P3D Re: Aerial stereo questions

[Robert Thorpe <thorpe@xxxxxxxx>]

Paul,

I shot aerial photos from helicoptors for 12 or 13 years. The rules
are pretty simple. Shoot at the highest shutter speed you can and 
keep your focus at infinity. You can shoot wide open if you like
(within the performance perameters of your lenses) because depth
of field in of no concern, you will be a thousand feet from the 
closest object. Take special care to avoid rotational errors. You
can play with tilting the horizon ala a banking turn, but I have
always found that a level horizon is the most satisfying. Frame the
object of interest exactly the same in both shots. This would 
normally result in keystoning in regular shots, but remember, you
are effectively shooting at infinity, which would mean the centerlines
of your shots are parallel. Besides, by framing on
the main object, you will be less likely to have to correct for
up-and-down and left-and-right displacement during mounting.
See if you can get the pilot to take the door off. Shooting thru
perspex almost guarantees bad shots.

Being in a helicoptor will make little difference in the way you
shoot your pictures. Most of the difficulties will be the usual
ones of proper exposure etc and they are the same on the ground 
or in the air. You hint at using higher speed film. Do you want
the pictures to look like daylight shots? I have alway preferred
night shots to be jet black between specular highlights. I guess
if there was a large illuminated area, say a sports stadium or
the Lincoln Memorial, I would do some trial metering on the 
ground to see what my settings would be.

======================
Robert Thorpe
Cedar Rapids, IA
thorpe@xxxxxxxx
http://www.skep.com


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