Re: [photo-3d] Are beamsplitters crappy?

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

What are you guys talking about?   To my knowledge, Pentax never made a
beamsplitter.  They did make some image splitters that split the image into
two, narrow side-by-side images.  But a beamsplitter doesn't do that.  As I
have explained many times, a beamsplitter requires two cameras at 90 degrees
from each other and 45 degrees incident to the surface for stereoscopic
photography.

A beamsplitter permits full size (full width and full height) images.  Good
quality beamsplitters are AR coated, and transmit about 48% of the light and
reflect about the same (depending upon the efficiency, around 4% of the
light is lost in absorption).

JR

----- Original Message -----
From: "Mike Kersenbrock" <michaelk@xxxxxxxxxxxx>
To: <photo-3d@xxxxxxxxxxx>
Sent: Tuesday, January 09, 2001 2:12 AM
Subject: Re: [photo-3d] Are beamsplitters crappy?


> Bryan Mumford wrote:
> >
> > Would
> > others agree that beam-split pairs are unsatisfactory?
>
> Depends upon what one is using them for.  While I don't agree that
> they are crappy, I do agree that they have significant restrictions
> in their use, or at least my Pentax one does.
>
> > about it this way before, but I'm getting four times as much picture
> > data in two full frame cha-chas than I would get in a single frame
> > split image. Maybe a beamsplitter is not a worthwhile project after
> > all.
>
> In terms of amount of film you get exposed, quite true. But a
> "beamsplitter" (image splitter) can take the two images at
> the same time (and with perhaps a 1/4000 sec shutter if light is
> bright enough) -- something a cha-cha has no hope of achieving.
> "Beamsplitter" also probably would provide better rotational
> alignment between the two images (one thing I certainly never
> seemed to be able to do too well when cha-cha'ing with my wife's
> digital camera).  :-)
>
> I'd call it a step up from cha-cha's, but most any stereo camera would
> be a step up from the beamsplitter (except only for some special niche
> circumstances).
>
>
> Mike K.
>
>
> P.S. - When I was married mumble years ago, I had a friend use my Pentax
>        stereo adapter, and his photos are loved by us more than the ones
done
>        by the professional (and not just because it was 3D, the image
content
>        was important too :-).
>
> >
> > Bryan Mumford
> > Santa Barbara, California
> > http://www.bmumford.com
>
>
>
>