[tech-3d] Re: Stereo base calculations

["Michael K. Davis" <zilch0@xxxxxxxxxxxx>]

Hi Don,

>    Date: Mon, 4 Dec 2000 21:16:06 -0800
>    From: "Don Lopp" <dlopp@xxxxxxxxxxxxxxx>
> Subject: Re: Digest Number 41
>
> Mike thank you for taking the time to check me out Could you tell me what
> the numbers would be for-- 


>75mm lens  for 75 feet to  with a i foot base,

I'll assume you omitted 3000 feet as the far.  The deviation would be 0.98mm.



> 100mmlens 100 feet to 3000 feet , one foot base

The deviation would be 0.97mm.



> and finally 135 mm lens - 135 feet to 3000ft with a one foot base ?

The deviation would be 0.96mm.

Interesting!  I realize now, that in my last response to you, when I was
comparing the percent of MAOFD produced by each of these combinations, I
had incorrectly concluded that your OFD shrinks a lot as you increase focal
length, but it's really very close to being constant - at right under 1mm -
which is exactly what you had said originally!  I have to hand it to you
for really knowing what your method is producing on film.

Summarizing:
  
39.1 % of MAOFD for a  75mm lens = 0.98mm OFD when Near =  75 feet, Far = 3000
29.1 % of MAOFD for a 100mm lens = 0.97mm OFD when Near = 100 feet, Far = 3000
21.3 % of MAOFD for a 135mm lens = 0.96mm OFD when Near = 135 feet, Far =
3000 


> I realize that my symplistic plan would be worthless for close in stereo
> such as when they tried to shoot stereo of tSports Illustrated models last
> summer although common sense should have indicated  that itcould not be
done
> the way they attempted to do it allthough your system woul have indicated
> whether there was a way they could do it . They were partially saved by
> having some RBT 35mm cameras available though in my opinion the show
> presented in Phoenix was , in my opinion,one of the lousiest 3D shows I
have
> ever seen at a NSA convention ( I am referring to the technical aspects of
> the program -mostly too hyper). You are correct in assuming that I fine
tune
> my stereo base numbers based on previous experience such as any foreground
> verticles or lack of foreground verticles or when verticles are only on
> outer edges not in center( I believe that central verticles are not
usefull
> in my pictures- though not allways possible to avoid). A

How exactly to you respond to the presence of foreground verticles?  Do you
reduce base or increase it?   Can you explain why you handle the presence
of foreground verticles differently?  Is it just aesthetics?

Thanks!

Mike Davis



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