Focusing compatability with FSU lenses

[pfogle]

Hi, I've been reading quite a few threads about the R-D1 rangefinder accuracy, with people reporting typically 4-5 cm front focusing at 1m with Jupiter lenses.

I'm including a link (here) to a rather long and technical page which covers this issue. It seems that the Leica R/F cam is designed around a lens with a nominal focal length of 51.6mm (usually labelled 50mm), whereas the Russian lenses were designed to the same spec as the pre-war Contax which used a length of 52.3mm - which explains why you can't get accurate focus at both infinity and 1m.

I strongly recommend that you do NOT calibrate your rangefinder using a Russian lens - you'll give yourself indigestion, and screw up the adjustment for Leica/CV lenses as well!

 

[Jocko]

This is a very controversial topic in the FSU forum, with ramifications beyond the RD-1. In the past I have argued strongly against Dante Stella's theory. I thought that variations in quality control explained apparent incompatibility, but a recent job-lot of Jupiter 8s has led me to question that view.

I regretfully think that there may well be what we might call a "consistent error" in the lens, roughly of the order described by Phil, perhaps a little greater. This would seem to suggest that Stella is right, although it does need proper testing.

Cheers, Ian

 

[tmessenger]

Well if the specifications for the Leica lens design I found on the net are correct (1M ~ infinite = 3mm of cam lift) then there is a problem. I've measured 3 Russian lenses, Jupiter-12, Jupiter-8 and Industar 22 and all these lenses have around 3.1mm of cam lift from 1M to infinite. I'm thinking the fix is to machine the cam that would take care of it. It's only .1mm (.004") and there is some DOF tolerance to work with so it doesn't have to be exact.

Regards,

Tim

 

[Xmas]

Ian

If you wait until Tim machines and hand files the last few thou, then these lenses will disprove Dante Stella's theory?

I must not tease Ian, I must not tease Ian, ... sorry

Noel

 

[pfogle]

Well if the specifications for the Leica lens design I found on the net are correct (1M ~ infinite = 3mm of cam lift) then there is a problem. I've measured 3 Russian lenses, Jupiter-12, Jupiter-8 and Industar 22 and all these lenses have around 3.1mm of cam lift from 1M to infinite. I'm thinking the fix is to machine the cam that would take care of it. It's only .1mm (.004") and there is some DOF tolerance to work with so it doesn't have to be exact.

I don't think that will work, as there will still be 3.1mm of movement, just starting from a different baseline.

The problem is that the screw pitch is different for the different lens specs.

I may be wrong...

 

[Xmas]

Some lenses have a rotating rear ring and machining would be effective e.g. the Elmar clones - but difficult, some of the leitz lenses have been hand finished by an artist with a file.

Linear lenses wont work you are correct.

Noel

 

[tmessenger]

I don't think that will work, as there will still be 3.1mm of movement, just starting from a different baseline.

The problem is that the screw pitch is different for the different lens specs.

I may be wrong...

The ramp needs to be tapered (non-linear).

And yes I believe the screw pitch is different then the Leica / CV lenses.

Tim.

 

[tmessenger]

More fiddling

More fiddling

If you've read my other post on RF adjustment 101 you know I've been trying to get my finder aligned with a J8 lens at infinity and 1m. Well after doing some tests on the lens today I've discovered the collimation on the lens was off. I've reset the lens collimation using very thin .001" (.025mm) shims I've now got the lens right on the money at infinite. I have my baseline (1m.) rangefinder eccentric screw set all the way over and I now have an accurate finder at infinite and 1m. (well actually it's back focusing by about 10mm. at 1m. but I can live with that).

I can't believe how well the J8 performs, it's very nearly as sharp at f2. as it is stopped down just lacks some contrast. I'm kind of shocked this $30 lens beats up on some the best lenses I've tested on my dslr. Next up is my J12 this lens already looks very good but I'm checking the collimation to make sure.

Regards,

Tim

 

[pfogle]

]I can't believe how well the J8 performs, it's very nearly as sharp at f2. as it is stopped down just lacks some contrast. I'm kind of shocked this $30 lens beats up on some the best lenses I've tested on my dslr. Next up is my J12 this lens already looks very good but I'm checking the collimation to make sure.

Tim, I've got a Jupiter-8 that I rarely use... your comment has reminded me to get it out again!

I also did some comparisons last week between the J-12 and a Canon 35/2.8 I happen to have. I found the J-12 rather flarey in backlight, and the colours a bit weak compared to the Canon. On the other hand, the J-12 is bitingly sharp in the center - better than the Canon even at f8.

A question - the J-12 is definitely out of alignment and needs collimating. One side is really fuzzy even stopped down. Do you do collimation yourself? Is it hard? I'm reluctant to spend money on the thing!

cheers
Phil

 

[tmessenger]

A question - the J-12 is definitely out of alignment and needs collimating. One side is really fuzzy even stopped down. Do you do collimation yourself? Is it hard? I'm reluctant to spend money on the thing!

cheers
Phil

If your lens is only fuzzy on one side then I don't believe collimating will not take care of it. It's most likely that one of the elements is off center.

