[MF3D.FORUM:918] Re: Black mount obsession?

[Richard Twichell <rmt@xxxxxxxxxxxxxxx>]

Bob Aldridge writes:
> I'm trying to put together a projection system for these mounts, and in 
> their current, white form, they are not opaque. Using black - or blackened - 
> board would help immensely in this respect...

I'm working on MF projection too and came to the conclusion that the
chips are too close together in the Spicer mounts for the optics of MF
projection.  Edmund recommends condensers 1 1/2 times the diagonal of
the chip.  All the suitable lenses I've tested are too large also to
center on the chips...The big Rolleis are way to big, and the Buhl
series 3 216mm f3.4 lenses, which are made for 35mm/superslides but have
just enough coverage for MF, are a bit too big, but too big
nevertheless.  

I should think black mounts would be a liability for projection if they
are entirely black due to heat absorbtion.  Ideally they should be black
on the lens side and white on the lamp side, like RBTs.  The white
reflects light back into the source, and the black reduces internal
reflection in the projection optics.

With the dimensional obstacles I abandoned single-mount projection and
opted for a 2 (or 4 for dissolve) machine setup.  At least that way
there is some standardization, with gepe mounts.  (Another issue there -
I've tried glassed and unglassed, and the focus uniformity is so much
better with glass that I've abandoned the economy and ease of mounting
(2 surfaces to clean instead of 6) of unglassed.

I'd be grateful to learn your conclusions about the optical dimensions
issue -

Dick Twichell