Looking for replacement rear lens element for an older Mamiya 6

[keithostertag]

I recently bought an old version IV (I think) Mamiya 6, which I have always wanted and it was only $20! Unfortunately after getting it home I discovered I did not look at it closely enough and there was lots of fungus inside the lens. I suppose I am lucky the fungus was only on the outside of the rear element, but after cleaning it with a mix of hydrogen peroxide and IPA it still left etching on the glass/coating. Real bummer.

If any of you could spare one from your cache of donor Mamiya 6's I would really appreciate it. USA.

Thanks,
Keith

 

[WoodallP]

Hi, its probably worth specifying the lens, I think there were a few over the years.

 

[TenEleven]

Also you'd be much better off replacing all the elements if you get a donor camera anyway. The elements are matched to each other at manufacture.

Yes it is mechanically possible, to screw in another cameras rear lens.

However, it is extremely unlikely that the focal length (aka infinity setting), optical performance, etc. will be as specified.

I have tried this a couple of times with an also unit-focusing 3/4 lens (Tessar type) Fujica super six before and even the closest matched element out of the four I had on hand still came at a big penalty in the overall performance - the corners never got as sharp as before - even at f/11 they were visibly soft at very slight enlargements.

In the end I settled with a lens that had "cleaning marks" on the front (changing over the entire thing into the good body) it did not quite look as mint, but at least by f8 things were sharp.

tl;dr - in my experience Tessar types are especially picky about having the correct rear group.

 

[keithostertag]

Thanks, I guess I hadn't realized that with these older models there would have been more than one lens supplied. As far as matching the elements... well I had not thought of that either though with a $20 camera I won't be too picky. The camera serial number is 89000.

 

[TenEleven]

If it's just one side and the coating is affected but the glass isn't (or it's very shallow) you could also - as a hail Mary - try to polish the coating off entirely.
I have done that and it has improved what would be basket case lenses otherwise. I used "Flitz" but I guess brasso or anything else that's just mildly abrasive would work.

In fact one of these lenses where I did this for the front element is now among my sharpest ever.

 

[WoodallP]

And it was still a bargain!

 

[keithostertag]

Yes, it was a bargain especially after I spent two hours getting the focus mechanism unstuck ;-)

I have read various anecdotes both good and bad about attempting to polish the offending etching out- I may try that since otherwise neither the lens nor the camera is usable as-is.

Anyway, if any of you could help me out with either the rear element or a complete lens I would greatly appreciate it. Just PM me.

Thanks,
Keith

 

[Phil_F_NM]

Cerium oxide is super cheap in paste form. A tube of it will last you forever.
Phil

 

[rfaspen]

I can't tell, but maybe that's mostly affecting the coating only? If so, SonnarBrian's suggestion to polish is definitely warranted.

In general, I hate fungus in optics!