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About Subject: Mamiya 55mm Wide-Angle Focusing Lens ProjectDate: 2008-02-28 19:24:13From: Peter Thomson
Hi all. I have completed the design and measurement stage for a
focusable wide-angle lens set. Before I get into it I must say that I
agree with Sam about the quality of the Mamiya lenses and the degree
of quality that the company achieved. I bought three lens sets and
initial trial matching photo shoots with the taking lenses still in
their mounts showed 2 of the 3 possible combinations were a match,
with one being very slightly better than the other. Further tests
with the viewing lens put into a taking lens body gave equally superb
results. One only has to note the use of shims as thin as 0.05mm
under either of the lenses to realize the degree of perfection they
were after. They would hardly bother shimming to that tolerance if
the focal length wasn't VERY close, as the shimming would only bring
alignment at one point! Moving along...............
Here is my KISS proposal. (Keep It Simple Stupid)
I am machining mounting blocks from the same material I used for the
trial shooting sessions, ie, a black industrial Nylon. It is called
Cast Nylon 6 MoS2, which has Molybdenum Disulphide added to give
excellent low friction/self lubricating properties. It is easily
machined (including without coolant) and is very tough. It is also
quite cheap. My supplier has it for $45 Aus (500mm x 65mm) See it
here http://www.rsaustralia.com/cgi-
bin/bv/rswww/searchBrowseAction.do?D=nylon%206%20stock%20&Nr=AND%
28avl%3aau%2csearchDiscon_au%3aN%29&Ntk=I18NAll&Nty=1&Ntt=nylon%206%
20stock%20&Dx=mode%20matchpartial&Ntx=mode%
20matchpartial&N=0&name=SiteStandard&forwardingPage=line&R=1935294&cal
lingPage=/jsp/search/search.jsp&BV_SessionID=@@@@0742364922.1204243187
@@@@&BV_EngineID=ccdfadedgkdkdfkcefeceeldgondhgm.0&cacheID=auie
I realised that the simplest answer was to utilize the lens's own
mounting thread (0.5mm pitch) as the focus adjustment means.
Normally, with such a fine thread this would be a no-no, but with the
Nylon MoS2 as the mating part, no worries mate! This makes the blocks
quite simple to machine, with the possible exception for some (me,
I'm only ), the thread, which will need precise machining.
An alternative to machining a thread is to have the barrel 0.1 -
0.15mm smaller than the thread diameter, and then let the lens thread
cut a thread when it is screwed in!
See them here........http://www.flickr.com/photos/14946872@N04/
Screws can be put in to mount the blocks on the lens plate by just
drilling a pilot hole and screwing it in. No need to tap them!
As seen in the first image, the shutter back has to be machined to
take the rear of the lens barrel, 33mm dia x 1.5mm deep. This is
easily done with a Dremel High Speed Cutter. Naturally, the rest of
the camera has to be covered with plastic and taped up with duct tape
to 100% protect it from shavings, and have someone hold a vacuum
nozzle close to suck it all away. The machined area has to be black
matt painted of course.
The lens bodies have to have the protuberances cut back to allow
rotation. The shutter cock and trip can be cut back to 2-2.5mm. The
shutter trip has to have a small hole drilled to take a locking pin
bent from a paper clip to permanently hold the lever in the trip
position. The shutter is of course left on B, and is quite difficult
to move out of B when the shutter trip is held on.
The lenses are screwed fully into their blocks, and the blocks then
mounted onto the lens plate with the aperture mark at the top for
ease of use. With the block thickness of 9.7mm, this gives focus at
approx. 30 meters. Screw the lenses out 1/2 turn gives 10 meters, one
full turn gives 8 meters, 1 1/2 turns gives 5 meters and 1 3/4 turns
gives 3 meters. (All approx.)
The rear part of the block which takes the rear lens barrel has to be
a close fit as this supports the lens and keeps it aligned taking the
burden off the lens thread. Making the blocks out of anything but the
recommended material would require grease lubrication on the thread
and rear barrel. You could of course screw the lenses out and add a
shim if you wanted to fix the focus at a particular setting, but I
don't really think this is necessary.
