Jupiter 8 Focus Tab & Slow Speed Dial

[Baybers]

G'day,
I'm thinking of buying a 1950's Jupiter 8 lens to mount on my screwmount 111. Up to 1960, I think, this lens came with a focus tab. My question is this- can anyone advise whether the tab will clear the slow speed dial when the lens is screwed on?
I have had an Industar-22 lens that just scrapped past the dial when mounting.
Any general observations about this lens are welcome as well.
Many thanks.

 

[pb908]

i had 2 j8 with focus tab, the tab stop somewhere around 7 o'clock.
i have industar collapsible "fed", the tab stop around 8-9 o''clock
tested with leica iiic.
i assume the multi-helical focusing mechanism can be rotated to the next helix during assembly, i did once in the past. hopefully that answer the question

 

[Dez]

In my experience, the focus tabs on FSU lenses will clear the slow speed dial, but just barely. If you are nervous a few minutes with a file will increase the gap.

Re the idea about the focus helical, the Soviet lenses have a lot of variation in where the focus tab ends up due to inconsistencies in the machining of the screw threads. It's quite challenging to machine a screw thread accurately enough to have the lens always align correctly, and the variation increases as the threads wear. Some variation will also be seen in Leitz lenses, which were made to an order of magnitude better precision. Note that when Pentax went to their SMC screwmount lenses, they added a positive stop to ensure that the alignment for the full aperture meter coupling was always correct.

If you change the helical start, you will mess up the focusing. Don't do it.

Cheers,
Dez

 

[Baybers]

Thanks guys,
Yes the question was simply whether the tab will clear the dial when screwing the lens onto the camera. If the tab is no bigger than the one found on the Industar-22 then all should be sweet. Nevertheless, I will have a file standing by just in case.
Interestingly, the J-12 I have does not 'line up' when screwed on the Leica, yet focuses beautifully none the less.
I confess that talk of helix(s) and the like make my brain hurt.

 

[farlymac]

Thanks guys,
Yes the question was simply whether the tab will clear the dial when screwing the lens onto the camera. If the tab is no bigger than the one found on the Industar-22 then all should be sweet. Nevertheless, I will have a file standing by just in case.
Interestingly, the J-12 I have does not 'line up' when screwed on the Leica, yet focuses beautifully none the less.
I confess that talk of helix(s) and the like make my brain hurt.

Could be someone changed the helix entrance, instead of shimming the lens, and got lucky.

PF

 

[Scrambler]

If the clearance is too close, mount and dismount the lens set to close focus rather than infinity.