p.16 #1 · lens repair, modification and disassembly guide thread
Max_Pain wrote:
..Derek's DIY site only had one article about a different (newer?) Sigma 15mm but it was in German and I had no idea what they were talking about, even after using Google Translate...
p.16 #2 · lens repair, modification and disassembly guide thread
Would you be able to post the 3D print file somewhere when ready? I think it's time for me to convert my G45. I actually wouldn't mind going in with others to order a set of rings, but I'm not sure if there is much demand or if they can still be made for small orders.
LightShow wrote:
The helicoid in the 55/1.7 is used to focus... I'm not sure what you mean... Unless you mean RF coupling.
AFAIK, Sebboh's engineering drawing for the G45 still requires a couple modifications, one is to add some thickness to the back edge to hide a gap when the lens is focused to MFD.
The other is to change the location of the screw holes that the LTM to M-mount adapter use to secure it to the rear ring, one of the holes lands on the 6bit location.
Hey Sebboh, do you mind if I get the transplant rings drawing converted to a 3D print format?...Show more →
p.16 #3 · lens repair, modification and disassembly guide thread
sebboh wrote:
i finally got around to converting my g90 to a proper helicoid, this time in e-mount rather than m-mount. figured i'd give a brief description of what i did.
i followed a similar method outlined by koji kawakami here, however i left the contax g helicoid intact rather than cutting off the bottom portion of the interior of the helicoid and i inserted the intact piece into a donor helicoid to be secured with set screws rather than an m39 to m42 adapter.
...for the donor helicoid i used a leica zooan helicoid, which can be found cheaply on ebay.
...the front of the zooan has a little ring on the front that pops off to reveal three set screws that hold the distance scale to the actual helicoid. i removed these set screws, drilled all the way through the helicoid in those holes. and tapped it for 0-80 screws to allow large set screws that will also hold the piece from the g90 in place:
I've bought a ZOOAN and intend to convert my G90 in the manner you've very usefully documented.
Would you be able to tell me please where you obtained a tap-set to tap the 0-80 holes at the top of the ZOAAN under the ring? I have been unable to source a suitable tap set here locally.
p.16 #4 · lens repair, modification and disassembly guide thread
lenticular11 wrote:
I've bought a ZOOAN and intend to convert my G90 in the manner you've very usefully documented.
Would you be able to tell me please where you obtained a tap-set to tap the 0-80 holes at the top of the ZOAAN under the ring? I have been unable to source a suitable tap set here locally.
TIA
David
pretty sure it was mcmaster-carr not sure if they ship to you, but their shipping is great in the US (i can get something same day if i need it).
p.16 #5 · lens repair, modification and disassembly guide thread
Thanks very much sebboh.
I had a look there when considering buying the brass tube. If they don't deliver directly than I also have a mail forwarding service provided by Australia Post out of Oregon!
p.16 #6 · lens repair, modification and disassembly guide thread
kevko wrote:
Would you be able to post the 3D print file somewhere when ready? I think it's time for me to convert my G45. I actually wouldn't mind going in with others to order a set of rings, but I'm not sure if there is much demand or if they can still be made for small orders.
My intention is to post the finished file here.
There is some difficulty in printing the disk when there is raised areas on both sides, some sort of support is needed, or a different approach.
p.16 #7 · lens repair, modification and disassembly guide thread
LightShow wrote:
My intention is to post the finished file here.
There is some difficulty in printing the disk when there is raised areas on both sides, some sort of support is needed, or a different approach.
hmm, the printer's i've used automatically figure out how to build a support for whatever you're printing. the one we have at work now has a setting for how dense the support scaffolding is.
p.16 #9 · lens repair, modification and disassembly guide thread
LightShow wrote:
But then the supports have to be broken off and cleaned to a smooth finish so everything sits flat.
yeah, that'll probably be required no matter what if you want the lens to sit at the proper orientation. 3D printers aren't super good at making smooth surfaces.
p.16 #10 · lens repair, modification and disassembly guide thread
LightShow wrote:
My intention is to post the finished file here.
