Nikon FG20 prism cleaning

[mercedes_sl1970]

Hi there

I have a Nikon FG20. The prism is quite dirty and the foam against which the mirror rests is starting to break down. Otherwise, the camera is in excelllent condition. I was wondering if anyone has had any experience with dismantling the camera to access and clean the prism, and, to replace the foam? Perhaps there may be a similar approach to other Nikon models?

Thanks

Andrew

 

[John Koehrer]

mercedes..........
There are only two surfaces to clean on the prism. One is above the focusing screen the other is just in front of the eyepiece.
I have always used a bird's (goose,duck) feather cleaned in alcohol to remove the oils to clean surfaces like this and it doesn't leave lint. It also works well for the mirror.
Getting to the prism surfces is a little more complex though. The eyepiece surface you'll need to remove the top cover. The bottom suface you would either remove the focusing screen or the prism itself.
I'd suggest just cleaning the focusing screen with the aforementioned feather & let it go at that.
The foam can be had from Microtools or Jon Goodman who I believe is somewhere on APUG.

 

[DBP]

You can also use selfadhesive craft foam, available at any art supply place. Unless it has developed fungus, there is unlikely to be a need to clean the actual prism. Just clean the focusing screen and eyepiece, and, if absolutely necessary, the mirror.

 

[mercedes_sl1970]

John and DBP - thanks for the advice. The suggestions about foam are appreciated - I'd forgotten the name of Microtools and hadn't thought about craft foam - excellent idea.

I'll have another go with cleaning the focusing screen. What has happened there is that flakes of degraded foam have smeared into the focusing screen. This was after using a blower, camel hair brush and then lens cloth... Any suggestions on a solvent which would break down smeared flakes of degraded foam? I've tried a lens cleaner to no avail.

Andrew

 

[John Koehrer]

Andrew,
since it's that goop on the screen two things I'd try.
Gently use a bamboo skewer to try picking off some of the bits and then wrap the tip of the skewer with a small bit of cotton from a Q-tip dipped in alcohol and squeezed almost dry. The key is all about control and patience.
I've also used dental probes with an offset tip to pick that stuff out of the grooves. Wasn't perfect but didn't have to replace the screen either.

 

[mercedes_sl1970]

John - will try your suggestion. Thanks for taking the time.

Andrew

 

[DBP]

Has anyone tried "Goo-gone"? I know if will remove the foam residue, but is it safe for the focus screen?

 

[pelerin]

Has anyone tried "Goo-gone"? I know if will remove the foam residue, but is it safe for the focus screen?

Many screens are not simply ground glass. Some are laser etched, others have molded plastic surfaces. Applying pressure can deform the "ridges" that make up the surface of the screen. This will result in dark areas on the screen that can not be cleaned. If I were going to use a solvent product to clean a plastic screen I would remove it from the camera and try a tiny bit on an out of the way spot first to determine compatibility.
Celac.

 

[Mike Kovacs]

I would steer clear of regular foam and contact "interslice" on ebay, aka John Goodman. He sells nice kits and will provide after sales support if you run into problems installing it.

His foams are high quality - they don't outgas (fogging optics) and should be resistant to the type of breakdown the factory foams exhibit.