Distortion City! (and how to cure it…)

One of the most difficult subjects for today’s Point and Shoots, even the most advanced (maybe especially the most advanced with their superzooms) is architecture. This was brought home to me after a recent visit to Germany where I was pretty much confined to photographing the Old Town in Wetzlar (and a cloister/hotel in Lich). Very picturesque…but, with its exposed beamwork, tall thin buildings, narrow streets, and stone walls it is subject matter which brings out absolutely the worst in todays’ modern zooms. Curves replace straight lines everywhere. Buildings lean into the frame at crazy angles. Walls waver and bulge. Shooting from street level on narrow cobblestone streets the perspective distortion alone is dramatic…when you add the distortions of a P&S zoom, things get more than a little crazy.

Example.

Crazy Distortion!

I really like these buildings, this street, and I can live with the distortions of the lens I was working with. It is still a satisfying image, in my opinion, despite the really severe distortions displayed. I mean, look at the buildings at the end of the street! Nothing in nature or in architecture looks like that! Part of it is perspective, but part of it is the unique set of distortions of my H50 zoom at full wide.

Of course, since such zoom distortion is so common today in images we see published, and since, without special perspective control lenses that only pros who specialize in architecture use, any image of buildings like this will show massive perspective distortion, we have begun to take such distortion for granted. It is part of the image. We are over it. It is not that we do not see it…it is that we make automatic, even unconscious, allowances for it.

And distortions like this hardly effect my landscapes and macros at all. They are there but it takes rectangular objects stacked and a close horizon like…well like buidings in Old Town Wetzlar along a narrow street…to bring them really to the forefront.

So, I have two choices. I can enjoy the tourist style shots of the Old City for what they are, distortion and all, or I can attempt to fix it in software.

Until this past week, fixing in software for me was not an attractive option. My little Acer Aspire One Netbook, while it handles general processing and cataloging in Lightroom just fine and has made me a happy mobile photographer for quite some time, simply chokes on a task as mathematically intensive as adjusting the perspective and distortion of an image…even using PhotoShop Element’s excellent Camera Distortion Filter. For me it is complicated by the fact that Lightroom is my primary tool. Lightroom lacks distortion filters, so I have to open the file in an external editor (Elements in my case), work on it, and save it back to my Lightroom catalog. Lightroom makes the process very easy, but having both Lightroom and Elements open on my netbook at the same time, and doing any complex task strains the resources of the computer to the max…past the max too often. Even if it works, a lot of time is spent waiting while the computer thinks about whether it is going to work. And the alternative, saving the Lightroom version to drive, closing Lightroom and opening Elements, opening the file, doing my thing there, saving the image back to drive, then reimporting it into my Lightroom catalog…well, since my processing time is limited by my real job, and I have a family that wants some of my attention, it would have to be a very special image for me to do all that!

Last week, though, I upgraded my travel laptop/netbook. You will undoubtedly hear more about it in a more comprehensive review at some later date, since it is already revolutionizing the way I deal with images (as in this case), but suffice it to say for now that I can now work with Lightroom and Elements at the same time, flipping back and forth as needed, and both programs are, by my standards (which are probably low compared to a pro), satisfyingly responsive even on the most complex tasks.

(Okay I won’t keep you in suspense. It is an Atom powered HP Mini 311 with Nvida ION graphis; an 11.6 inch, 1366×768 (16/9 ratio) screen; and 3 gigs of memory. My new travel/photography computer.)

Now that I have the equipment, I decided to attempt some distortion control on a few of my favorite Wetzlar shots.

This is the image above, processed with PhotoShop Elements Camera Lens Distortion filter set.

Perspective and Distortion controlled version

Distortion and Perspective controlled version

It is still not perfect. I might go back and rework it a bit more, but it is way better, at least from a distortion perspective (pun!) than the original. The buildings don’t lean crazily any more. The lines are more or less straight, and the walls apparently vertical. I accomplished this in about 2 minutes using the filter in Elements.

Whether it is a better image than the original is a matter of personal taste and photographic philosophy. I think I like it better. I think, right at the moment, that it was worth the effort of correction. I think, if I were to make a print to hang on the wall, I would prefer the corrected version. Of course, on mature reflection, that might all change. We shall see.

What do you think?

I am going, for anyone interested, to walk you through processing out the distortion in an image using the Correct Camera Distortion filter in PhotoShop Elements.

The first step, if you are working in Lightroom, is to have Lightroom make a copy with your Lightroom edits and send it to Elements. It is a two click process. If you are working directly in Elements, just open the image.

This is our starting image.

Where we start

The Correct Camera Distortion filter is in the Filters menu. The open dialog looks like this. Click the image here to see a full screen view.

Correct Camera Distortion filter dialog: Elements

As you can see, you have several distortion controls at your command, beginning with Distortion (which controls barrel and pincushion), down through vertical and horizontal perspective, vignetting and edge stretch. The best part though is the fine grid laid over the image and the fact that you can watch changes you make happen in real time. All you have to do is adjust the controls so that verticals match the upright grid lines and horizontals match the lines across, and then adjust edge stretch so the frame is filled once more.

I always start with perspective. In most shots it will be vertical perspective that is noticeably off. Experiment with the slider. As you can see in the screen shot, the slider stretches one edge (top or bottom) of the image and shrinks the other. Slide it until the verticals in the image more or less match the verticals in the grid.

Slide to adjust the verticals in the image.

Once the perspective is more or less correct, you can adjust distortion. Distortion turns straight lines into curves, and warps objects at the edge of the frame. Slide the slider until lines that should be straight are.

Slide the distortion control until straight lines are straight

After adjusting distortion you may find that the perspective no longer looks right. Go back and readjust if needed.

A second perspective adjustment may be necessary

Finally you can use the Edge Stretch control to stretch the image to fill the rectangular frame, effectively cropping off the curved edges of the corrected image: then apply the whole effect with a single click. Alternatively, you can leave the Edge Stretch tool alone, apply the filter, and then manually corp out the undistorted center of the image.

And that’s it.

And where we got to...

I should say that the peak of the building on the right is actually quite off kilter in reality.

Here is another example of an image that benefits, in my opinion, from some distortion control.

The tall thin problem

And the solution.

Upright!

So, fear not Distortion City, even if you are packing a P&S. Just plan to spend some quality time with PhotoShop Elements, or PhotoShop itself, and the Camera Distortion filter. It is amazingly easy.

This entry was posted in distortion, editing, instruction, perspective, PhotoShop Elements, postprocessing. Bookmark the permalink.

6 Responses to Distortion City! (and how to cure it…)

  1. forkboy says:

    Fascinating subject. And good to know this within Elements as that is what I use. I’ll have to file this information away for when I might need it.

    And regarding the philosophical implications….I think anything that can help make the picture look more like reality is a good thing. Unless, of course, your intent was for a distorted image of reality.

  2. rbpeirce says:

    If your camera is supported, DxO Optics Pro will take care of camera/lens distortion automatically. While you are at it, you can also correct perspective.

  3. I don’t see that much difference b etween start and finish to justify all the work you must do in between.

    • singraham says:

      Hi Joe,

      “All” that work needs to be put in perspective. Counting the time for Lightroom to make the copy image, the total time investment is less than 5 minutes.

  4. rbpeirce says:

    I see considerable difference. It is well worth correcting, but I wouldn’t do it that way.

  5. Pingback: Netbooks for the Traveling Photographer: take two « Cloudy Days and Netbook Nights

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