Rolleiflex Prism Finder - Fixing a Loose Prism

I recently acquired a Rollei 90 degree prism finder for my 3.5F. It was listed as spares or repair as the prism inside was loose, also there was what turned out to be balsam separation. Here's how I decided to fix the looseness.

 

 

Remove the four tiny screws and the top housing just lifts off (I think the screws are under the leatherette covering on some models).

 

 

The prism is retained by two metal strips on either side, held by longer screws..

 

 

I cut two thin strips of rubber, actually from a lens grip, and trapped them under the metal retainiing strips. After tightening the screws, the prism isn't loose anymore.

 

 

 

A perished piece of foam inside the housing top was renewed, and the top replaced. Getting the screws back in is tricky.

 

 

This is the balsam separation, it's visible in use but not too obtrusive, being near the edge.

 

It's not clear why the prism was loose or whether there was foam or similar under the retaining strips, which were found tightened down. Perhaps just replacing the perished foam at the top might have done the trick, but my solution seems more secure.

 

To be honest, I was a little disappointed with the prism in use. Viewing through it seems to make the image look dimmer than just using the waist level finder. But there you go.

Edited November 14, 2020 by John Seaman

Had another try with it on the 3.5F and perhaps I was being unfair. It doesn't really dim the view that much, it just seems dull compared with (say) a 35mm SLR. My biggest problem is, being a left eyed photographer, I'm accustomed to the camera body blocking my right eye. With the Rollei prism unless I close one eye, I'm seeing through the prism with one eye, and directly with the other, causing confusion between the two views in my poor old brain.

Nice!

Just a thought: Old deteriorated foam is often blamed for prism de-silvering. Nikon F prisms comes to mind. Nikon began placing a protective piece of material between the prism surface and the foam in later models.

In this case it appears as if there is a black material protecting the silvered surface — is that correctly observed?

Yes, you don't see the actual glass / silvered surface except at the eyepiece position. It's protected by some kind of coating or sheathing, I was a little scared to disturb it to find out exactly what it was. The foam was perished to a powdery rather than sticky consistency. I once opened up an old Canon SLR and found that contact with sticky foam had eaten away the prism silvering.

Had another try with it on the 3.5F and perhaps I was being unfair. It doesn't really dim the view that much, it just seems dull compared with (say) a 35mm SLR. My biggest problem is, being a left eyed photographer, I'm accustomed to the camera body blocking my right eye. With the Rollei prism unless I close one eye, I'm seeing through the prism with one eye, and directly with the other, causing confusion between the two views in my poor old brain.

Please accept sympathy from another shooter with a dominant left eye. I can't think of a camera that favors types like us. Can you?

I recently acquired a Rollei 90 degree prism finder for my 3.5F. It was listed as spares or repair as the prism inside was loose, also there was what turned out to be balsam separation. Here's how I decided to fix the looseness.

 

[ATTACH=full]1364651[/ATTACH]

 

Remove the four tiny screws and the top housing just lifts off (I think the screws are under the leatherette covering on some models).

 

[ATTACH=full]1364652[/ATTACH]

 

The prism is retained by two metal strips on either side, held by longer screws..

 

[ATTACH=full]1364653[/ATTACH]

 

I cut two thin strips of rubber, actually from a lens grip, and trapped them under the metal retainiing strips. After tightening the screws, the prism isn't loose anymore.

 

[ATTACH=full]1364654[/ATTACH]

 

[ATTACH=full]1364655[/ATTACH]

 

A perished piece of foam inside the housing top was renewed, and the top replaced. Getting the screws back in is tricky.

 

[ATTACH=full]1364657[/ATTACH]

 

This is the balsam separation, it's visible in use but not too obtrusive, being near the edge.

 

It's not clear why the prism was loose or whether there was foam or similar under the retaining strips, which were found tightened down. Perhaps just replacing the perished foam at the top might have done the trick, but my solution seems more secure.

 

To be honest, I was a little disappointed with the prism in use. Viewing through it seems to make the image look dimmer than just using the waist level finder. But there you go.

Trying to find a prism in good shape for a reasonable cost is like finding hen's teeth! Nice job