The CZJ Sonnar to LTM Conversion

[Brian]

What can I say? There is not much to this, and I'm surprised a shop did not do this a long time ago.

Parts Required: J-3, LTM version. Contax mount Carl Zeiss Jena 5cm F1.5 lens, below serial number 3Million. I've done this on lenses from 1935 through 1939, 8 in all. I think the post-war lenses changed thread size. That is definitely true of the F2 lenses.

Step 1: There is a set screw in the back of the Contax Mount lens that holds the optics module into the mount. Remove it.

Step 2: With the set screw out, unscrew the optics module. A rubber mouse pad, or rubber sheet may be required.

Note: I've run into 2 leness that had an extra set screw to hold the rear optics module in place in the optics module. They were both "T" coated lenses. One of them was misassembled and the set screw head was embedded in the Contax Mount itself. Dremel. I'm getting good at cutting up lenses with dremels. Broke three cutting disks on a Canon 50/1.2.

Step 3: Unscrew the J-3 optics module from its LTM mount. Best to use a lens made before 1963. The thread size of the variable stand-off ring changed on some of them. There is no set screw holding it in. The LTM mount itself did not change. If you use a later J-3, at worst you will have to polish down the variable stand-off ring of the Zeiss lens. Getting the earlier J-3 saves some elbow grease. Lots of Elbow Grease.

Zeiss module on Left, LTM mount behind it. J-3 on the right.

[Brian]

4) I've found it necessary to trade the variable stand-off rings between the J-3 and Zeiss. Unscrew the two set screws, trade the rings. The J-3 ring is about 0.5mm thinner. Most of the lenses I've done, the Zeiss ring was too thick and the module could not be collimated.

5) Time to collimate in the LTM mount. You should have enough shims between the two lenses.

6) You will need to reposition the aperture ring if you want the F-Stops to line up. This is not necessary on all lenses. I've had 3 of the 6 be perfect fits- the LTM lens and Contax lens threads started on a standardized position. On those, the lens collimated in the new mount and the F-stop lined up perfectly. The others- undo the set screws, and reposition the ring. You will probably need to tap out new screw holes. I use a hand drill with a triple-zero drill bit.

My special device- found for $15 on Ebay, a through the lens viewer with ground-glass and a high-power magnifier. I put the lens on a known good Canon IIf, focus to a test target, set the TTL viewer up, set the focus to what the IIf indicated, and shim the optics module until the actual focus agrees.

You'll have to mount a focus screen or film strip on the back of your camera, check distance at the filmgate- unless you can find one of these.

Kim Coxon's excellant site has instructions for lubing the LTM J-3 mount. Figure the LTM lube-job into it, and the setting of the optics, etc- you can spend a couple of hours doing this. The last one took 4 hours, but I took my time, cleaned the inner elements and flood cleaned the blades.

[Brian]

And Done.

http://www.ziforums.com/attachment.php?attachmentid=39&stc=1&d=1229474695

[notraces]

This is awesome, Brian -- thanks for sharing!

[Brian]

Thankyou, Bob.

I just completed #7. I took more detailed pictures during the process, and noted some fine points that can be "gotchas". As I get some time, I'll post those photo's and notes here.

I've put some galleries up with photo's from my converted lenses.

http://www.ziforums.com/album.php?albumid=16

Also- I've now collected two Wartime Zeiss lenses. The 1941 lens is in near mint condition, and the mount is working well after some repair. I'll be able to do a side-by-side comparison. I also picked up a later wartime lens, needs a rebuild. You can tell there was a shortage of top quality material for the mount. I will be dismantling it "probably" next week.

[jmkelly]

Brian - thanks for the de******ion. Maybe you won't end up with folks asking you to do these simple hybrids for the rest of your life after all :redface:! The TTL magnifier looks like the secret sauce - a big help anyway. The rest is pretty straigtforward. Time for me to go tool shopping.

[jmkelly]

OK Amin - time to man up here - why is "s c r i p t" blocked even in the middle of a word? I'm cross posting this in "what can be done to make this site better?"

[raid]

noitpircsid backwards ... will this be removed? Just a test.

d e s c r i p t i o n de******ion ****** last word was s c r i p t

[Romeo]

What do you do with the Zeiss Jena barrels after the conversion?

