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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