Differences in two Jupiter 8 models.

Aquanaut

Aquanaut

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Hello Brian,

Is it possible to swap the front elements on the Jupiter8.

I have a great alu one with the tab but the front is extremely marked with cleaning scratches. It is really terrible.

I bought another one, a black one with a good front element, but this turns when I focus the lens, not like the alu one which stays in the same position.

Are the optical elements the same in these two models?
 
The diameter of the front element of the earlier 1950s J-8's is slightly different from the later ones. The entire optics module can be swapped out. So if you like the feel of the Tabbed aluminum focus module, you can replace the entire module with the one from the Black J-8. Once you start taking the elements out of the optics module, you will probably find (like i did) that they are different. I tried...
 
I don't think I'll bother changing. I would still have the diaph ring which turns when focusing. Guess I'll just have to got along with that.

Thanks anyway Brian.
 
If you transfer the optics module from the Later Black J-8 to the older focus mount the aperture ring will stay in position while focusing. It will still have two scales, so what I do is to swap out the aperture ring. You will need to properly shim the optics module in the new mount, and index the aperture ring to the proper position. Not hard to do- but you need to be able to test focus. You can use a negative strip at the back of a film camera with an back that opens for this.

Some how to is on Kim Coxon's site.:

http://pentax-manuals.com/repairs.htm
 
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