Yes I do my own collimating and you can really nail it with the Epson because you can make changes and then check the changes at 100~200% in Photoshop. I start by making a reference mark between the lens module and focus module (so you know where you're at with the current set up). I then back out the lens module (count the number of turns until the lens module separates) then remove a shim and screw the lens module back in the same number of turns and line up the marks. The lens module is now in the same place but loose. Mount the lens, set it to infinite / wide open and take a shot of a distance target. Now turn the lens in or out a 1/4 turn take a shot (use the marks you made on the two modules to keep track of new positions). Do another 1/4 turn in or out take a shot..etc. Now review the shots and see how the original compares to the new positions. After you've determined the optimal position it's time to add or subtract shims. I use hard-cast duct tape (it's aluminum tape about .001 thick) to fine tune the position, you can get it from suppliers that sell duct parts to heating and air conditioning installers. I stick a thicker shim to it then cover it with a small piece of wax paper and cut around with a x-acto knife to remove the excess material. All of this is a lot faster to do then it sounds and you'll get a feel for it after you do your first lens. Fine tuning to the exact collimited position is the key to the best performance, even just a little off is very noticable wide open. I just finished up my J12, it took me about 2 hrs. and it was well worth it. The before and after is just amazing and both the J8 and J12 now focus properly and I can shoot them wide open with great results.

Regards,

 

[mwooten]

I received one of my J-8's back from Yuri at Fedka yesterday. It is one of the older white metal lens. I have one of the newer black versions that I plan to send off to them (or try the process that Tim discribes above) because its focus is as sharp as fog. Yuri/Fedka cleaned, lubed, and collimated it. I told them that I would be using the lens on an RD-1. I've not had a chance to shoot a great deal with the lens, but from what I've seen the focus seems to be right on.

On the other hand, the Industar-61LD that I bought at the same time as the white J-8 seems to work really well straight from the box, and I really like the results.

Take care,
Michael

 

[Adam-T]

I`ve found the differences the same here - Silver 1963 J8 sharp wide open at F2 and handles far better because the aperture ring doesn`t rotate - Black 1973 version, dreamy below F2.8 though excellent at F4.. Seems like KMZ cheapened out with the later J8s .. Neither will focus to infinity ahh well.

 

[pfogle]

Tim - is there a cure for off center elements? Or is this one for ebay?

 

[Kim Coxon]

Hi, It really depends on what caused the problem. If it has been re-lubed and put back togeyher incorrectly, it could easily be fixed. If the lens has been damaged at some stage, possibly not.

Kim

Tim - is there a cure for off center elements? Or is this one for ebay?

 

[Kim Coxon]

This sounds very much like a shimming problem or that someone has re lubed the lens and reassembled it using the wrong thread on the helix. It is relatively easy to fix. The instructions on my website should help.

http://pentax-manuals.com/repairs.htm

Kim

I`ve found the differences the same here - Silver 1963 J8 sharp wide open at F2 and handles far better because the aperture ring doesn`t rotate - Black 1973 version, dreamy below F2.8 though excellent at F4.. Seems like KMZ cheapened out with the later J8s .. Neither will focus to infinity ahh well.

 

[Ed Schwartzreic]

While my results are not scientifically based, I have a SM J12 which is a wonderful performer, even wide open. It focusses accurately on the R-D1. On the other hand, I tried a different J12 which was totally "out" and front-focussed throughout its range. I tend to see the problem as a QC issue.

 

[tmessenger]

The J8 I collimated would only focus to my infinite target (180m) @ f11 before collimating that's how far out it was (need the extra DOF). Now it's right on @ f2.

Tim

This sounds very much like a shimming problem or that someone has re lubed the lens and reassembled it using the wrong thread on the helix. It is relatively easy to fix. The instructions on my website should help.

http://pentax-manuals.com/repairs.htm

Kim

 

[pfogle]

The J8 I collimated would only focus to my infinite target (180m) @ f11 before collimating that's how far out it was (need the extra DOF). Now it's right on @ f2.

Tim

Tim, if I understand you, what you are correcting is the infinity focus, right? So you're not changing the internal relationship of the elements, just the distance of the lens module from the rear focus flange?

I don't really know if my J-8 is accurate at inf, as I tend to shoot closer with that lens, especially at the larger apertures. It's good at 1m out to about 5m, which I got by putting a thin spacer on the back of the focus flange (I just glued a circle of paper onto it), so I expect the inf focus will be out. But since the lens can only be correct (theoretically) at one distance if the pitch of the thread is different from what the cam expects, I'd rather have it as it is, I guess.

The J-12 is another matter - I'll be sorry to ditch it, as it's so sharp over most of the field, but I guess I just prefer the look of the images from the Canon, so that'll be the keeper for when I need a small lens. I've got a CV 35/1.7 as well, which seems pretty good, tho' I have to admit to some gear envy of those of you who have the 'lux asph 😱

 

[tmessenger]

"Tim, if I understand you, what you are correcting is the infinity focus, right? So you're not changing the internal relationship of the elements, just the distance of the lens module from the rear focus flange?"

I did check the lens module but you can only move the rear element out unless you want to remove material, the module was OK as far as I could tell. The problem with both the J8 and J12 was the shimming between the focus module and lens module. Once I got them shimmed correctly at infinite they focused correctly at 1m. I've adjusted my finder baseline for the J8 so don't know how a Leica or CV will do now.

I'm planning on doing a Russian lens shot out (I now have a J8, J12, I61 and I22) I'll let you know how it goes and also compare the best one to my dslr Nikon 45mm P and Pentax 50mm FA f1.4.

I need to measure the Leica cam travel from 1m to infinite to know for sure but based on what I could find on the net it indicates 3mm, the Russian lenses have just a bit more travel. This may not be significant enough to cause problems with a finder adjusted with a Leica lens if the Russian lens is correctly collimated?

If you want to get rid of your J12 send me a PM I'd like to have it for parts.

Tim