Trouble metering with a Nikkor 80-200 f4

halopes · May 10, 2009

Hi folks,

Im having trouble metering with a Nikkor 80-200 f4 on a Nikon-F camera with a Photomic FTN meter. The readings are way off, resulting in photos overexposed by several stops.

Metering with a Nikkor 50mm f2 gives correct exposures.

I have no idea whats the problem here but the lens seems ok and the coupling prong seems correctly attached.

Any help?

Thanks
Hugo

Rol_Lei Nut · May 10, 2009

Excuse me if I'm asking the obvious, but....

1) Does the zoom have a (non-AI) coupling fork?

2) Are you indexing the lens properly after mounting (the back & forth diaphragm movement)?

halopes · May 10, 2009

Rol_Lei Nut said:
Excuse me if I'm asking the obvious, but....

1) Does the zoom have a (non-AI) coupling fork?

2) Are you indexing the lens properly after mounting (the back & forth diaphragm movement)?

1. The zoom has a coupling fork, but it's a AI fork/lens.

2. I'm pretty sure I'm indexing the lens properly.

I may take the lens to a local shop next weekend or so.

removed-user-1 · May 10, 2009

The Nikon F with a Photomic FTN prism was my first "real" camera.

This may be too obvious (some have called me the master of the obvious), but I always understood the pre-AI (prong) coupling method to be: mount the lens with the aperture set at f/5.6, and then turn the aperture ring to the minimum (say f/22), and then the maximum (f/4 in this case), in order to properly index a pre-AI camera. This was so ingrained in me when I first took up photography that it took me a year (at least) to stop leaving my lenses set to f/5.6 (to say nothing of racking the aperture ring back and forth when changing lenses) after I moved on to a more modern camera.

In any case, if you have not followed the mounting procedure, the 80-200 might not be coupled correctly... all other things being equal. The coupling prong *will* be attached but it won't be indexed until the ring is run through the complete range of stops as described above.

Dave Swinnard · May 10, 2009

Overexposed... Is the aperture actually stopping down to the required stop during the brief instant of exposure? I've seen old lenses with "sticky" apertures that only close down part way during the exposure. Flipping the stop-down lever manually stopped them down, but when actually making the exposure, they didn't close to the set working aperture...overexposure.

Dave

My first FTN is sitting on an island in the remote eastern arctic where my little brother left it. If you find it, I want it back please. (You'll know it when you see it. It's the one that causes you to wonder...why would anybody leave a camera sitting here?)

Rol_Lei Nut · May 11, 2009

rthomas said:
This may be too obvious (some have called me the master of the obvious), but I always understood the pre-AI (prong) coupling method to be: mount the lens with the aperture set at f/5.6, and then turn the aperture ring to the minimum (say f/22), and then the maximum (f/4 in this case), in order to properly index a pre-AI camera.

Setting the lens to f/5.6 was necessary on some older Photomics, but not on the FTn (and F2 Photomics).

halopes · May 11, 2009

I attach/index the lens according to the meter manual: lens is coupled at its max aperture, then I rotate the aperture ring counter-clockwise, and then clockwise. After this is done, the maximum aperture scale on the front of the finder indicates the lens maximum aperture, so I guess everything is ok.

The blades may be somehow sticky or not, I have no idea. Although they seem to close smoothly when I push the actuator on the lens mount. But what really puzzles me is that the meter readings (I mean, without pressing the shutter) are way off. Even readings at the lens max aperture are wrong. On the other hand, if I use a Nikkor 50mm f2 lens, the readings are ok.

Rol_Lei Nut · May 11, 2009

How far off are the meter readings? Is the difference constant at various light levels?

Judging from what you wrote, it shouldn't be a sticky diaphragm, but just try the following: With the lens off the camera, close the lens to its smallest aperture, push the lever which opens the diaphragm and let it go (flick it like that several times). Repeat the test at different focussing distances. The diaphragm should snap shut practically instantly each time.

Does the 50mm meter accurately at lower light levels? (Once a bad contact in my meter switch caused an almost impossible to trace non-linearity).

It *could* be some defect in the Photomic which doesn't let it index properly at f/4.0. Try using your 50mm as a *fake* f/4.0: Mount the lens, but only open it to f/4.0 while indexing, then meter something keeping the aperture at f/4.0 and closing the lens using DOF preview. The value should be accurate.

All in all a pretty puzzle...

halopes · May 11, 2009

The readings are off by 3 to 5 stops, as far as I could check.

It could be a problem with the batteries - I suppose they are quite old. But then again, if this was the problem, shouldn't I get wrong exposures with all lenses?

I'll try what you said regarding the fake f4 with the 50mm later. Anyway, I may drop by a local repair shop next weekend.

nicefor88 · May 12, 2009

The blades of your lens might be stuck at f4, hence the overexposition...

darinwc · May 12, 2009

nicefor88 said:
The blades of your lens might be stuck at f4, hence the overexposition...

/agree.. if the film is over exposed, that is the first thing to check. Set the lens to its smallest aperture, flick the lever and make sure the blades snap closed with no hesitation.

Other possibilities: problem with mechanical linkage... can you try the lens on another camera? Light entering the finder from the eyepeice.. try covering the eyepeice.

Rol_Lei Nut · May 12, 2009

halopes said:
It could be a problem with the batteries - I suppose they are quite old. But then again, if this was the problem, shouldn't I get wrong exposures with all lenses?

Try taking the batteries out and cleaning them and their contacts.

The FTn has a battery check function, which should tell you if the batteries are o.k.

As in my previous post, a bad contact in the meter switch (and possibly elsewhere, like the battery compartment) can give battery test o.k. Higher light level metering o.k. But lower light levels well off (2+ diaphragms)

Maybe the light transmission difference between your f/2.0 and f/4.0 lenses isn't enough for that effect to come into play, but your case seems to merit taking *everything* into account.

If you do get it successfully repaired, please do post here what the problem was!

Best wishes!

halopes · May 13, 2009

nicefor88 said:
The blades of your lens might be stuck at f4, hence the overexposition...

If that were the case, shouldn't I get correct readings at f4?

halopes · May 13, 2009

I'll try another set of batteries tonight.

I'll let you know tomorrow.

Thanks.

halopes · May 14, 2009

I hadn't had the chance to try the batteries but I've ordered new batteries already and I'll try them as soon as possible.

Trouble metering with a Nikkor 80-200 f4

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