Re: offset/stereo base, etc.

["The Photo-3D List" <photo-3d@xxxxxxxxxxxxxxx>]

> 1.   is the formula (mutilated by my reader--the awful 'elm' of UNIXland)
> 
> bO =  d * ( [ (an*af)/(af-an) ]*[ 1/f-1/a) ] )

Yes, that's it.

> 2.  i extrapolate that the proper max deviation in my view camera
> work should be 4 or 5 mm. Is this correct?  

I should have said it's lens length over 30.  
127 mm lens?  Then 127/30 = 4.2 mm.  So 4 or 5 mm would be fine.

> 3.  Should i shoot the first shot with the front shifted b0/2 to the left,
> [...]

Just remember the lens' displacement is less than the film's displacement.
So shift the whole camera to the left and then shift the lens to the right.
Then shift the whole camera right and shift the lens left.  The total lens
displacement should be 65 mm if that doesn't work out to be too much to 
handle according to the above formula.  You want the stereo window closer  
than your closest object, in general.  Let's say your closest object is at 
2100 mm and we want the window set at 2000 mmm.  Let's say the lens is 
focussed at infinity so it's operating at 127 mm from the film.  Then: 
(2127/2000)(65) = 69.1 mm
This is 4 mm more than 65 mm so you offset the lens 2 mm right and then 
2 mm left for the left and right shots respectively. 

If you're having trouble with this, think of projecting the outlines of 
the film apertures out into space.  Where they coincide is where the stereo 
window lies.

> 4.  Re: the Macromax loupe(s).  I accept your calculation of 62mm.  I had
> intended to use this (assuming i am ever nuts enough to spend that much
> money on a steal the light viewer) device for full frame work in 35mm
> format (25mmx36mm).  I would be using a normal lens of 55mm (micro Nikkor) or
> perhaps some day a 60mm Micro-Nikkor.  Does this ameliorate the problem
> with "35mm lenses"--ie, 35mm = format? or focal length?  I had thought
> that the ideal viewer lens is near the focal length of the taking lens. 

You just keep thinking that.  8-)
Yes, by "35 mm lenses" I meant 35 mm focal length lenses such as are found 
on miniature format (aka 35 mm format) stereo cameras.  I think 62 mm viewing 
lenses ought to be fine with your 55 mm taking lens.

> Does anyone have a copy of Ferwarda (sp?) they are tired of and want to 
> sell reasonably?  Is it still available from A Photographer's Place?  Is 
> it still in print? Is it understandable by the calculus challenged?

It's sold by some outfit in Holland.  The real challenge is not the math
but the English.  It needs editting.  Still, it's the best in the field.
Sellers of 3D stuff are named in Tim Klein's products and services list
which is on bobcat.  Look in there for the address of the bookseller.

> Thanks very much john, for your help.  If you have too much time on your 
> hands we could try exchanging Visio diagrams by uuencoded e-mail.  I 
> haven't done it, but it seems to be a reasonable way to go about drawing 
> pictures of this stuff.

There are some GIF images in the technical directory in bobcat which may help.

John B



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