front cap sizes - Jupiter 8/12

[Apostata]

Hello! Long time no chat.

Would anyone know what the front lens cap diameter for a Jupiter-8 is? I believe they list them here, but 49mm doesn't make sense if the filter size is 40.5mm - that's quite a discrepency. The cause of my confusion is that I recently purchased a Skylight filter for both the J-8 and my new Jupter-12. The original cap on the Jupiter-8 still fits semi-snuggly enough on both (with the filters attached), so I'd like to get an identical one for the J-12. Would anyone know the definitive diameter of this cap? I've been thrown freebie caps that come in every size *but* the one I need, so - tired and weary - I'm looking for truth (!) 🙂

Much appreciated.

Matt

 

[pshinkaw]

My black LZOS Jupiter-12 uses a 40.5mm screw-in cap.

Be aware that some metal screw-in caps may have slightly different pitch tolerances than others. I bought some metal 40.5mm screw-ins from Filter Connection that do not fit well on some of the finer threaded Mamiya lenses I have. They fit fine on Soviet lenses.

-Paul

 

[Apostata]

Thanks Paul - I should've specified that the Jupiter-8 cap is a push-on rather than a screw-in. Would this affect the size?

 

[rbiemer]

I've had two J-12s and they each had a different lens cap; one had a metal cap that fit over the central part of the lens(where the filters screw into) that was the same size as caps for my J-8. Fit well but was sometimes a pain to remove--I couln't get a good grip on it unless the lens was focused close. The other had a plastic cap that fit over the entire front of the lens but didn't stay on very well. Don't know if either was "factory original" though the plastic cap had the same logo as the lens. Not sure what size the plastic caps was.
Rob

 

[zuikologist]

I've just measured the cap on the J12 on my desk (in the office!). It looks like a slip-on 50 or 51mm inside diameter cap.

 

[pshinkaw]

A slip on (or over) cap is usually 1-3 millimeters larger than the screw-in thread. It can vary because of the differing thickness of the metals used by different manufacturers.

My Jupiter-12 has a threaded 40.5mm portion and a separate outside ring that is much larger. Thus, while it will take 40.5mm screw-in accessories, a slip-on cap could be as much as 10 miilimeters larger. I have never tried to fit one, so I don't have an exact size for you.

If you use a slip-on and it is slightly too large, you can apply Dr. Scholes Moleskin to the inside lip to give it some grip (doggeral unintended). I have done that on the chrome plated Jupiter-8 caps that were loose.

My favorite overall cap is a 40.5mm Nikon or Nikkor cap with the sping-loaded buttons. They were original equipment on Nkon enlarging lenses and Nikkorex movie cameras. They have a strong grip, and can be removed easily. They can sometimes be found in odds-and-end bins in camera stores. I recently bought a new one that way.

Another good source is the plastic back cap for a T-mount lens. Most of them are black polyethylene and get discarded when the lens is attached to a T-mount adapter. Since a T-mount male thread is 42 millimeters it almost always fits as a slip-on over a 40.5mm lens thread.

-Paul

-Paul

 

[Bob L]

All of My J-8 uses a 40.5 mm snap cap and 2 of my J-12 uses a 49 mm snap cap.

 

[airds]

loose lens caps? easy solution

loose lens caps? easy solution

If you use a slip-on and it is slightly too large, you can apply Dr. Scholes Moleskin to the inside lip to give it some grip (doggeral unintended). I have done that on the chrome plated Jupiter-8 caps that were loose.

-Paul

A bit of Jon Goodman's self adhesive light trap felt/foam in the smaller size will do the same trick. It's also very good for (re)lining lens hoods, being anti-reflective.

rdgs


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