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

[Linda Nygren <lnygren@xxxxxxx>]

What is "PePax"?

My practice is to increase lens separation when using a longer focal
length (with more image  magnification) lens, which seems to work for
me. I am speaking of using 135 mm lenses on a couple of OM-1's. Although
in my case the photographic subjects (wildlife) are fairly distant, so
another relevant variable may be the distance between camera and
subject, and this may not work well with shooting close subjects with a
longer focal length lens. 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. Or putting it
another way, if your dual rig setup limits you to a hyperstereo lens
separation, using a longer focal length lenses with more image
magnification seems to mostly compensate so your reulting image does not
look like a miniature. Yes, distortion of perspective can occur but this
has not been a noticable problem for me so far. -Linda

Bruce Springsteen wrote:
> 
> George T. reported advice from David Lee as:
> 
> > - When using wide angle lenses double the separation.
> > When using long lenses cut the separation in half.  Normal
> > is 35mm or 50mm for 35mm film. Wide lens would be 28mm
> > or 24mm.  Long lens would be 100 or 135mm."
> 
> Mike Davis advised:
> 
> > "New base = Original base * (Original Focal Length / New Focal Length)"
> 
> Both are recommendations to reduce base when increasing focal length, or
> add base when subtracting focal length.  This is just the opposite of the
> old PePax rule of increasing (or decreasing) base and focal length
> together.  Though based on a fallacy suggesting that parallax and
> perspective are reciprocal parts of orthostereo, PePax still served the
> useful purpose of counteracting unpleasant "stretch" and "squeeze"
> effects.  What purpose does the opposite advice serve?
> 
> A perpetual newbie. ;-)
> 
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