Use them as earrings? (J/k)

[Brian]

I use them to convert the J-3 optics modules to Contax Mount.

http://www.ziforums.com/album.php?albumid=89

Focus on the one blade of grass in front of the stalks, wide-open.

http://www.ziforums.com/picture.php?albumid=89&pictureid=715

I have one on the Contax II made from a 1955 KMZ, formerly in LTM. I have another that is collimated for Nikon S-Mount.

But I do have more Contax Mounts than I have converted. Some I hold back in case I decide to switch one of my modules back to Contax Mount. I also like to experiment, and convert lenses to Contax and S-Mount. I still plan on making a Leitz 5cm F3.5 "Varob" enlarger lens (really an Elmar) into S-Mount for the Nikon RF. The left-over parts are perfect for this.

[Trius]

I still plan on making a Leitz 5cm F3.5 "Varob" enlarger lens (really an Elmar) into S-Mount for the Nikon RF. The left-over parts are perfect for this.

For flat field work? Or for general use to see how it works? Might be interesting bokeh???

[Brian]

The Varob is an Elmar optics module in a fixed mount for an enlarger. So- I just want an Elmar for S-Mount, and this lens was cheap- $35. Can't get an Elmar for that amount.

[Romeo]

But I do have more Contax Mounts than I have converted. Some I hold back in case I decide to switch one of my modules back to Contax Mount. I also like to experiment, and convert lenses to Contax and S-Mount. I still plan on making a Leitz 5cm F3.5 "Varob" enlarger lens (really an Elmar) into S-Mount for the Nikon RF. The left-over parts are perfect for this.

That's quite an effort to go through!

The Sonnar 5cm lenses are really sweet on a Contax. Not sure about on a Leica... How do you find the larger f1.5 types on the small IIIc/d/f type camera?

Would there be any reason why a Contax rangefinder --> LTM 39mm adapter wouldn't work, preserving the Contax lens for both Leica and Contax rangefinders?

[Brian]

I have three adapters: Contax-> M-mount; Nikon -> M-Mount, and Contax to LTM mount. They work... But- they are not as smooth focussing as the converted lenses. One had a slight wobble in it, filling the helical with vaccum pump grease "helped" but not perfect. One was perfect for S-Mount lenses. The LTM adapter required that the Zeiss Opton Sonnar be shimmed to correct some focus error in the adapter.

The LTM Sonnar's are small, close to a Canon 50/1.5. I've used them on Several Leica's, including the IIIa, CL, and M2.

I'll have to post a thread on converting the 5cm F2 Sonnar's using a J-8, and using the left-over Contax mout to make a Collapsible I61L/D for the Contax. Very sharp.

[Trius]

Interesting ... sounds like the Varob wasn't an Elmar tweaked for flat field/enlarging. Good info.

[Brian]

What do you do with the Zeiss Jena barrels after the conversion?

Use them as earrings? (J/k)


Yesterday, I made two of the better left-over J-3 modules into Contax mount lenses. One is shimmed for the COntax, the second is shimmed for the Nikon S-Mount. You have to shave the first few millimeters of the Contax shell off, as the J-3 module mounts much deeper into it. Otherwise, you cannot see the F-Stops.

http://ziforums.com/album.php?albumid=152

http://ziforums.com/picture.php?albumid=152&pictureid=1397

This should give an idea of the amount of shaving required.

http://ziforums.com/picture.php?albumid=152&pictureid=1400

I shot a test roll today, and will be putting these lenses in the For Sale after I confirm their operation. I'm thinking $60+shipping. They will be up in a few days.

The 1958 lens is a "Hacked-Hacked lens". The front element is from a 1974 J-3, the original was really bad. The lens came out with a softer focus and Bokeh than most J-3's. For that reason, I shimmed it for S-Mount. Hard to find a soft portrait lens for a Nikon RF!

1958/74 Hack. At F1.5.

http://ziforums.com/picture.php?albumid=97&pictureid=1266

http://ziforums.com/picture.php?albumid=97&pictureid=1267

I'd keep it, but I have Many, Many Sonnar lenses.... Eight J-3's alone. I do not want to be too greedy.

[honpan]

After reading this post, I am tempted to buy a Sonnar 50/1,5. I read about fake Sonnar 50/1,5 in LTM. Ever heard of any in Contax mount?

