I'll work on the pic format in a bit, thanks for the tip.
Just roughing things out to see how it all fits, using the original aperture ring looks like too much trouble after all. As you mentioned for the 28G Sebboh, the 45 will also need a custom "washer" just to be able to screw everything together. In general though, the Rokkor is a good fit and will make things relatively easy, reversible too. I'll get more pics up when I actually get something done

This was just pointed out to me over on RFF Click

Really cleanly done 90G. Going to look a little closer at the original mount again, probably don't have the tools to make it work though. Looking forward to seeing what it sells for...

After looking closely, i.e. completely dismantling the 45G, appears for my purposes I'll be better off using the original 45G lens body than the Rokkor (that said, if anyone wants a near mint Rokkor 55/1.7, contact me). A new slot needs to be milled in the steel body to accommodate a focus tab. A slot and threaded stop is already there but winds up being located on top of the lens in it's otherwise best mounted position. Original helicoid has a very nice feel and one finger resistance. It'll be a much more difficult conversion and not reversible but ultimately much more compact and easier RF coupling. Pics coming... eventually. The conversion using the Rokkor looks much more straightforward and easily reversible, just more difficult to attach some kind of rotating RF coupling. That may be a non-issue though for many folks (myself included, just something I'd like to add on eventually). C'mon, somebody else start dismantling, we need more eyes on this

I did dismantle it (I put the G45 into a Zuiko50M body).
I really wonder how you would make the G45-body focusing...
which part of it should be the rotating part?

Thatspeck wrote:
This was just pointed out to me over on RFF Click


Thats comparable to what these people do: http://www.japanexposures.com/lens/
The 90 looks almost like the original. Less so the other Contax G lenses.
The advantage of these conversions is obvious - they can be used with a rangefinder camera.
The disadvantage is that the entire barrel together with the aperture is rotating when focused (at least the 45, 35 and 28mm lenses) - for me this would be disturbing.

m-a-x wrote:
Thats comparable to what these people do: http://www.japanexposures.com/lens/
The 90 looks almost like the original. Less so the other Contax G lenses.
The advantage of these conversions is obvious - they can be used with a rangefinder camera.
The disadvantage is that the entire barrel together with the aperture is rotating when focused (at least the 45, 35 and 28mm lenses) - for me this would be disturbing.

yeah, i don't have any interest in using the lenses on a rangefinder, so i'd rather the optics and aperture not rotate. also, i don't really like the way the shorter lenses look after that conversion.

Thatspeck: how much are you looking to sell the rokkor 55/1.7 for?

m-a-x, the Miyazaki san conversion where the front end rotates doesn't appeal to me either. I'm pretty sure the only thing rotating on that Ebay 90G though is the focus ring he added on at the mount end. With both of these the focus ring (or tab) is right up against the camera body. If what I'm thinking will work, the focus tab will be about half way out the lens and be at the bottom when mounted. Here is a pic of the stock slot in the body with threaded stop (approx 1/3 of the way forward from the mount)



You could attach a longer post to that one but it winds up on top of the lens when mounted (assuming you want the aperture indicator centered on top). I hope to mill an identical slot on the other side but about 7mm further forward. Then add a threaded post (or two) and focus tab. An identical slot will need to be milled into the cosmetic aluminum outer shell. This should still leave plenty of strength left in the body, it's steel. Sadly, these lenses aren't quite up to the build quality of the old Rokkors but still a bit better than modern stuff. The helicoid appears to be aluminum on aluminum, has a nice smooth feel though with one finger resistance.

Am I missing anything glaringly obvious that will make this impossible

Sad to see how little that converted 90G sold for, Click
Sebboh, pm'ed you

Thatspeck wrote:
These will do the trick for removal of the vanity ring;
Click
$2.99 at the hardware store. Cut the ends at various spots to get different sizes. Now for the real work...

Ah, perfect. I'll start there. Failing that, I'll click on over to micro-tools for the real thing. I've got a Tokina 28-70 with Macro that is getting that subtle mildew inside and it seems silly to toss it out without attempting a DIY cleaning. All I need is to just get it started....

Thanks for the tips, gang. Cool stuff!

Thatspeck wrote:
You could attach a longer post to that one but it winds up on top of the lens when mounted (assuming you want the aperture indicator centered on top). I hope to mill an identical slot on the other side but about 7mm further forward. Then add a threaded post (or two) and focus tab. An identical slot will need to be milled into the cosmetic aluminum outer shell. This should still leave plenty of strength left in the body, it's steel. Sadly, these lenses aren't quite up to the build quality of the old Rokkors but still a bit better than modern stuff. The helicoid appears to be aluminum on aluminum, has a nice smooth feel though with one finger resistance.

