Re: Stepped out pano


"Mark Thomas" <markt@_don't_spam_marktphoto.com> wrote in message
news:gju2jo$kuu$1@xxxxxxxxxxxxxxxxxxxxxxxx
Dudley Hanks wrote:
Thanks for the info, Mark. I have two pano stitching progs on my system,
the Canon pano stitching utility which comes bundled with the EOS
utilities, and Adobe Photoshop Elements. I also have another program I
haven't tried yet, it's called PhotoExplosion, or something like that. I
haven't used it yet, so I'm not sure what it does, but will check it out
one of these days.

Good luck, Dudley - let us know how you go. There are three major
problems with the cheaper panorama programs:
First is their ability to adjust differences in exposure/colour between
frames - a good program will adjust the individual images *before* they do
the stitch, *including* things like vignetting. Naturally you should
always shoot the images in manual mode so the focus and exposure remains
constant. But vignetting, use of polarisers, or even slight variations in
light (eg cloud movement) can provide variations that mean the joins stand
out like pupnuts in lesser programs!

Secondly, the cheaper programs will encounter difficulties with
distortions and even slight mismatches. No lens is perfectly linear and
the wider you shoot your originals, the more the images will need
'stretching' to get things to match, esp at the outer edges of the images.
Hence the suggestion of more images, taken from further back, but
obviously there are diminishing returns... Then there are real
perspective issues caused by the camera not being rotated about it's nodal
point (very rarely (ever?) is the tripod mount the true optical centre of
the camera), and objects that may move between frames. There are plugins
for some of the programs (Eg PTGUI has Smartblend/Enblend) that can help
with these issues.

Lastly, they may have memory limitations that prevent them creating very
large (pixel-wise) panoramas.

Like you, I love the challenge even more than the result - I have many
panoramas in progress.. and like to share experiences with similar minded
lunatics. (O:

Cheers, Dudley.

Ah, more stuff to consider...

I'm guessing that the non-centered tripod bolt will produce greater problems
at a longer focal length? Whereas, problems stitching distorted corner
areas will plague the lower focal lengths? So, the "sweet spot" of a lens
is going to be where the benefits of one does not magnify the problem of the
other...

For my first try, I'll probably use the old 28 - 80mm lens that came stock
on my old A2. It had decent optics, and might yield an acceptable tradeoff
in it's midrange, which should be roughly equiv to 75 or 80mm (35mm equiv).
I'm guessing that, since I'll be working on a 90 degree corner, a longer
lens would necessitate moving back too far from the corner to keep the
straight-on line of sight down each street at the outside edges, which is
what I think will help to set off the houses / trees in the center.

This could be interesting...

Thanks, again, Mark.

Take Care,
Dudley


.

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