Schneider 120mm for 4X5

[Huck]

I tried to clean my 120mm Schneider lens today. I used Eclipse cleaning solution with a stick of sensor cleaner on the rear element of the lens. To my surprise, what seems to be black paint came off the lens, and the cleaner got all black. Is the rear element of Schneider lens coated with some sort of black coating? There were lots of smears on the lens from what seems to be black coating. I tried to wipe it with a regular lens cleaning solution and got almost everything off the lens. Is this normal?

 

[Tom1956]

There's no black substance on the lens from manufacture. Sounds like you're smearing the black paint from the lens ring onto the lens and getting confused as to where the black stuff came from. Unless some boob in the past got or put black paint on the lens.

 

[Dr Croubie]

There's no black substance on the lens from manufacture. Sounds like you're smearing the black paint from the lens ring onto the lens and getting confused as to where the black stuff came from. Unless some boob in the past got or put black paint on the lens.

There's definitely a school of thought that advises to "fill in" deep surface scratches with black paint/felt-tip etc. The idea being that light reflects and refracts weirdly around scratches, gives huge flare and lowers overall contrast. Filling in these scratches with black paint stops the flare but might show up as a very faint dark spot on a photo (depending on location on which element of course). So there might be some paint from one of these "fill-in" jobs.

Or yeah, you're just cleaning the paint off the rim and smearing it off the glass (or you're cleaning off the bits left by the guy before you who did that).
I'd suggest get a Lenspen or two, they'll clean anything off the glass (except coatings), leave no residue, and won't touch the rim paint.

 

[Newt_on_Swings]

I've had that happen before, and it was from the paint around the lens that was painted. Eclipse solution also removes sharpie too, something that is used for small touch ups such as on retaining rings that might have bright marks from tools slipping.