IVSB2 focus query

[calvinhobbes]

my first post on this board, steep learning curve discovering rangefinders. Ebay doing well from me...
my question, I bought a ivSB2, gorgeous machine, then 2 canon lenses, pictures are sharp. so then bought a Jupiter 8 and an industar 61LD. both are clean, the 61 is almost new. when I focus with the canon lenses, the rangefinder patch at infinity lines up perfectly, is focus looks correct. however, both Russians at infinity the patch won't align , close but not complete. I haven't put a roll though to test if this translates to out of focus images (I assume it will), I believed these lenses were compatible withe the body, have I made a rookie error and should move them on?
thanks, Ian

 

[Duofold RF]

Canon and Russian LTM have different thread pitch 39mm x 24tpi vs 39mm x 1mm leading to potential focus inaccuracies

M39 lens mount - Wikipedia

en.wikipedia.org

 

[calvinhobbes]

thanks, Ive been reading that LTM is actually a Whitworth thread vs the Russian 1mm, so will the rangefinder inability to focus at infinity result in poor images or will stopping down make it acceptable....or just buy correctly?!

 

[calvinhobbes]

Ive answered my own question, google search led me back here! asking about using soviet m39 lenses on leica screw mount cameras

 

[peterm1]

thanks, Ive been reading that LTM is actually a Whitworth thread vs the Russian 1mm, so will the rangefinder inability to focus at infinity result in poor images or will stopping down make it acceptable....or just buy correctly?!

If the error only manifests at infinity stopping down will often tend to reduce the error in practice. But I have not used Russian lenses on Canon RF equipment when I owned them (and I owned several) so I cannot be definitive about the extent to which stopping down will improve the results. Of course at closer ranges where DOF is inherently less at all f stops, there is a risk that the problem might reassert itself depending in part upon whether the lens is back focusing or front focusing. If the lens is back focusing, typically there is less latitude for error as the available depth of field in front of that point is less (mostly I believe that about 2/3 of a zone of focus falls behind the point of focus and only 1/3 falls in front. Thus, if back focusing there is less latitude to fix things by stopping down though at small enough f stops this is still likely still to provide a workable fix.)

You might also try focusing using hyperfocal focusing rather than relying on the rangefinder when shooting at infinity. Hyperfocal focusing is designed to maximize the extent of the zone of focus by taking full advantage of the more extended zone available when using it.

Hyperfocal distance - Wikipedia

en.wikipedia.org

My preference would be to suggest you buy something like a Canon (or Canon "Serenar" lens - essentially the same) 50mm f1.8 as a starting point as they are eminently affordable, common and very good lenses. They are great lenses in fact and should work a treat with your IVSB2. If buying from Japan just be careful as its long, hot, wet summers can play merry hell with lenses - often leading to fungus and or fogging. But Japanese sellers tend to be careful and pretty honest but just make sure you check carefully to know what you are getting in terms of optics and be aware that some sellers when they say a lens is in excellent (or similar) condition they are only referring to the cosmetic and mechanical condition, not necessarily the optical condition which they tend to deal with separately. BTW the IVSB2 is a great camera and is one that I used to own before I went fully digital.

 

[boojum]

Yes, the old Canon 50mm 1.8 is a wonderful lens and the red-headed stepchild in that it is more ignored than noticed.

In Jupiter 8's QC is the problem. KMZ is/was the finest builder of J8's. And they may need to be tuned to M bodies and the like for the correct distance for lens to capturing surface. That said I have a '57 J8 that is just about the best 50 I have. It's really good for color and IQ.

Night scene in the Astoria Harbor, West Mooring Basin by Bornstein's Sea Food. M9 - '57 KMZ J8 by West Phalia, on Flickr