiles inside of Adobe Camera Raw. This has the advantage of applying transformations to the camera data before it is processed. The upshot is a higher-quality result instead of doing this operation post raw conversion. As a bonus ACR, can be used to do additionally open JPEG and TIFF images, but remember these images have already had the camera process them.
So we're going to work with a raw file and I'm going to go to the exercise files here in chapter03, and we're going to use mansion.CR2. CR2 is just an extension that indicates it's a Canon raw file. Depending on your camera you may have a different extension, but it's just a way of identifying raw files. So let's double-click this, and this opens us up into Adobe Canon Raw commonly known as ACR. What we're going to do here is take advantage of ACR's ability to apply a lens correction profile to the image.
However, because as I said we're in the raw converter, we're doing this before any processing is done. The result is going to be a higher-quality image. So let's go over to the tab here that looks like a little set of lenses, Lens Corrections, and we'll click on this, and we'll enable the Lens Profile, and watch what happens to the image. You saw that it? It just changed it. I'll click it on and off so you can see. It's taking out the lens aberrations that are part of, in this case, the Canon 17-40 lens, and in doing so, it gives us a truer representation of the image.
I'm going to show you another secondary effect that happens here. Let's go up to 100%, and I'm going to move this over where we can see the tree branches. I will probably even enlarge it a bit more. And let's temporarily turn off our Preview. You see what's happening here in the colors. We're getting this fringing, and this is commonly known as chromatic aberration. What happens is when the lens, especially at the outer peripheries of this wide angle lens, when the light comes through it, the lens has to, just by the nature of glass, slightly bend the different parts of the light spectrum minutely small angles, but they do make their appearance in the form of chromatic aberration, and that's what we're seeing here, this typical green-purple fringing.
Now when we turn Preview on, you can see it's completely eliminated the fringing. So it takes all of these lens optic peculiarities into effect for this specific lens and breeds out all of these types of distortions. And the benefit is by doing it at the front end before a processing happens, you are going to end up with a higher-quality image in the end. It's not a make or break thing if you don't work with raw files. It's just nice to know that you can go to the level of dealing with a raw file and be able to process it in a manner that is the least destructive to the data that you have to work with.
Once I'm done with all of this, I can go ahead and open the image, and that we'll open it for us inside of Photoshop with those corrections applied. So now I could take this, for example, and use the free transform that we played with in the last video to get these distortions out that were caused by the way the camera was held and tilted the camera sensor at an angle away from the building. So all of these various kinds of things come together to be able to start off with polishing your image up to get it to the best quality you can before you make that big conversion from a photograph to a painting.
Now lens distortions are usually subtle, but can distort image view in a photo. Whether you shot raw or not, lens profiling is available in the form of ACR's Lens Correction panel on the Filter menu's Lens Corrections filter.
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