Since you are talking about CZJ sonnar, I assume later Opton sonnar can't be modified. Am I right?

Sorry for diggging up this post, and thank you. ;)

[Brian]

I have not found a suitable focus mount for the Opton lens.

I have never seen a fake Sonnar in contax mount. A number of "fake" Sonnars that I've taken apart are made of real components, probably assembled after the war.

I just did another conversion this wekend- a 1939 CZJ Sonnar "T". Very crisp.

[honpan]

Thank you very much for your clarification. I shall keep an eye on the an affordable CZJ sonnar!

[sfox]

Hi Brian,
This is impressive ! I have a few CZJ on hand so I am going to give it a try.
I have a few questions here:
1. What is the name (and Brand) of your TTL collimator? It 's good to have one. I htink it would be better than KY's camera/ground glass method.
2. I saw that you have lots of shimming rings. Where did you get those? What kind of material is suitable if I need to make one (and of course, easy to make)?
3. Honpan menitoned Opton here. Does it mean newer type of Sonnar in general cannot be connverted? I have CZJ coated types similar in design (I think) as Opton types.
Thank you!

[Brian]

1) The TTL viewer was off of Ebay, and I think it was made by Canon. Probably made in the 1950s, and the best $15 item ever won off of Ebay.

2) I have collected shims from a number of parts lenses, most of them Jupiter-3's. I have made shims out of aluminum tubes. The easiest material to work with is Aluminum Foil, ~0.05mm per layer. I have also "polished down" thicker shims and old retaining rings as required.

3) The Post war CZJ Sonnars and West German Sonnars are a different optical fixture than the Pre-War and Wartime CZJ Sonnars. After Sn 3million or so, the design of the CZJ lenses changed. If the aperture ring has "wings" on it, it should fit right into a J-3 focus mount.

[sfox]

Thanks. Will give it a try ...

[sfox]

Hi Brian,
One more question - Can a 50/2 Collapsible CZJ Sonnar be converted to LTM? I guess not ? Thanks

[john neal]

Hi Brian,
One more question - Can a 50/2 Collapsible CZJ Sonnar be converted to LTM? I guess not ? Thanks

Hmm, didn't Brian already do that with a J8 mount?

[Brian]

Yes- sorry I missed the question.

I have converted 8 CZJ Sonnars to LTM using a J-8 mount.

[mikhail33]

Hi brain,
Do you have any j-3s or czj converted to ltm lenses for sale? Got my rangefinder not too long ago and i've been drying to get a sonnar lens in the lower price range(being a student and all that :P)!

[Brian]

No- I am afraid not. Prices on J-3's and Sonnars have risen in the lkast year. The days of the $50 J-3 and $100 Zeiss Sonnar seem to be over, at least for now.

[Zarkon]

Can I use a J-8 LTM as the source for converting my CZ Opton 50s? This thread seems to focus on the J-3 but the J-8s are cheaper and I want to convert my CZ 50 f2 first (which should be a better fit to begin with - or not)...

Thanks - btw this forum seems more active than the contax section of RFF - good work guys (and gals).

[Brian]

The CZ Opton optics module will not fit in a J-8 focus mount. A Collapsible Carl Zeiss Jena 5cm f2 Sonnar will fit: a set screw holds the optics in the mount, module unscrews from the collapsible, and into the LTM J-8.

http://www.ziforums.com/picture.php?albumid=118&pictureid=2099

This is one of my 5cm f2 conversions.

[Zarkon]

Thanks Brian. What can be done to use my CZ Opton 50 1.5 on my Bessa?
Is adapting a Contax rf mount to the M the only way to use these lenses?

I've purchased a few junked Kievs for that purpose. How much distance (in mm) is there between the M mount flange surface and the inside of the Contax/Kiev base plate? Any hints or instructions on this project...

[Brian]

Th easiest way to use the Zeiss Opton lenses on an M-Mount camera is to get an "Amedeo" adapter. Right now- that is what I use for my Zeiss opton on a Leica.

http://www.amedeo.muscelli.net/

I'm still looking for an easy way to do a conversion. So far- custom machining would be required. The Amedeo adapters are well made, easy to use, and RF coupled.