Correcting for Wide Angle Lens Distortion - PanoTools Plugin
Started by Peter Schulz ·
12Posts
12Replies
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Correcting for Wide Angle Lens Distortion - PanoTools Plugin
12 posts
Correcting for Wide Angle Lens Distortion - PanoTools Plugin
Wide angle pictures suffer from distortion. With a flat port you get pincushion distortion and with a dome port you get barrel distortion. And the wider the angle of coverage the more distortion you get.
Fortunately there is a software fix for this problem. It's called PanoTools. PanoTools plugins are available for Adobe PS, Adobe Elements, and Paint Shop And the plugins are free!
See the URL below for details and sample pics. Is this magic or what?
Excellent article! Would you consider submitting this for a Wetpixel Feature?
Sincerely,
James Wiseman
Dome ports don't cause barrel distortion though. The Inon dome on the Inon WAL appears to but that's because of the natural barrel curvature of the lens that you don't see when the front interface is water rather than air.
James Re "Excellent article! Would you consider submitting this for a Wetpixel Feature? "
Answer yes. What do you need from me other than my permission, which you have.
Craig Re "Dome ports don't cause barrel distortion though."
I know almost nothing about this whole subject. But what I do know is that it looks like barrel distortion and the negative correction numbers I used correct for barrel distortion. So if it walks like a duck and talks like a duck, isn't it a duck?
Peter,
If you could send me the text and captions in a Word document, and the photos as jpeg's in a separate email, I will put it online. Oh, and you permission of course - don't worry, you won't lose your copyright - just give us permission to publish it once on Wetpixel.
Cheers
James
Craig Re "Dome ports don't cause barrel distortion though."
I know almost nothing about this whole subject. But what I do know is that it looks like barrel distortion and the negative correction numbers I used correct for barrel distortion. So if it walks like a duck and talks like a duck, isn't it a duck?
Yes, your Inon dome produces classic fisheye barrel distortion. This is not a true generalization of domes though. Perhaps I'm being too anal! I might have said "wide angle adapters and fisheye lenses" rather than "dome port". I think it's fine, really.
I'm glad to see an article of this nature about this subject. We don't have to accept barrel and pincushion if we don't want to.
Craig Re "This is not a true generalization of domes though."
I suspect you are right, as the Ikelite 5060 WAL with a dome doesn't produce nearly as much distortion as my 5050 with an INON WAL and dome. For sample Ikelite pics see the following URL.
Perhaps a partial answer is that the Ikelite pics are at about 90 degrees and my INON pics are at about 127 degrees. And perhaps its not the domes but their implementation as you suggest. I'll ponder this some more and may change my wording.
The Inon WAL is designed to have a water interface on its outer lens element and still be rectalinear. When you add a dome, the index of refraction changes at that interface and the lens becomes much wider. The downside is significant barrel distortion. In this case it is not the dome itself that causes the distortion but the change in application of the lens. Really its just how you look at the problem. If you put a wide angle land lens behind a properly designed dome you won't get any additional barrel distorition beyond what the lens already has. That's what I'm trying to say. Nevertheless, the Inon is your application is a semifisheye and benefits from the corrections that you describe. Using a Sigma 15mm FE with a D100/S2 yields very similar results.
Panotools is great for things beyond simple pincushion/barrel as well. Here is page that provides panotools coefficients for a range of popular Nikon lenses.
All right, Peter's article has been posted on Wetpixel - thanks Peter! (now you all know what this loser behind the keyboard was doing last night).
Look in the Features.
Check out the turtle shot again and you can see that the sgt major in the upper right gets "stretched" by panotools. Sometimes it's acceptable and sometimes it's not. Peter's wreck shots are a PERFECT example of when a fisheye lens needs some "help." Everyone knows that the doorway on a ship is not shaped like a Tylenol! :-)
