Yashica Mat 124G | Polishing Rear Element w/ Cerium Oxide

[justtorchit]

A few years back I picked up a really nice condition Yashica Mat 124G from one of our local camera shops for a fair enough price. I wasn't looking for one but this one was just so clean and the price seemed very good considering what was available at the time. I got it home, ran a roll or two through it and promptly put those rolls in my "to-develop" pile of film....where it has sat with a number of other rolls still to be developed. I have something of a backlog at this point, haha.

Well, the other day I was tinkering with the camera itself, and having no film in it, fired the shutter on B, and looked through the optic and noticed an optical ailment, haze or etching from fungus perhaps? Maybe lens separation? From everything I can see, it appears to be right on the back of the rear-most element. I keep turning the lens in my hand, and using a flashlight to illuminate the issue, trying to detect if it's between elements but it very much appears right on the back element.

So I still have yet to develop the rolls of film from the camera, which at this point, are inseparable from the rolls to be developed from my other medium format cameras. I have a feeling, many shooters would suggest first look at the images from the camera and see if this lens issue has any effect on image quality. At most, I imagine it would be a loss of contrast (if even only slight). And the risk of ruining the lens could be greater as finding a replacement would likely result in buying a whole other unit.

The OCD in me really wants to see if I can clean the element and I was wondering if anyone has experience or could weigh in on their thoughts about using some cerium oxide to polish that rear element. Is it coated? I can't tell. It appears flat but I could be totally missing a nuance. Would polishing this even do anything? The issue seems like pitting, which could be far deeper than the human eye perceives and I realize taking too much off begins to alter the optical formula. Does anyone have any thoughts on this? Maybe more explanation on what I am seeing? I appreciate your time!

[aidaho]

My experience with cleaning lenses can be summed up with: if you need a flashlight to see contamination, cleaning attempt is going to be a waste of time.
This is why I no longer use a flashlight. Makes me sleep better at night.

[visualopsins]

Cerium oxide polishing would probably be my last choice before throwing it in garbage. There are plenty of other cleaning methods to try first, such as plain water, then mix with a little soap, then try alcohol, then lighter fluid, then acetone, of course stopping if any of those methods are successful. Gentle heating and cooling may heal separation; very gradual and gentle to prevent uneven thermal expansion and contrsction, which will fracture the glass. A little cigarette ash makes a good lens polish. Last resort -- cerium oxide...

[justtorchit]

aidaho

haha, yes. Admittedly, the only reason I first saw this was because I happened to be looking through the back of the camera and the lens was catching some direct sunlight. If I only I had never looked!

visualopsins

Thank you for this - good points! Step up the efforts rather than go straight to the most drastic. I think I subconsciously looked at this and assumed the usual methods weren't going to work but it would be foolish of me not to try them. Thank you for these suggestions!