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[Natew]

Hi!  I've got a Mamiya C3 that my dad got before I was born.  It's not been used since ball park 40 years ago, either.
 
I expressed an interest and my dad let me at it.
 
What I've discovered, though, is that the lenses I've got w

[Rick_oleson]

It looks like your problem, as you say, is internal to the rear cell.  This may not be real good news, as there is no way for dirt or oil vapor to have gotten in there, so it may be deterioration of the coating or cement.  I don't have any C len

[Paul Ron]

You will have to open the lens, take off the front n rear cells n see if the dirt can be cleaned. Don't mix up the viewing n taking lenses n don't lose the shims.  
 
I hate to say this but what I see in your pics may be fungus. Hard to tell for

[Jaywarner]

I'm the guy who lent Natew the Mamiya, and I resent that 40 year bit.  More like 30, or 25 years.  What was the expiration on the old film it had?
 
As for pulling apart the lens to clean it, I agree with Paul_ron:  Keep the pieces associated

[Natew]

Yep, that's him right there, my dad.

  And I think there's a point to the less than 40 years. (I forgot the expired film in the case! 1991...)
 
Thanks to everyone f

[Mikel]

It's difficult for anything more than a wild guess.
 
The viewing and taking lenses may be identical and interchangeable; it was done in the 50's and 60's on several brands of TLR's. I have no idea about the Mamiya.
 
The only important

[Natew]

Mikel-
 
I did a somewhat poor job of describing where the problem was: from the rear of the lens, talking by surface number (i.e.: 1 is the most readily available surface), the problem is on surface 3 (not directly adjacent to anything but the g

[Rick_oleson]

The durability of lens coatings varies dramatically.  With some, the first touch ruins it - some are harder than the glass under them.  I have a Kowa lens that had a badly fogged coating, the cause of which I don't know - while I would not have done

[Mikel]

Nate-
 
In reviewing some of my earlier notes, it appears very possible that the Mamiya C Series TLR lenses are interchangeable between viewing and taking lenses.
 
As for the last resort method of cleaning lenses, it was a desperation metho

[Natew]

Thanks Rick and Mikel!  I'll put your comments to good use.
 
Here's the plan at this point: as long as my dad agrees, I'm thinking to try a little polishing.
 
My wife was a glass engineer in a previous life (automotive glass) and had s

[Paul Ron]

I've swapped viewing lens for taking lens. The coatings are different, the focal lengths are the same. You'll have to adjsut the film plane to view screen again in order to get crisp pics. You'll pick up some flare but with carefull attension to y

[Mikel]

That's right- it's a last resort kind of thing.
 
I hope everyone who reads this understands it.
 
If the glass is already etched, there is little left to lose. It's up to you. It worked for me.
 
BTW I'm going to meet the chemica

[Jaywarner]

OK, we've gone past the point of planning to do a full restore on the lens.  Does anyone know a professional camera repair person who might know how?  And hasn't retired?  Natew - any idea what a replacement lens might go for on-line?  In case nothi

[Paul Ron]

There are plenty of hobbiests that do this sort of thing all the time. Professioanls, there are a few n charge way too much concidering a used lens in good shape is only $120. Pay someone $100 to do a CLA on a fungus lens, not worth it sicne they won(

[Natew]

OK, so after being so busy, I finally got to working on this.  Here's the post-work picture to date.


 
 
Operations performed so far:
* Removal of rearmost