[MF3D.FORUM:1165] Re: Camera design

["Bill Glickman" <bglick@xxxxxxxx>]

Greg

       If you are looking for a camera that is handheld, than scratch this
idea...but if you want one that is tripod mountable only......my idea was to
us an inexpensive view camera, the rail type... mount two LF lenses which
would provide huge image circles for tilt, rise etc.   You can either link
the shutters together with a dual cable release or a solenoid operation.

     The beauty as I see it would be you can maintain about 70mm lens
separation,  possibly you can find some lenses that will allow for 65mm?
Then use a roll film back that you must alter the opening to 13cm...    You
would not need to alter the gearing of the back if you select a 6x7 back,
since two cranks would give you the desired 14cm per frame....so you would
get two 6x6.5cm shots plus 1 cm to separate the pairs.  10 pairs per roll of
220!    You would be assured perfect gg and film alignment since the makers
all use the same international standard for gg / film alignment.

       You would have very simple and fast ground glass focussing, which is
the ultimate..and also you would have the ability to have several lens
boards with any fl lenses you want.  You never have to worry about focus
distances or tilt etc. since gg focusing will show both images...with a mask
on the back of the gg of course.  You can get the lens maker to ship the
lenses to you in exact fl pairs.

       The Toyo lens boards are 110mm square, enough to mount 2 LF lenses.
LF lenses are reasonable inexpensive compared to good MF lenses also... You
can buy a new Toyo LF 4x5 view camera for about $500 if I remember..... best
to buy in the UK, much cheaper.  Plus you could now stop down to f45!   But
tilt will likely solve that and you would find yourself shooting much wider.

       You would also need a lens separation inside the bellows.  Between
the lenses you would need a bellows type separator to accommodate for
different distances between the front and rear standard.... These cameras
fold up pretty small, specially if you use a very short rail....or better
yet, have one rail for each set of lenses...

      If this interest you, let me know, you can make two, one for me also!
Maybe others might be interested in such a camera?  sure would overcome a
lot of shortcomings of today's MF cameras..... lens tilt, rise, gg
focussing, interchangeable lenses, focus at any distance, use different film
for different shots (with two backs) very high end modern, multicoated
optics,  The only downside would be its not handholdable....

     Camera is about $600 to be safe, $1800 (about half this if used) for
both 75mm lenses, $350 roll film back... few hundred for other supplies and
then your labor...so about $3k total... a bit more than a
Rolleidoscope...and this camera would be way more flexible than the Dr.
Gilde MF stereo camera which cost $13k for a lesser version!   To me, this
would be the ultimate MF stereo camera for landscapes... for people shots
the lenses would be a bit slow but still very feasible....

Bill G



----- Original Message -----
From: "Greg Erker" <erker@xxxxxxxxxxxxxx>
To: "Medium Format 3D Photography" <MF3D.Forum@xxxxxxxxxxxxx>
Sent: Friday, August 25, 2000 10:02 AM
Subject: [MF3D.FORUM:1154] Camera design


>   Now that my SR225 (twin TLR) is 99.5% working
> my engineering mind is planning my next better
> MF stereo camera. I ran some of these ideas past
> Sam on our day trip to the mountains but maybe
> someone here would like to comment also.
>
>   My goal with the SR225 was to get more shutter
> speeds, better viewfinder, better lenses and f32
> (compared to my Sputnik). I managed to get everything
> I wanted plus a few bonuses like crank wind/ auto
> shutter cocking etc.  I do have to set the apertures
> separately but I suspect they could be linked if
> I tried hard enough.
>
>   My next camera should fix two problems I currently
> face: It's hard to get everything in focus in MF
> (due to 80mm lenses) without shooting at f32 all the
> time. Secondly my SR225's mechanincal shutter speeds
> are consistent but not super accurate. So I have
> a cheat sheet on the back of the camera and have
> to stop down or open up various amounts (1/3 or 2/3's
> usually) for various speeds compared to the meter
> reading.
>
>   To solve problem 1 I'd like to make a camera with
> the finder lens in between the taking lenses like
> on a Rolleidoscope. I'd build the camera to have the
> ability to do lensboard tilt which would let me
> control where the plane of focus is. Often just the
> ground in the foreground is the near object so
> a degree or three of lens board tilt should allow
> you to bring it into focus along with infinity.
>
>   I've long thought that Mamiya TLR lenses would
> be ideal for making a MF stereo camera. They are
> readily available, high quality and come in a
> range of FLs. So a bellows focusing camera could
> have interchangable lensplates to go from 55mm to
> 75mm up to 180mm (I think).
>
>   I have heard that Mamiya used the same elements
> for the finder lens and for the taking lens. So
> perhaps getting a matched pair for left and right
> would be as simple as using the top and bottom lenses
> (on two different shutters). Getting a matched finder
> lens would still require some work.
>
>   Another idea I have is to use a dead shutter for
> the finder lens (shutter blades removed) and then
> have the ability to preview depth of field using
> the aperture control.
>
>   To solve the shutter speed linking and speed
> accuracy problem I wondering about using modern
> 35mm electromechanical vertical travel focal plane
> shutters. I believe the two curtains are tripped
> with separate solenoids. So an electronics guy like
> me could easily come up with a timing circuit
> (with 1/2 stop speed steps from 30s to 1/2000s) to
> trip the two in perfect sync and near-perfect
> accuracy.
>
>   The focal plane shutters would be used behind
> the lenses (assuming their diameter isn't too
> large).  There are some concerns about light leaking
> thru the FP shutter between shots (the new Cosina/
> Voigtlander rangefinder camera has an extra shutter
> curtain to prevent this). But I have some ideas
> about that.
>
>   Assuming I used FP shutters then the Mamiya lenses
> could all come from dead shuttered ones as long as
> the aperture controls work.
>
>   There is also the question of whether the Mamiya
> lenses have a large enough image circle to allow
> a useful amount of lensboard tilt.
>
>   Also fitting three lenses in a row might require
> a fairly large stereo base. With horizontal film
> travel that might mean 5 stereo pairs per 120 roll
> rather than the Sputnik's 6. Or I could go with
> two vertical travel rolls like my SR225.
>
>   Comments and ideas appreciated.
>
> Greg E.
>