There is some difficulty in printing the disk when there is raised areas on both sides, some sort of support is needed, or a different approach.
just remember this as i was working on a similar problem – another solution to this problem is to remove unnecessary parts from the rings.
here is what the back of the g45 rear ring looks like as i drew it to be machined: http://c1.staticflickr.com/1/594/32291272545_0a9f868ddb_b.jpg
that lip around the edge is just there to help center the m-mount if you buy an m-mount that you need to drill mounting holes in. it's unnecessary if you're mount already has the mounting holes in it. removing it will make 3D printing much easier since there is now a flat surface: http://c1.staticflickr.com/1/460/31480845353_95f350056e_b.jpg
the same can be done with the front ring by removing the surround that comes up around the g45 filter threads.
it won't be as pretty cosmetically, but it'll still function as well and be easier to machine or print. if you really want you could print each ring in 2 pieces as well to preserve all aspects of the original design...
in any event, i finally got around to installing autoCAD on my computer, so i can give people STL files of the various rings if there is an interest.
p.16 #11 · lens repair, modification and disassembly guide thread
Thanks Sebboh (Derek?), I would love these 3D files please. I have a friend with a cheap 3D printer and a continued struggle with converting my G45 via alternative G45 mod. approach, so the Rokkor 55 donor lens is looking more and more preferable.
(Interestingly my G45 has some dimensional differences from the one shown in the above link and I'm left with nowhere to go to achieve infinity, except for shaving off some depth in the original mounting base of the Contax lens).
p.16 #12 · lens repair, modification and disassembly guide thread
lenticular11 wrote:
Thanks Sebboh (Derek?), I would love these 3D files please. I have a friend with a cheap 3D printer and a continued struggle with converting my G45 via alternative G45 mod. approach, so the Rokkor 55 donor lens is looking more and more preferable.
(Interestingly my G45 has some dimensional differences from the one shown in the above link and I'm left with nowhere to go to achieve infinity, except for shaving off some depth in the original mounting base of the Contax lens).
it's important to note that these .stl files are measured in inches. if you're printer is set to millimeters you will need to multiply by 25.4 in all dimensions.
printing the g35 rings came out fine, but i don't really trust the plastic for achieving perfect alignment and maintaining it over time and temperature change...
p.16 #13 · lens repair, modification and disassembly guide thread
Thanks a lot for these.
An important clarification: are these for the G35? My immediate requirement is for the G45 however I presume that most of the dimensions are for mating with the Rokkor body. I can always drill new mounting holes should the G45 differ.
I note the need to convert to mm!
Jan 20, 2017 at 05:11 AM
AmbientMike Offline • • • • • • [X]
p.16 #14 · lens repair, modification and disassembly guide thread
It was very easy to stop down a Nikkor 20/2.8 AF with stuck aperture pre-D for mirrorless use. I could probably get it to work on a Nikon if I had to.
I just unscrewed the 3 screws on the bright, metal lens mount. Pulled off the back. Underneath, there was a ring that wasn't attached to anything. I removed that.
There is a lever you can move, which stops the lens down.
If anyone needs photos or assistance, you might pm me, I've been on FM regularly lately.
The D version may be a bit harder, this guy pulled out the 3 screws on the center, matte black, back of the lens, and detached electronic contacts. But I didn't have to do that. This is a more proper way to do it, but a bit much for me right now.
I'm pretty happy using the lens at f/8 on mirrorless. Better than 2.8. If I had a Nikon body, I could probably hold it up to the camera and not attach it, so that it didn't open up to f/2.8 every time, where it sticks. Kind of like using a T-mount lens. But it might take 3 hands.
I'm interested in suggestions on how to fix my lens, if anyone knows a better way.
p.16 #15 · lens repair, modification and disassembly guide thread
lenticular11 wrote:
Thanks a lot for these.
An important clarification: are these for the G35? My immediate requirement is for the G45 however I presume that most of the dimensions are for mating with the Rokkor body. I can always drill new mounting holes should the G45 differ.
I note the need to convert to mm!
those that i posted are for the g45, the g35 ones are very different, more complicated, and would not allow focus closer than infinity if you tried to mate them to a g45.
p.16 #17 · lens repair, modification and disassembly guide thread
if anybody is interested in g35 rings here's what they look like: http://c1.staticflickr.com/1/760/31631141523_ba6fddd84d_o.jpg
in order to get infinity you have to connect the m-mount directly to the rokkor helicoid and the left most ring in the image above is used to hold the aperture ring in place. the front ring is made of 2 pieces to make 3D printing easier. for machining out of aluminum i would probably combine the two pieces on the right into one.
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