Re: Camera shift spacing

[P3D john bercovitz <bercov@xxxxxxxxxxx>]

Crazy David Kesner writes:
> wouldn't it be possible to mark your viewfinder (or prism or mirror)
> with two parallel lines once you have figured out the proper spacing?
> Then all you would have to do is make sure that the nearest object in
> the frame doesn't exceed that spacing. It wouldn't matter whether you
> were shooting insects (hypostereo) or the Grand Canyon (hyperstereo).
> Is this just too simple or am I just crazy?
 
Cool idea!  You'd need a real image in there someplace of course so that
there'd be a place to put the line.  SLRs have real images at the ground
glass and I imagine there are non-reversed-Galilean viewfinders around.
If not, it would be easy enough to make one.
 
The reason this idea is so good is that it previews on-film-deviation
which is what you are really trying to hold to a viewable limit.  The
viewable limit is about one part in 30, angularly speaking.  So if you 
have an SLR with a 50 mm lens on the front, take the ground glass out
and on the bottom of it put two lines which are 50/30 = 1.7 mm apart.
Now follow David's instructions and Bob's your uncle.  If your viewfinder
has a different focal length than your photographic objective, just take
1/30 of the _viewfinder_ lens' focal length at its image plane to figure
the line spacing.  Great invention.  Why don't you market a viewfinder 
which fits in the strobe shoe?  You could offer inserts with the lines 
on them.  One insert for 35 mm lens, one for 50 mm lens, and so on.  The
SLR ground glass marking would be a little better for closeups because 
you rack the lens out for closeups thereby changing its operating focal
length.
 
John B


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