Topic: Jupiter 37A infinity mod

Hi there, here is my 2cents...

I am using Pentax DSLR and I play with m42 lenses, Russian made mostly as they are low cost but not 'cheap', I always have problem with the adapter, those 'flush fitting' adapter that allows infinity focusing is hard to install and remove, quite trouble when I need to change lenses in middle of shoot, so I decided to stick with the non flush type, but I only able to do close focusing then, there is exception with mirror lenses, as they focus pass infinity (compensate for temperature change), more than enough to offset the adapter thickness.

Just recently I pick up a Jupiter 37A, which is a very sharp 135mm lens, with non flush fitting adapter I can only focus to about 20m, after looking at the inside of the lens I found a simple way to push the 'infinity lock' further, and this is completely reversible, but by doing so the focus scale will become out of line, I think that wouldn't be a problem, as we will focus by eye or use AF assist anyway !

Here is how to do it 'at your own risk !'

Simply remove the m42 mounting at the back of lens which locked by 3 screws, after that you will see two L-bracket at the sides of the lens assembly, they are used to limit the optical block from completely unscrew from the lens body. Remove only the 4 screws that holding the L-brackets, then turn the focus to the far end, so that the L-brackets shifted by one hole, that little adjustment moves the optical block further to the focal plane, thus bring the lens into near infinity focus. Put back only one screw at both L-brackets, or you can drill holes for the other screws but not necessary, put back the m42 mounting that's all !

http://www.joelee.ws/pic/j37a-1.jpg
http://www.joelee.ws/pic/j37a-2.jpg

I am still looking for ways to adjust my Mir 1B, Pentacon 30mm/3.5 and Pentacon 135mm/2.8 any idea ??

Do you Yahoo ? No I hiccup only:P

Re: Jupiter 37A infinity mod

I had one of this J37, 20 years ago ; I confirm it was my best 135mm lens !   I hope your modification is working correctly .    With this   focal , the right  focus  is far easier to obtain  than with a shorter one   .  One can buy adapters for   few money ,  Thus I think it's better to buy them than to modify the lens

I am a Pentacon and kiev( MF and35 mm) user,and also :contaxII,III,IIa  ,contaflex , contarex bullseye ,voigtlander ....

Re: Jupiter 37A infinity mod

Adapter for Pentax is particularly trouble to use, due to the large back focus distance of Pentax, a conventional adapter won't allow focus to infinity, and the correct type must be mount and lock 'inside' the body, that made lens changing very trouble.

Do you Yahoo ? No I hiccup only:P

Re: Jupiter 37A infinity mod

Maybe , this can help you :
"Using Older Lenses with PENTAX DSLRs

Q: Can I use older PENTAX lenses on my DSLR?


A: Yes. (These steps may vary slightly depending on camera model). PENTAX A-series lenses (with an "A" setting on the aperture ring), can be used as manual-focus lenses in all exposure modes on a PENTAX DSLR. PENTAX K-mount, M-series and S (screw) mount lenses without auto-aperture control (an "A" setting on the aperture ring) can be used in Manual exposure mode using stop-down metering and manual focus. This is the exposure mode which will give accurate exposures when using these older lenses on our digital SLRs. If older lenses without an "A" setting on the aperture ring are used in Av (Aperture Priority) Mode, an exposure error may occur. Note: Using PENTAX S (screw) mount lenses on a PENTAX DSLR requires the use of a Pentax Mount Adapter B. To set up your PENTAX K10D, K200D, K20D or K2000 to use older PENTAX lenses: Press the Menu button

I am a Pentacon and kiev( MF and35 mm) user,and also :contaxII,III,IIa  ,contaflex , contarex bullseye ,voigtlander ....

Re: Jupiter 37A infinity mod

Thanks, exposure wouldn't be a problem as the camera will handle it in stop down mode, but focusing can't be done with the camera settings alone.

Do you Yahoo ? No I hiccup only:P