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Removing lens distortion with the Adaptive Wide Angle filter


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Removing lens distortion with the Adaptive Wide Angle filter

Every lens distorts the scene whose light passes through it. Some more some less. The fact of the matter is, that a photograph does not record what we see but how the lens optics bend the light onto the plane of a camera sensor. The Adaptive Wide Angle filter, also known as AWA, provides a tool for massaging various lens distortion effects out of an image. In this video, we'll take a look at how to take advantage of this useful tool. To find Adaptive Wide Angle filter, go to the Filter menu, and go down right here to Adaptive Wide Angle.

This will open up its own dialogue that is a little world we're going to work in while we're in Adaptive Wide Angle. I have it on auto and that's generally where you want to put this. What its doing is its actually using from your camera, and you may wonder where it gets that information? Formats like JPEG, TIF, RAW, all encode some of this camera specific data into the file. If we look down here at the lower left corner, you'll see it knew that this was my Canon 5D. It knows that its actually 17-40mm lens.

So, it has all the information about this lens, and using that, it's applying it to this image. So we're all, we've seeing some distortion in there, but with a knowledge of what the lens actually is doing to this image, and these tools, we can massage these errors out of the image. And in the case of this image, I'm approaching this whole project from a more of what I call an illustrative point of view. And by that, I mean, I am not going to utilize the keystoning, as it's called, where the lines of perspective in this image, particularly the vertical lines of perspective, all seem to have a point off up in the sky somewhere.

I want all of those lines to be straight. Much like an illustrator would draw this, as we talked about in the language of photography and painting earlier, I mentioned that these are things that our eye typically doesn't see. As artists, we tend to remove these errors out of the image and that's what we're going to do here. So, in order to make this l ook like a painting, I have to breed this photographic vocabulary out of the image. And how do we do that? Basically, we're going to be using the Constraint tool up here at the top, that's the key tool to this.

And you'll see I'm going to start from one edge here, I'm going to draw across. Now notice, see how that line's bending? That's because it has the formula for this particular lens and it knows that that has a natural angularity to it. When I let go, it goes ahead and it straightens this out. The thing I want to do, and by just selecting any area near the line if I click with my right mouse key, I can decide how I want this to be oriented. And, in this case, I want it to be exactly horizontal, so I'm going to say Horizontal. And you might have seen there, it just did a slight shift.

So, once that turns to yellow, that tells us this is an exactly horizontal line. So the first part of this is to go through and go through some of the key areas of this image, and straighten these out, and in each case I'll go back and I'll say, I want this to be horizontal. And so, it's really a pretty much kind of a rote exercise to go through and set each of these up. Now, you can do as much or as little of this as you want. I tend to be a little bit obsessive about it and I will go through, and if I want this to be very rigidly horizontal and vertical lines, then I have to make sure that anywhere I see something that doesn't seem correct is corrected.

And so, it's just a matter of going through all these. So, I'm going to go ahead and go through this and get all of the horizontals done, and then we'll come back and I'll go ahead and do the verticals. So, I've done all of the horizontals that I basically want to do here. I may need to add one or two once I start putting the verticals in, but I do want to show you, if you turn on the mesh here, you can start to see how it's bending that mesh around to conform the image to the horizontals that I want to do.

So, it's actually doing quite a bit under the hood here, but the visual aspect of it is fairly clear. It's just setting everything up so it's on horizontal. Now, I'm going to go through and I'm going to start dealing with all of these verticals. So, same thing here, we go ahead and click and drag. And, just as I did before, I right- click on that line and I set it to Vertical, and that sets it to purple. So whenever it's purple, that's telling us that it is a exact vertical line.

So, I'm going to go through and do all of the verticals here, and then we'll take a look at what we've got once it's all finished. Okay. So, I'm pretty much done here. I do want to show you just one little trick that I didn't mention at the outset and that is, when you make a line, I've actually removed one here temporarily so I can straighten it out. If I hold down the Shift key, whether I'm doing a vertical or a horizontal, see how it's already yellow? That's telling it that this is supposed to be a horizontal line, in this case.

So, if you want to not make this into a two step operation where at first you apply the line, then go back, right-click to tell it whether you want it to be horizontal or vertical, you can go ahead and utilize the Shift key to do that in advance of making it be a vertical or horizontal line. So, we've gone through this and the last thing I do wanna say here is that I was being pretty obsessive about this, and this is also a very unusual subject in that it's really got a lot of horizontal and vertical elements in it that, at least, I want to make horizontal and vertical.

So, different subject matter, you may not have to go nearly to the length of the number of lines that I've ascribed to this particular image. It's all very image-dependent and its up to what you ultimately are looking for vision-wise in your image. So, once you are done with this go ahead and say, okay. And it will apply all of these calculations to the image, so that we end up with a corrected image. So, if I do a before and after here, you can see how we've taken all of that distortion that the lens introduced, being a wide angle-lens, and I've straightened it up to more like the way I would have sat and drawn this image.

I wouldn't have drawn it, as I said earlier, with all of these lines going off into some perspective. I would have drawn it more like that. So, the Adaptive Wide Angle filter rids and image of lens distortion, but it also enables user-dictated adjustments. In our example, we altered a lens-distorted image to a more illustrational style of orthogonal rendering.

Removing lens distortion with the Adaptive Wide Angle filter
Video duration: 6m 47s 4h 46m Intermediate

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Removing lens distortion with the Adaptive Wide Angle filter provides you with in-depth training on Design. Taught by John Derry as part of the Digital Painting: Architecture

Subject:
Design
Software:
Photoshop Wacom
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