Re: [photo-3d] Re: Newbie question-near point distance

["John A. Rupkalvis" <stereoscope@xxxxxxxxxxxxx>]

----- Original Message -----
From: "Linda Nygren" <lnygren@xxxxxxx>
To: <photo-3d@xxxxxxxxxxxxxxx>
Sent: Friday, April 27, 2001 7:09 AM
Subject: Re: [photo-3d] Re: Newbie question-near point distance


> It seems that increasing camera separation
> roughly proportionally to the increased focal length (a little less
> usually, in practice) seems to avoid introducing the apparent size
> distortion that would otherwise occur with hyper stereo.

This is quite correct.  Theoretically doubling the focal length should mean
that the best result would be with double the stereo base.  In actual
practice, the perspective foreshortening that this effects makes a slightly
less increase in separation yield an even more believable result.

Very little stereo photography is true orthostereo.  Yet the human mind
compensates remarkably well as long as the distortions are within a range
that is "believable".  If whatever you are doing results in images that look
good, you should continue doing it.

> Yes, distortion of perspective can occur but this
> has not been a noticable problem for me so far. -Linda

Good!   You are probably very observant of backgrounds when you shoot, and
are careful to choose your POV such that nothing that will appear unnatural
is in the final images.  For example, if there is a tree in the background,
no one knows in a flat picture if it is a small tree close behind the
subject, or a large tree farther away.  In stereo, you think you know
because your brain analyzes the amount of depth that should be there
according to the amount of parallax.  But, if the focal length to stereo
base are inconsistent, you could be wrong.  Yet, if the picture looks good,
does it really matter?

JR


 

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