Nikon F Prism Question.

snegron · Apr 4, 2007

I recently purchased a standard prism form my Nikon F. It came with the metered FTN prism, but I wanted to get the standard prism for it. The standard prism fits well, however, when I put the FTN finder back on I noticed that there is a small gap (maybe 1/32") between the prism and the body. I never really noticed if this gap was there before. Is the FTN prism head supposed to fit tight without any sort of gap? I will try to post a picture to show what I mean.

I know this doesn't affect picture quality in any way, but I am concerned that it might not be fitting properly on the body and I would hate to drop the metered head due to lack of proper fit.

snegron · Apr 4, 2007

This is the first time I download an image on Apug, so I hope it works! The gap is visible between the left front side of the prism and the top panel of the body.

John Koehrer · Apr 4, 2007

Snegron,
That's pretty typical of a metering head on an F. You may note a bit of springiness when you press down on the meter head also, That's also normal. I don't know if you're familiar with the earlier meter heads, but they didn't have the clamp on the front that grab the corners of the nameplate. I think Nikon did that because more than one person had the meter pop off in while working.

snegron · Apr 4, 2007

John Koehrer said:
Snegron,
That's pretty typical of a metering head on an F. You may note a bit of springiness when you press down on the meter head also, That's also normal. I don't know if you're familiar with the earlier meter heads, but they didn't have the clamp on the front that grab the corners of the nameplate. I think Nikon did that because more than one person had the meter pop off in while working.

Thanks! Those front clamps don't seem to fit all that great either. The one on the side nearest the shutter release button snaps into place really well, but the other one doesn't. I thought that maybe there was something wrong with the metered prism head (the standard prism fits like a glove), but all edges are straight and there is no sign of damage anywhere. I was starting to wonder if the nameplate was the problem. I have heard that Nikon changed the nameplate with F models during the mid 60's so that metered prism head clamps could latch on to the bottom of the nameplate better. Maybe this nameplate was not cut right from the factory or is bent (doesn't appear to be bent or damaged though)?

fparnold · Apr 4, 2007

No direct answer, but my first prism for my F was a photonic, late 60s vintage, which couldn't couple correctly with my F, 64xxxxx serial number. I gave up and swapped it for a straight prism (which in the late 80s was a 1:1 swap for no extra money). The behaviour you're seeing sounds very familiar, though mine would never snap in at all, it just fit, and stayed loose.

Jim Jones · Apr 4, 2007

There is a problem in using Photomic finders on very early Nikon Fs. The rear of the well into which the focusing screen drops is too high on each side of the eyepiece. This has to be filed down to about level with the top plate accomodate the Photomic finder. It's a simple job, but one has to be careful to keep filings out of the camera interior. Serial numbers up to 6700000 require this.

resummerfield · Apr 4, 2007

Also, check the foam in the back well, under the prism eyepiece. It's an easy fix to replace.

ehparis · Apr 5, 2007

With new foam both my 1960's "Nippon Koguku" model and mid-1970's model have very tight fits with an FTn finder. To qualify, as has been stated elsewhere, the early model has been factory modified so that, like the famous reddot models, it will properly fit an FTn.

I primarily use the standard, eye level prism so had to double check this to be certain my memory was correct. The "reddot" models are discussed on the mir.com and other sites as to the serial number range and their use being to show they were properly made to be fitted with the newer phototomic models.

I've yet to see a Nippon Kogaku model F that will properly handle a finder like the FTn unless it is a red dot or is known to have an adjustment made so the finder will fit correctly. That's the whole point of the red dots.

snegron · Apr 5, 2007

The serial number on my F starts with 7292... (no red dot though). The small foam under the eyepiece looks a bit worn, but I don't think this is what is affecting the fit. The prism currently sits well near the eyepiece but is raised in front near the nikon logo. My guess is that if the foam were newer (or thicker), then it would cause that much more of a gap (probably an even or level gap though). Since the FTN finder has to cover, or go over the nameplate logo (unlike the standard prism that fits behind the nameplate), I think any deformity in the nameplate would cause an uneven fit with the prism.

The confusing part is that when I remove the metered prism and inspect it, it appears to be perfectly straight at every angle. The body and nameplate also appear to have perfect angles. It's only when I combine the two that they don't appear to fit properly.

snegron · Apr 5, 2007

I fixed it!!!!

There were two loose screws under the prism head near the front where the prism appeared to be higher causing the gap. I tightened them and now the prism has a near perfect fit! There is a very tiny gap, just about enough to fit a paper through but not as deformed as before. I am very happy now!

mawz · Apr 5, 2007

Note the Red Dot models were only cameras that shipped with the eye level prism. Non-Red Dot models of similar vintage were ones shipped with metering prisms. It's only the pre-Red Dot era models that needed the modification

Nikon F Prism Question.

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