Focal length

[P3D Section of Epidemiology <dworrell@xxxxxxxxxxxxxxxxxxx>]

>Larry Berlin>Using a 1000mm lens gets you close to the
bear but you would need quite a large stereo base to get an
equivalent up-close parallax. <snip> This brings up the
question of how to synchronize two cameras set up at a
significant distance from each other to capture such a
shot. Say the bear is fishing in a river and will stay
there long enough to set both cameras and have them framed
on the action, perhaps with the help of an assistant. Is
there a radio-controlled device available to trigger the
cameras?

The crux of the biscuit is exactly how much separation
would be necessary. In the bear example above (at Katmai)
the viewing platform is roughly 150 feet (50 meters) from
the center of the falls (the best fishing spot) where the
biggest bears are. As I can't afford matched 1000mm Nikkors
:-( something in the 200mm range is more reasonable as I
already have one (I'm assuming zooms are out due to
difficulty exactly matching focal length). Under these
conditions I doubt I'd need more than several extra mm of
separation. Perhaps some sort of calibration marks could be
placed on the twin bar indicating separation for various
distances. For example: 61mm at 10ft, 62 at 20 etc.  Have
any of you bar users made such calculations? Has anybody
tried something similar?

Dave Worrell
Publications Technician
State of Alaska
Section of Epidemiology


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