backfocus remedy ?

[gliderbee]

I have a J9, J8 and J3 and I tested them all on my R-D1s (wide open, closest distance); as I understand it, they all backfocus (see pictures hereunder).

Should I add shims or just the contrary, remove shims or put thinner shims in it, to have them focus correctly on the R-D1s ?

But more important to me:
I suppose (not tested yet), these lenses are probably correct for FSU camera's (I have a Zorki 4, FED2, FED4 and FED5).

IF I correct them for the R-D1s, will they also be ok for a Bessa R3A, a Leica 6 and the like (meaning: more modern camera's) ? And if corrected, I guess they will NOT be ok anymore for the FSU's, right ? So it comes down to choices ?

And since I have plenty of 50mm lenses for modern camera's and also a VC 75mm and a Konica M-Hexanon 90mm, I might best just test them on the FSU's and if ok, not touch them, since on my FSU's, I can't use the 90mm (I could use the VC75, since it's LTM) ?

Here are the pictures:

J3:

J8:

J9:

 

[ferider]

With normal shimming, you can only correct for close focus, but then your lenses will be off at infinity and on your Russian cameras (assuming they work on those). Which could be OK if you are willing to always stop down at infinity.

Since you have lenses that work to Leica standard on your RD, I would not touch the Jupiters and use them with the Russian cameras they work on (assuming they do). BTW, the 75 is a great lens.

Roland.

 

[Sonnar Brian]

You pretty much have it: if you correct them to the Leica standard, they will front-focus on the Russian cameras. When I shim a J-8 or J-3, I set it for close-up and wide-open. Focus holds out to 10m or so, after which the lens needs to be stopped down to F2.8 or F4. The SOnnar focus shift pushes the focus toward infinity.

On the older J-3 and J-8, if the lens is way off you can try to move the rear element in closer to the front, which reduces the focal length very slightly.

 

[gliderbee]

Focus holds out to 10m or so, after which the lens needs to be stopped down to F2.8 or F4. The SOnnar focus shift pushes the focus toward infinity.

Thanks Ferider and Brian. There's only one thing I don't quite understand then: if, after shimming, focus is ok, doesn't the increased depth of field at infinity compensates for the backfocus, even wide open ? Or is it still that small ?

 

[Sonnar Brian]

The Russian lenses are built to the Zeiss focal length of ~52.4mm. The Leica standard is a nominal 51.6mm. The focus throw of the Russian lens when moved from 3ft to infinity is 0.1mm longer than the Leica lens. SO: you can shim it for close-up and wide-open, but the lens will not quite reach infinity. The Sonnar focus shift helps, and DOF at F2.8 covers the residual error.

to complicate matters, the focal lengths are nominal: some J-3's and J-8's have a focal length shorter or longer than the nominal 52.4mm. I saw a 1953 J-3 on Ebay with the original test sheet indicating 52.6mm.

Easiest fix: at distance, focus slightly past what the RF indicates. Use F4 for infinity.

 

[Chriscrawfordphoto]

Gilderbee, where did you find that focus target printout. Is there a site to download it from?

 

[Clovis]

Found at:

http://focustestchart.com/chart.html

Link at the bottom of the page.

 

[Chriscrawfordphoto]

Thanks Clovis!

 

[ampguy]

Here is infinity on a Sweeny shimmed J3 (alum chrome) as reported by seller at infinity with M8, stopped down to either f4 or 5.6:

 

[gliderbee]

The Russian lenses are built to the Zeiss focal length of ~52.4mm. The Leica standard is a nominal 51.6mm. The focus throw of the Russian lens when moved from 3ft to infinity is 0.1mm longer than the Leica lens. SO: you can shim it for close-up and wide-open, but the lens will not quite reach infinity. The Sonnar focus shift helps, and DOF at F2.8 covers the residual error.

to complicate matters, the focal lengths are nominal: some J-3's and J-8's have a focal length shorter or longer than the nominal 52.4mm. I saw a 1953 J-3 on Ebay with the original test sheet indicating 52.6mm.

Easiest fix: at distance, focus slightly past what the RF indicates. Use F4 for infinity.

Ok, one final question (for now, I think :angel🙂: what about the Canon rangefinders (IVSB, Canon P) ? Are these like Leica, like FSU or yet something else... like Canon ?

 

[Mablo]

Canons are like Leica.

 

[john_s]

This might be interesting:

http://www.dantestella.com/technical/compat.html

 

[Sonnar Brian]

All you have to do is read the spec sheet that comes with an FSU lens. The focal length is clearly shown as the Contax standard. My J-3 spec sheets show 51.4mm, and I saw an LTM J-3 with a spec sheet showing 52.6mm. That is the Contax standard, not the Leica standard. The Canon, Leotax, Nicca, and other Japanese Leica based cameras are all standardized to 51.5mm. The Russian cameras are based on the Contax standard.