Focusing Screen Fungus

mehguy · Aug 3, 2025

I have a Nikon FE with a focusing screen that has a spot of fungus right on the focusing aid.

Is it possible to take soapy water and apply a scrubbing force with a Q-Tip on the aid or will this ruin the screen?

mshchem · Aug 3, 2025

I believe that the screen comes out and is replaceable. I sure would tread lightly. A tiny bit of alcohol + water (vodka like) would be my first choice, realizing that you might ruin the screen. Another thing I would try first would be a dry camels hair brush.

F4U · Aug 4, 2025

I believe I'd use a small artists' brush and a drop of Joy and warm water, then rinse and dip in distilled water. If you go "scrubbing" with anything it will be ruined. BTDT. Don't do anything to it you wouldn't do on a lens. And a lens is glass. This is just plastic. If you have to do a "scrubbing force", it's already etched and no good. Chances are it hasn't come to that though.

reddesert · Aug 4, 2025

The FE focusing screen is removable - IIRC the FM's is not. It is just a single piece of plastic, which is good (for multipart screens you have to be careful about getting anything in between the layers).

I have never ruined a focusing screen with alcohol, but recently I found a plastic focusing screen that I suspect was ruined with alcohol or a similar fluid. While researching another topic (cleaning plastic and rubber woodwind mouthpieces; it also appears to be an issue for people cleaning car headlights), I discovered that if alcohol is strong enough, it is known to attack certain plastics including acrylic. So I would now be real careful about using alcohol on a focusing screen. It apparently depends on the concentration: weak solutions like lens cleaning fluid or 40-50% (vodka) might be ok, but 75-90% (drugstore rubbing alcohol) might be a problem.

skahde · Aug 6, 2025

I have cleaned several screens for the FE-series as well as for the F3. You can put them in 40% alcohol, but just distilled water did it for me most of the time. If the spot is organic it will soften after a few hours and you can try to lift it with the tip of a very fine paint-brush. I don't expect higher concentrations of ethanol to do much at dissolving dry mold, I'd only try this when really desperate. Acetone would be great but the screen would be gone before the mold. And if it is really mold, good luck, as it will have etched a trace into the material anyway.

But why not try to go further, if it is really distracting. You can get a used screen starting from 40 USD on ebay and replace it with an ever brighter K2-screen (adjust meter accordingly, though).

Taking into account it can be replaced you can try even more aggressive chemicals, say our 40% Ethanol and add 2% H2O2 to this or try 6% citric acid. In any event, dont use mechanic force and in the last step rinse with distilled water and remove remaining droplets with a blower, holding it at the edges with clean gloves.

mehguy · Aug 7, 2025

skahde said:
I have cleaned several screens for the FE-series as well as for the F3. You can put them in 40% alcohol, but just distilled water did it for me most of the time. If the spot is organic it will soften after a few hours and you can try to lift it with the tip of a very fine paint-brush. I don't expect higher concentrations of ethanol to do much at dissolving dry mold, I'd only try this when really desperate. Acetone would be great but the screen would be gone before the mold. And if it is really mold, good luck, as it will have etched a trace into the material anyway.

But why not try to go further, if it is really distracting. You can get a used screen starting from 40 USD on ebay and replace it with an ever brighter K2-screen (adjust meter accordingly, though).

Taking into account it can be replaced you can try even more aggressive chemicals, say our 40% Ethanol and add 2% H2O2 to this or try 6% citric acid. In any event, dont use mechanic force and in the last step rinse with distilled water and remove remaining droplets with a blower, holding it at the edges with clean gloves.

The unfortunate thing is, this is the replacement screen

When I obtained the camera, the focusing screen looked dim and damaged in some way, as if you had pressed on the DOF preview, so I did not want to use it in this state that it was in due to potentially bad metering readouts.

I found this screen second hand, not from a camera store or one of those Japanese sellers on ebay however, so it was an independent sale. It looked ok in the photos, but when I put it in the camera, the fungus was visible. Granted it is functional and not dim, unlike the one it is replacing.

I will try to give it a go with distilled water.

mehguy · Aug 9, 2025

I gave it a try with distilled water and after a few hours, the fungus disappeared! Amazing! I'm glad my focusing screen is ok now.

Thanks @skahde for the advice!

skahde · Aug 9, 2025

I wasn't the first one mentioning a solution that would probably have worked as well. Glad it worked and ai take a note in my book for the next screen turning up with dirt on it!

benjiboy · Aug 26, 2025

skahde said:
I have cleaned several screens for the FE-series as well as for the F3. You can put them in 40% alcohol, but just distilled water did it for me most of the time. If the spot is organic it will soften after a few hours and you can try to lift it with the tip of a very fine paint-brush. I don't expect higher concentrations of ethanol to do much at dissolving dry mold, I'd only try this when really desperate. Acetone would be great but the screen would be gone before the mold. And if it is really mold, good luck, as it will have etched a trace into the material anyway.

But why not try to go further, if it is really distracting. You can get a used screen starting from 40 USD on ebay and replace it with an ever brighter K2-screen (adjust meter accordingly, though).

Taking into account it can be replaced you can try even more aggressive chemicals, say our 40% Ethanol and add 2% H2O2 to this or try 6% citric acid. In any event, dont use mechanic force and in the last step rinse with distilled water and remove remaining droplets with a blower, holding it at the edges with clean gloves.

If it was mine I would try some highly diluted hydrogen peroxide .

Focusing Screen Fungus

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