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

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

These terms have been confused long enough.  True beamsplitters have been
used in stereophotography long before holography was even invented.  Let's
call image splitters "image splitters", and beamsplitters "beamsplitters".
That way no one, whether they are a stereographer or not, will have any
doubt that we are discussing two very different things.

JR

----- Original Message -----
From: "Ron Beck" <rbeck@xxxxxxxx>
To: <photo-3d@xxxxxxxxxxx>
Sent: Tuesday, January 09, 2001 11:21 AM
Subject: Re: [photo-3d] Are beamsplitters crappy?


> Yes, technically speaking, Pentax made an "image splitter".  Actually,
> Pentax made a device which took two different views and, via mirrors,
> transferred a "right" and a "left" image to a single frame on an SLR
> camera.  In common nomenclature, this is referred to as a "beam
> splitter" although "image splitter" is more accurate.
>
> True "beam splitters" are normally used for holography and are designed
> to "split" a laser beam into two distinctlight paths.  This is done by
> using a partially mirrored prism.  As mentioned below, part of the light
> is reflected, part of the light is transmitted through and part is lost.
>
> However, also as noted in other posts, the two terms are often
> interchanged when speaking of stereophotography.  Both terms normally
> refer to a mirrored device that will produce a left and right image on a
> single frame in a 35mm camera.
>
> So, please, unless holography is part of the discussion, assume that the
> device in question when "beam splitter" is mentioned is a mirrored
> device that produces a left and right image on a single 35mm film frame.
>
>
>
> "John A. Rupkalvis" wrote:
> >
> > 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
> > >
> > >
> > >
> > >
>
>
>
>