JML 21mm f/3.5 Lens---Mounting Techniques

kds315* · Post by kds315* » Tue Jun 22, 2010 5:23 am

Guys, I have been contacted by several members here and there seems to be an interest in having a bulk order of a) such JML lens adapters and b) such helicoids made. I have done similar for another forum and would be willing to do that again. For that I would need to collect interested parties (no obligation until final order) so as to find out if teh needed amount of adaptors and helicoids could be collected to make it feasable to go that route. Any interest, please let me know, ideally via postmaster@macrolenses.de as I don't want to flood that thread.

PaulFurman · Post by **PaulFurman** » Wed Jun 23, 2010 10:27 pm

What would the helicoid specs be?

kds315* · Post by kds315* » Fri Jun 25, 2010 12:11 am

Read http://nikongear.com/smf/index.php?topic=22583.0

Bob^3 · Post by **Bob^3** » Fri Jun 25, 2010 7:44 am

Ah, thanks for the link, Klaus. I'm also a member of NikonGear but somehow had completely missed that thread!

Bob

lothman · Post by **lothman** » Fri Jun 25, 2010 10:46 am

Just a suggestion, if we would use a T2 adapter (on ebay for less then 10$) then a simple washer with adoption for the JML, M39, RMS... can be mounted insted of the T2-threaded ring. With the small fixation screws of these adapters even the rotational position of the insert can be adjusted.
Even if you switch your bayonet, you only need another 10$-T2-Adapter.

If there is interest I can do some pics of my conversion this weekend and post the here.

Of course the solution of Klaus is superior, but using a T2-Adapter and a very easy to produce disc-like insert should be much cheaper.

Regards
Lothman

kds315* · Post by kds315* » Fri Jun 25, 2010 10:58 am

Be care ful about that: T2-is standardized but only the inner thread M42x0.75 and the flange focal distance. THE INSET YOU MENTION IS NOT STANDARDIZED. I made a solution like you proposed some years ago, just to find that out the hard (i.e. expensive) way, as all of the sudden different inset sizes appeared on the market and the old ones where no-where to be found anymore! A real bummer...

Or in simple terms: different brands of T2 adapters may have different inset sizes!

A safe route would be to make an adapter like mine with M42x0.75 threads (instead of M42x1.0) that would fit your idea (I have made those for RMS lenses). But I don't see great cost savings...

Craig Gerard · Post by **Craig Gerard** » Fri Jul 02, 2010 12:04 am

Here is an image of a JML mounted to an adjustable focusing helicoid. (fully extended in first image below)

David's o-ring idea was applied in this example. (snug as a bug in a rug)

Len Willan sent up some o-rings and a 30-52 mm step ring adapter for me to try out.

The focusing helicoid is an M42 mount. I think this helicoid is one of Klaus's designs? Adjustable Focusing Helicoid 35mm - 90mm. It is nicely finished inside and out, 'tis a beautiful thing.

JML > o-rings and 30-52mm step ring adapter > Nikon BR2A > Nikon F to M42 adapter > focusing helicoid > M42 to Nikon F dust-catcher adapter > D100.

Carig

Craig Gerard · Post by **Craig Gerard** » Fri Jul 02, 2010 2:38 am

Klaus,

Still very interested in the adapter you've designed for the JML to M42. How are the numbers going?

Craig

kds315* · Post by kds315* » Fri Jul 02, 2010 3:03 am

Have about 6 interested parties, need 10 to make it feasible.

Of these helicoids (as shown above) I have a few left with custom Nikon mount.
(The design is not mine, these are from Taiwan, but I have tested a prototype with best of success)

Craig Gerard · Post by **Craig Gerard** » Fri Jul 02, 2010 4:33 am

Klaus,

Could you send me a PM regarding 'feasible'. I could move a few more; but others are hesitant to commit without a ballpark figure for the adapter.

The helicoid I have (as shown above) was purchased from a seller in Denmark; but shipped from the Orient. The build is solid, the movement precise and the internal barrel is nicely finished to eliminate flare.

Craig

Charles Krebs · Post by **Charles Krebs** » Fri Jul 02, 2010 12:02 pm

Of interest might be the helical focusers here:
http://www.sciencecenter.net/hutech/prices/borg.htm

Especially # 7839, 7840, 7841, 7842.

... and there are others listed both larger and smaller.

These caught my eye: 7857, 7860, 7757,and 7758, because of the 57mm thread size. I seem to remember that the Canon version of the Chinese extension tubes I got were also 57mm.
I have no idea if these are the same thread (pitch could be different and I might be "off" on my recollection of the the diameter) but if it is the same, and those cheap tubes could be added and subtracted at will, it might be useful for some set ups.

There are quite a few other interesting and useful adapters on this page.

Another page worth bookmarking, especiually if you've been looking for some short T-mount extensions is:
http://www.bluefireball.com/Astronomy-Adapter-s/47.htm

kds315* · Post by kds315* » Fri Jul 02, 2010 2:28 pm

Charles Krebs wrote:Of interest might be the helical focusers here:
http://www.sciencecenter.net/hutech/prices/borg.htm

Especially # 7839, 7840, 7841, 7842.

... and there are others listed both larger and smaller.

These caught my eye: 7857, 7860, 7757,and 7758, because of the 57mm thread size. I seem to remember that the Canon version of the Chinese extension tubes I got were also 57mm.
I have no idea if these are the same thread (pitch could be different and I might be "off" on my recollection of the the diameter) but if it is the same, and those cheap tubes could be added and subtracted at will, it might be useful for some set ups.

There are quite a few other interesting and useful adapters on this page.

Another page worth bookmarking, especiually if you've been looking for some short T-mount extensions is:
http://www.bluefireball.com/Astronomy-Adapter-s/47.htm

Yes, I know them for years (and have most of them) yet very expensive at $160 and above the simple helicoids.

dickb · Post by **dickb** » Tue Jul 06, 2010 3:01 pm

Charles Krebs wrote: These caught my eye: 7857, 7860, 7757,and 7758, because of the 57mm thread size. I seem to remember that the Canon version of the Chinese extension tubes I got were also 57mm.
I have no idea if these are the same thread (pitch could be different and I might be "off" on my recollection of the the diameter) but if it is the same, and those cheap tubes could be added and subtracted at will, it might be useful for some set ups.

All the chinese EOS extension tubes I know of have a 60mm diameter, and the Pentax ones as well. The Nikon and Minolta SR (commonly referred to as MD) mount versions are 57mm in diameter. The pitch of these extension tubes seems to be 0.75mm.

The Borg helicoid you refer to is also 0.75mm pitch, so it should be a good match with the Nikon and Minolta extension tubes.

lothman · Post by **lothman** » Sun Sep 12, 2010 7:57 am

for inspiration, the insert I made for a T2-Adapter. I put the JML in the chuck of a lathe and removed the outside rim of the groove and then glued it in the insert mado of black anodised aluminum.

regards
Lothman

lothman · Post by **lothman** » Sun Sep 12, 2010 8:07 am

kds315* wrote:Be care ful about that: T2-is standardized but only the inner thread M42x0.75 and the flange focal distance. THE INSET YOU MENTION IS NOT STANDARDIZED. I made a solution like you proposed some years ago, just to find that out the hard (i.e. expensive) way, as all of the sudden different inset sizes appeared on the market and the old ones where no-where to be found anymore! A real bummer...

Probably Klaus is right here but the three different ebay vendors all had the same diameters. So for all who have the opportunity to work on a lathe, a T2-Adapter ist a good opportunity to start with. I also made some RMS-adapters.