[MF3D.FORUM:570] Re: exact fl match for paired lenses

["Bill Glickman" <bglick@xxxxxxxx>]

Alan

       THANK YOU!   Everything you wrote perfectly jives with my experience.
I am in total agreement.... my problems were all violating the taking stereo
base!  And when this happens, there is no fix!  When I mount images at 2.5"
infinity separation (I assume this means the furthest item in the scene,
even if it's 30ft, right?) the chromes look great.

      I have  made a chart that shows at each near distance, what the far
distances can be to accommodate my 6.5" interocular minimum and my 22"
maximum.   I tested a few shots and they worked very well...  But now I will
blow another roll of 120 in each camera by not violating this chart and then
mounting them as Alan describes to see if they all work...

      I did have a few shots that did not violate anything that still would
not look right... but I guess this just boils down to other variables, like
cameras not level, one shot more blurred... etc.... I guess you can't expect
perfection with every shot, but sure would be nice to figure out what went
wrong so we do not reproduce the same error... anyway, I think I am on the
right track... will report back my findings!

Regards
Bill G




----- Original Message -----
From: "Alan Lewis" <3-d@xxxxxxxx>
To: "Medium Format 3D Photography" <MF3D.Forum@xxxxxxxxxxxxx>
Sent: Thursday, May 25, 2000 4:29 AM
Subject: [MF3D.FORUM:563] Re: exact fl match for paired lenses


> This post apparently was lost in transmission:
>
> Bill Glickman wrote:
>  The results were poor.  When I
> > mounted the chromes I learned why this practice is risky... you can not
> > prevent double vision on the side edges.  Although I must admit the
center
> > looks awesome.  But the whole effect is destroyed by the double vision
on
> > the edges.    I assume this is simply the consequence of having a base
wider
> > than it should be..
>
> Others have guided you in the right direction about setting the window
> when mounting.  But let me suggest that you use a standardized mounting
> procedure to automatically fix the problem forever (or at least verify
> where your problem area is).
>
> First, you should always mount the images with the infinity separation
> at 2.5" apart.  Ignore the mount window at this time.  The viewer you
> are using was designed for a 2.5" infinity separation, and if you always
> mount to this distance then every slide you view will be focused
> properly and be comfortable to view.
>
> Second, while keeping this distance set you can shift the pair in any
> direction you want while looking through the mount window (this is where
> you use the mount).  This is when you can set the composition for
> viewing.  The width of your images will dictate just how much in either
> direction you can shift the pair before overlapping the mount window.
> Just keep the infinity separation between the images at 2.5".
>
> I believe if you start using this method you will have more comfortable
> viewing.  It is possible that if you have an object too close to the
> camera for the lens spacing then you will still have a near point window
> violation, and this teaches you how to compose your images to eliminate
> this.
>
> If you can't shift the images in either direction without overlapping
> the window then it may be telling you that your cameras are too far
> apart for the image size on the film.
>
> While there are exceptions to this procedure, it will work in the
> majority of cases, and will teach you by experience how to set up you
> cameras for proper viewing effect.
>
> If you follow this 2.5" separation procedure then you will be able to
> determine easily why the image doesn't look right when viewed, and what
> you have to do to fix it.
>
>
> --
> Alan Lewis
> mailto:3-d@xxxxxxxx
> http://members.home.net/3-d
> Serious viewers for Serious viewer's
> New stereo viewers & Stereo Wedding Photography
>