>From: "Lama-Jim L'Hommedieu" <lamadoo@xxxxxxxx>
>
>Is the "lens node" always one-half of the focal length away from the film
>plane?
In nodal-point calibration using MANY lenses, I have seen no pattern.
As I recall, the 24mm shift's nodal point was farther out than the 90/2!
I put a sticky label on my Kiwi pano head, and made calibration ticks for most
of the wides through near-teles that I have. I think the 90/2 was the longest
one that could be aligned on the Kiwi.
> > This is not a true panorama head, or at least a very limited one, as it
>> does not allow for placing the lens node over the rotation axis.
In my experience, nodal alignment gets more critical as the focal length gets
shorter. I did 13 shots with the 180/2.8 that covered about 90 degrees -- using
only the Bogen 3270 hear head, which is SERIOUSLY NOT nodal-aligned, in BOTH
directions!
<http://www.bytesmiths.com/Art_Gallery/image.php?by_ID=99AO08-18>
On the other hand, here's one done with the 24/3.5 shift, carefully
nodal-aligned on the Kiwi (you need QuickTime installed):
<http://www.bytesmiths.com/Art_Gallery/SilverFalls/index.html>
Finally, here is one done with the 21/3.5, again with the Bogen 3270. It took a
lot of tweaking, and still shows some serious irregularities where the frames
overlap. QuickTime Virtual Reality Authoring Toolkit did a great job of
compensating, though -- it shows up mainly as softness where the two images
didn't register, so it blended them. Notice in particular how the silo seems
"lumpy" and not perfectly round:
<http://www.bytesmiths.com/Art_Gallery/SiloPan.mov>
Bottom line: you can have a LOT of fun with this with inexpensive stuff, but if
you're going to spend money on it, get a "real" pano head capable of nodal
alignment. I believe the Kiwi can be had for as little as $150 or so.
--
: Jan Steinman -- nature Transography(TM): <http://www.Bytesmiths.com>
: Bytesmiths -- artists' services: <http://www.Bytesmiths.com/Services>
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