[MF3D.FORUM:1157] Re: Camera design

[Greg Erker <erker@xxxxxxxxxxxxxx>]

>Quick calculations say that the min. stereo base with the finder lens
>right inbetween the taking lenses is 4.4".

  Yuck. My current 88mm on my SR225 is near the
maximum I'd want.

  Perhaps a different finder lens (say a Ricohflex
or diacord one) would work but be smaller.
Could save a 1/2" perhaps on the base. Still
that would be close to 100mm.


>I'm not following exactly here.  But the easiest way is to just buy two
>complete lenses and throw away (!) the extra finder lens.
>The Mamiya TLR is a professional camera, and the finder lens/taking lens
>lenses are well matched for professional use.  I have never heard anyone
>complain about these camera systems having focus problems.  I think they
>have stood the test of time very well.

  I tested five Ricoh Rikenon lenses to get
a decent (<0.5%) match so I was thinking
if Mamiya matched taking lens and finder
lens FLs (and the finder can be used as
a taking lens) someone has already done the
work for me.

  But if you want to use the finder for
critical focusing (indoors at f8, say)
then it must match the taking FL pretty
well also. So I'd likely still have
to go thru a bunch of Mamiya lenses to
get a taking/finder/taking set that matches
well.

>They must have
>controlled the camera body dimensions very tightly.
>
>I put the shims back in and infinity focus was good for both lenses.

  Interesting.

  The Diacords and 225's I've taken apart seem
to be the same. They have different thicknesses
of shims which I assume is to bring the taking
lens into proper infinity focus. I assume the
milled the film rails and the face the shutter
mounts against to very tight tolerances.


>Are we at the point of technology in shutter design yet to use the LCD
>screens that can change density with differing voltage?  It sure would
>be nice if this technology could be applied to shutters.

  The problem is that an "on" LCD shutter would
still only pass 40% of the light. And it would
polarize all of your photos which might be good
or bad I suppose.

  Also the off setting likely would still let
maybe 1% of the light thru (like crossed polarizers)
so you'd still need something mechanical to
prevent film fogging.

>Your description above of the shutter sounds similar to the electronic
>shutter used in the Polaroid Color Pack cameras.  Lots of electronics
>packed in those Polaroid shutter boxes.

  Those are auto exposure cameras with a
light sensor and an integrater circuit
aren't they?

  Being a digital guy I'd just make a
counter circuit that would delay from
0.5ms (and 0.71 ms for those 1/2 stop
steps) down to 30s in multiples of 2.
IE/ .5, 1, 2, 4, 8, 16, 32, 64, 128,
256, 512, 1024... to 32768 ms. Easy :)

Thanks for the comments and info - Greg