re: focal lengths

[P3D Larry Berlin <lberlin@xxxxxxxxx>]

>>Ray Hannisian>If using a higher focal length simulates
>being closer to an object, should 'zooming in' require an
>increase in the distance between the cameras (to simulate
>the 'line of sight' angles for a person actually standing
>closer to the subject)?

Yes, adjust the stereo base (distance between cameras)  to obtain the
equivalent separation angle based on how close the object appears on film
and how much parallax is wanted. Is there a *right* term for this angle?

>Dave Worrell writes:
> Realistically
>200mm is "short" for wildlife photography 500mm is average
>and the "pros" range up to 1000mm ... (I got major "lens
>envy" over a couple Leicas with 1000mm lenses last year at
>Katmai, the bear place.)

It would seem that stereo base is quite dependent on the effective lens
length. 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. You would
also hope there aren't any nearby trees to ruin the shot. 

Relating the term *hyper-stereo* to a greater than normal stereo-base of
65mm only works for fairly normal lenses and subject distances. Calling a
telephoto shot with a wide separation a *hyper-stereo* shot leaves a lot
unsaid. Wouldn't it be more accurate to relate the term *hyper-stereo* to
shots with a wider than normal separation angle instead of stereo base?

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? Some
places (on the web) suggest the use of compressed air to synchronize the
shutters but that could be somewhat difficult under some conditions.

Larry Berlin

Email: lberlin@xxxxxxxxx
http://www.sonic.net/~lberlin/


------------------------------