Nikon prism glass interchangeable?

[AnselMortensen]

Hi,
Does anyone here know if the glass prism from a Nikon F Photomic is a direct-fit replacement for the prism in a plain F prism?
Thanks!

 

[monopix]

Looking at the assembly drawings would suggest they are different.

https://learncamerarepair.com/downloads/pdf/Nikon-PhotomicTn-Finder-Service.pdf

https://learncamerarepair.com/downloads/pdf/Nikon-F-service-manual.pdf

 

[awty]

I have fitted the prism of a Nikkormat FT into a nikon F eye line view finder.

 

[AnselMortensen]

Thank you for that gem of information!
Was it a drop-in fit?

 

[__Brian]

I believe the prism from the original Nikon F Photomic Bullseye (External CDS Cell) will work. This prism does not have the access ports for the TTL CDS cells. It also uses the same square eyepiece of the original Eyelevel prism.

Reference Only- but Ebay auction has a lot of pictures from angles.

EXC+ NIKON F PHOTOMIC PRISM FINDER, w/CASE, NOT RESPONSIVE TO LIGHT | eBay

NIKON F PHOTOMIC PRISM FINDER "FLAG". This Nikon F Photomic Prism is appropriate for all Nikon F bodies. CLEAR FINDER. w/FITTED NIKON CASE. WITH NICE CLEAN NIKON F CASE. NOT RESPONSIVE TO LIGHT. SHOWS MODERATE SIGNS OF USE, STILL GREAT.

www.ebay.com

 

[AnselMortensen]

Great info, thanks!

 

[reddesert]

I don't know the answer to this. I did look at a plain prism finder and an FTn ttl prism finder through the bottom, and they look different. Of course it's hard to know exactly what you're seeing in a prism because of the hall of mirrors. But the FTn finder has extra facets to either side of the eyepiece, and I believe these are "ears" that reflect light up to the metering cells, which __Brian referred to and you can see in Fig 3 of the Tn finder service manual linked above. So my guess is it wouldn't fit in a plain prism, unless one could decement the ears without damaging it, if that could even be done.

 

[Mamiya_Repair]

This is something that I researched quite a while ago due to the fact that the eye level prisms had a greater value than the FTn finders and the prisms were often showing up in old age with damage. The FTn prism will not work in the eye level finder, it is a little too long. As mentioned, the prism in the original Nikon F Photomic, while slightly different, will work in the eye level finder. The Photomic prism, however, had a small port at the top so that the user could see the light meter needle and this will be very slightly visible when looking through the eye piece.

The Nikkormat prism, while seeming like a good idea due to low price of these bodies, will not work as it had a different mounting scheme on the bottom of the prism (one base ridge as opposed to two on the Photomic prism).