Yes, I also do distortion correction with PTLens before stitching panos.
Chuck Norcutt
Moose wrote:
> Nathan Wajsman wrote:
>> When I posted the golf course panorama the other day, many of you asked for
>> a larger size. So, here is one I made this afternoon at our beach. It covers
>> about 200 degrees. I took 15 pictures with the 35mm lens. Unfortunately I
>> did not level the tripod completely, so there is what appears to be some
>> barrel distortion.
>>
>
> I haven't looked at the full size image, so can't speak to any
> repetitive barrel distortion within individual parts. The overall
> distortion you see is sometimes called "cigar" distortion. Think about
> the optical/mechanical situation for a moment.
>
> As the angle varies from straight ahead, the focal distance increases
> and the image gets smaller. The effect is not particularly obvious with
> many subjects. With a small, even, linear band like the sea in this
> image, it becomes very obvious, appearing larger in the middle and
> tapering off in both directions.
>
> It's very common with panorama cameras using rotating lenses, like the
> Widelux, Horizant, etc., where the whole sweep is on one film image. It
> is much less commonly seen in stitched panoramas simply because most
> stitching software compensates for it in at least one mode.The stitched
> image gets taller as you go out from the middle. You then crop off the
> spreading wings at the height of the central frame.
>
> Linear distortion within individual frames is another issue that can
> indeed detract from the result. If I am doing a panorama at 35 mm focal
> length, I use the long end of my 17-35, which is almost distortion free,
> rather than the short end of the 28-300, which has modest visible
> distortion @ 35 mm.
> <http://galleries.moosemystic.net/MooseFoto/index.php?gallery=Miscellaneous&image=MossBraeP116laz.jpg>
>
>
>
> Even modest distortion can cause problems matching across frames. Taking
> many, highly overlapping frames, as you did with the golf course, gives
> the stitching program a way around such problems. Correcting each frame
> with something like PTLens or DXO before stitching also works quite
> well, in my experience.
>
> Moose
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