Belplasca close-up attachment

[P3D emdesher <emdesher@xxxxxxxxxxxxxxxxxxxx>]

On Wed, 8 Jan 1997, P3D Elliott Swanson wrote:

> 
> Eric G. says:
> 
> I have no personal experience with it, but have spoken with people who
> have used it. They have told me that:
> - As you point out, the attachment is rare and rediculously expensive.
> - The quality of the lenses is nothing special
> - As with Realist and other close up lenses, you are really shooting too
> close for the lens spacing of the camera
>  
> Elliott says:
> 
> The above is why I put the post out there. No need to go on a quest for
> the elusive Belplasca close-up adapter if a common VM close-up will
> deliver the same useful-tho-less-than-perfect results. However, keep in
> mind that the prismatic element in the VM close-up lens makes a toe-in
> correction to compensate for the lens spacing. I'd guess that the VM 36" 
> close-up unit also is making a +1 diopter correction, or thereabouts. So
> the cheap (relatively) VM way of making the adaptation, as opposed to
> paying big bucks for the Belplasca close-up unit, will allow one to get
> shots that would otherwise be unshootable. Still, there is going to be
> some image distortion due to the toe-in caused by the prism lenses. Just
> don't forget your rubber band to hold it on.  :) 
> 
> 
> 
There is some confusion here over the true purpose of the Belplasca 
close-up attachment (called the "Optical wedge attachment" in a 
promotional leafet.  The VM close-up lenses incorporate both magnifying 
power AND a wedge prism to produce a "toe-in" effect.  Because the 
Belplasca lenses have helical-type focusing, they are already capable 
of close in work down to one meter (3'4").  The problem with closeups 
arises only when you use the original Belca stereomount, since it was 
based on a fixed, pin-regristered system.  This long discontinued mount 
was only available in a normal aperture.  The idea was as long as your 
subject matter wasn't closer than 2.5 meters, the film pair could be 
mounted without any further adjustments.  What the attachment 
provided was a optical way to move the subjects together, or "toe in" 
effect.  It was then possible to use the Belca mount, without any need 
for adjustments or masking.  If you use a mount capable of horizontal 
film adjustment, a VM close-up set is not of much use.  If you want to 
get closer than one meter, supplementary close-up lenses on series 5 push 
down rings makes more sense and is much cheaper.  The real limit is as 
you get closer, when you try to mount the film pair there might be light 
gaps, and the depth range become too excessive unless you are very 
careful about shortening the background.  Dennis Sherwood, proud owner of 
a Belplasca.


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