Am I missing anything glaringly obvious that will make this impossible



i believe that should work from my memory of the g45 internals and your picture. i would recommend making the new slot slightly longer and removing the set screw shown in the picture since the helicoid has a little extra throw that can be added to your mfd. also, i might add an extra aluminum ring, maybe with a rubber grip to the focus post to cover up the slot you mill in order to prevent getting dust and grit inside the lens (you could possibly just replace the middle ring of the lenses exterior shell rather than putting a slot in it).

I use rolls of electrical tape sized to fit the id ring, then pull some tape off and wrap it back on backwards(sticky side out) and hanging partially off the end,
rear lens caps also work with some tape on backwards.

For those that don't have the skills, there is another conversion I found that was tempting in this thread:
http://www.rangefinderforum.com/forums/showthread.php?t=111550
in this post shows a prototype(I believe):
http://www.rangefinderforum.com/forums/showpost.php?p=1772123&postcount=43

Thatspeck wrote:I hope to mill an identical slot on the other side but about 7mm further forward. Then add a threaded post (or two) and focus tab. An identical slot will need to be milled into the cosmetic aluminum outer shell. This should still leave plenty of strength left in the body, it's steel. Sadly, these lenses aren't quite up to the build quality of the old Rokkors but still a bit better than modern stuff. The helicoid appears to be aluminum on aluminum, has a nice smooth feel though with one finger resistance.
Interesting idea. Thanx for pointing this out.
I will dismantle one of the two that I have during the next days to have a look myself.
I want to make a second Oly-Zeiss, anyway.
Thatspeck wrote:
Sad to see how little that converted 90G sold for, Click
Yes, not very much.

LightShow wrote:
The downside is I don't think it's cheap, but it is RF coupled.
PM "digitalintrigue" for details on that forum.
It is very good looking, though.

All good stuff guys, appreciate everyones eyes on this. Sebboh, I don't as yet see why the slot couldn't be made a little longer, as long as there's enough metal left to hold everything together. I've still not been able to completely remove the helicoid though, the lock ring is deeply inset, I'll have to grind some custom spanner tips to get to the slots. That said, m-a-x, 7mm further forward for the slot may end up being closer to 3-4mm. Too hard to tell until it's completely apart. It would also be possible to use the stock slot rotated so it's on the left side while mounted. Aperture markings would also be 90 degrees to the left, better than the bottom though and much simpler as no new slot needed. Your finger would just start to block an average viewfinder near infinity this way.

Lightshow, I loved the look of that conversion as well but seems it may be years away if ever and likely, $500ish?

LightShow wrote:

does anyone know who can/offer to replace the electronically controlled aperture with the mechanically controlled aperture on the Contax 645 lenses?

bhjazz wrote:
Ah, perfect. All I need is to just get it started....
Gah! I tried starting with a roll of electrical tape. I put enough pressure on the ring, but only managed to get the electrical tape goo all over. Hilarious. I almost think the vanity ring has a bit of glue on it after a visual inspection, so who knows. I will not be defeated, however. On to Microtools!

Jim, hope you'll give us a full report on how the Hawks conversion feels in use. I took a look at his bare helicoid offering, sent an inquiry, so far have not heard back. He's not really offering enough measurements to commit to a $250 mystery helicoid and it appears to be a bit different than the pics above
thminduc, never had one apart, if you find someone to work on the project though, ask if they'll do the same to the Contax N lenses as well please
bhjazz, I'm sure the Micro-Tools rubber rings will do the trick, plus you'll be set for every size you run up against. The Ace hardware chair leg rubber tip worked well for me though for $2.99. I would add that it took a significant amount of force, a clear loc-tite like compound was used on the vanity ring and every other screw in the lens
Still no progress for me, I need to make a tool transition from the garage to indoors as it certainly feels like winter here...

Where do you find these conversion kits - or where do you send your lenses? I read the RF-forum thread and the guy is really secretive dispite many people asking.

I do use the G lenses on a NEX with a cheapo adapter which is "ok", but this seem like a very nice and neat-looking conversion!

Thatspeck wrote:
a clear loc-tite like compound was used on the vanity ring and every other screw in the lens
That is exactly what I can see around the edges of the vanity ring. OK, well at least I'm on the right track.

Thanks!

Looks like I will be opening my Rokkor MC 85/1.7, the aperture is sticking, and I see oil that wasn't there a month ago.

I look forward to hearing your thoughts on the conversion Jim.
I can't seem to find the conversion kit, link?