Any comments or questions?
Happy 3Ding, Peter
focusable wide-angle lens set. Before I get into it I must say that I
agree with Sam about the quality of the Mamiya lenses and the degree
of quality that the company achieved. I bought three lens sets and
initial trial matching photo shoots with the taking lenses still in
their mounts showed 2 of the 3 possible combinations were a match,
with one being very slightly better than the other. Further tests
with the viewing lens put into a taking lens body gave equally superb
results. One only has to note the use of shims as thin as 0.05mm
under either of the lenses to realize the degree of perfection they
were after. They would hardly bother shimming to that tolerance if
the focal length wasn't VERY close, as the shimming would only bring
alignment at one point! Moving along...............
Here is my KISS proposal. (Keep It Simple Stupid)
I am machining mounting blocks from the same material I used for the
trial shooting sessions, ie, a black industrial Nylon. It is called
Cast Nylon 6 MoS2, which has Molybdenum Disulphide added to give
excellent low friction/self lubricating properties. It is easily
machined (including without coolant) and is very tough. It is also
quite cheap. My supplier has it for $45 Aus (500mm x 65mm) See it
here http://www.rsaustralia.com/cgi-
bin/bv/rswww/searchBrowseAction.do?D=nylon%206%20stock%20&Nr=AND%
28avl%3aau%2csearchDiscon_au%3aN%29&Ntk=I18NAll&Nty=1&Ntt=nylon%206%
20stock%20&Dx=mode%20matchpartial&Ntx=mode%
20matchpartial&N=0&name=SiteStandard&forwardingPage=line&R=1935294&cal
lingPage=/jsp/search/search.jsp&BV_SessionID=@@@@0742364922.1204243187
@@@@&BV_EngineID=ccdfadedgkdkdfkcefeceeldgondhgm.0&cacheID=auie
I realised that the simplest answer was to utilize the lens's own
mounting thread (0.5mm pitch) as the focus adjustment means.
Normally, with such a fine thread this would be a no-no, but with the
Nylon MoS2 as the mating part, no worries mate! This makes the blocks
quite simple to machine, with the possible exception for some (me,
I'm only ), the thread, which will need precise machining.
An alternative to machining a thread is to have the barrel 0.1 -
0.15mm smaller than the thread diameter, and then let the lens thread
cut a thread when it is screwed in!
See them here........http://www.flickr.com/photos/14946872@N04/
Screws can be put in to mount the blocks on the lens plate by just
drilling a pilot hole and screwing it in. No need to tap them!
As seen in the first image, the shutter back has to be machined to
take the rear of the lens barrel, 33mm dia x 1.5mm deep. This is
easily done with a Dremel High Speed Cutter. Naturally, the rest of
the camera has to be covered with plastic and taped up with duct tape
to 100% protect it from shavings, and have someone hold a vacuum
nozzle close to suck it all away. The machined area has to be black
matt painted of course.
The lens bodies have to have the protuberances cut back to allow
rotation. The shutter cock and trip can be cut back to 2-2.5mm. The
shutter trip has to have a small hole drilled to take a locking pin
bent from a paper clip to permanently hold the lever in the trip
position. The shutter is of course left on B, and is quite difficult
to move out of B when the shutter trip is held on.
The lenses are screwed fully into their blocks, and the blocks then
mounted onto the lens plate with the aperture mark at the top for
ease of use. With the block thickness of 9.7mm, this gives focus at
approx. 30 meters. Screw the lenses out 1/2 turn gives 10 meters, one
full turn gives 8 meters, 1 1/2 turns gives 5 meters and 1 3/4 turns
gives 3 meters. (All approx.)
The rear part of the block which takes the rear lens barrel has to be
a close fit as this supports the lens and keeps it aligned taking the
burden off the lens thread. Making the blocks out of anything but the
recommended material would require grease lubrication on the thread
and rear barrel. You could of course screw the lenses out and add a
shim if you wanted to fix the focus at a particular setting, but I
don't really think this is necessary.
Any comments or questions?
Happy 3Ding, Peter