Nikon f90x and aperture readings

dugrant153 · Jul 3, 2011

So i just bought an f90x nikon slr and thought it was working great until i realized something. When in Av or program mode, whenever i turn my aperture ring from say f1.4 to f16, the meter will read properly the correct shutter speed. However, when i turn the aperture ring the other way, the meter seems to be locked in f16 or whatever was last set before turning the ring the other way.

Right now i have to use M mode and use a handheld lightmeter. Works fine in M mode from what i can see.

Any help would be greatly appreciated!!

PhotoJim · Jul 3, 2011

Sounds like a sticky AI coupling ring. If you remove the lens you'll see the coupling ring tab at the 2:00 position (camera on its back, prism at top). If it's been bent or is sticking, it could act precisely as you've described although it should do this in manual mode too. You can verify my theory by watching the tab with your lens mounted. If you turn the aperture ring, the tab should move along with the ring (it latches onto the AI coupling tab when you move the aperture ring in one direction, and returns under spring tension when you turn the ring the other direction).

CGW · Jul 3, 2011

Any chance the return spring on the AI tab ring is busted? Since the tension of that spring isn't exactly light, I'm wondering whether "sticking" is really the problem. Worth a look?

PhotoJim · Jul 3, 2011

My tab was bent once and it acted as the poster described, so that was my first theory, but a spring issue is also possible.

CGW · Jul 3, 2011

PhotoJim said:
My tab was bent once and it acted as the poster described, so that was my first theory, but a spring issue is also possible.

Mentioned it since I saw one a few years ago at a PHSC fair in Toronto with this problem and diagnosis. Could be the same here?

LyleB · Jul 3, 2011

If it was a sticky or bent coupling ring, wouldn't it happen with more than just this one lens?

PhotoJim · Jul 3, 2011

LyleB said:
If it was a sticky or bent coupling ring, wouldn't it happen with more than just this one lens?

Not necessarily. Some aperture rings are tighter to the mount than others. If the ring doesn't contact the AI tab as tightly, a weak spring or a slightly bent tab might still work acceptably.

Shawn Rahman · Jul 3, 2011

Presuming it is not bent, but it is sticky, can anyone suggest a home remedy? I have the same problem with one my Nikons.

dugrant153 · Jul 3, 2011

So it seems like a sticky Ai coupler. I move the aperture ring one way to f22 and its fine. Then I move it back but the ring stayd stuck - i can tell with the little tab since it stays still.

I move it manually with my finger with no lens mounted and its fine and always returns so I think my spring is fine. Maybe i need to lube the ring with oil?

dugrant153 · Jul 4, 2011

PhotoJim said:
My tab was bent once and it acted as the poster described, so that was my first theory, but a spring issue is also possible.

How did you end up fixing this?

Not necessarily. Some aperture rings are tighter to the mount than others. If the ring doesn't contact the AI tab as tightly, a weak spring or a slightly bent tab might still work acceptably.

After messing around with my two nikon lenses, I found that one lens causes more of a problem than the other, but both end up causing the problem. Sounds like the Ai-coupling ring has resistance on it as I manually push and pull it.

Thinking of just picking up another F90X body... aiyah... but hoping not to go there if I can avoid it. Maybe if I can mount non-Ai coupling lenses on this camera I'll be fine. Or shoot in M mode with a light meter (seems to work!).

markbarendt · Jul 4, 2011

dugrant153 said:
Thinking of just picking up another F90X body... aiyah... but hoping not to go there if I can avoid it. Maybe if I can mount non-Ai coupling lenses on this camera I'll be fine. Or shoot in M mode with a light meter (seems to work!).

I actually have 4 N90s bodies. Two are true beaters with real quirks but handy in M-mode hip deep in a river or any place where you might not want a nice camera.

Actually prefer M-mode 99% of the time.

If my good ones died though, I'd just get a bargain body from KEH. Might even get an F100.

dugrant153 · Jul 4, 2011

markbarendt said:
I actually have 4 N90s bodies. Two are true beaters with real quirks but handy in M-mode hip deep in a river or any place where you might not want a nice camera.

Actually prefer M-mode 99% of the time.

If my good ones died though, I'd just get a bargain body from KEH. Might even get an F100.

Actuually... I too also quite prefer M-mode with my sekonic l-308s light meter. Makes for great exposures (versus having to exposure compensate up and down and up an down...).

I think the rest of the camera is in great working condition (although looks pretty used) and the internals seem to be intact and working very strong. If it's just the Ai-coupling... I think I might be okay here Maybe just shoot M mode and call it a day.

John Koehrer · Jul 4, 2011

NO OIL! A drop of alcohol andor two working the ring could help. If one application helps try a second.
If you want adventure, the ring is held on by the lens mount, if you're willing to go exploring there may be enough dust in there to slow it down.
Keep the camera laying on it's back and work carefully as I recall the coupling ring like to pop out of position.

PhotoJim · Jul 4, 2011

dugrant153 said:
How did you end up fixing this?

This was several years ago when my F90 was only a year or two old, so I sent it to Nikon for repair. It wasn't cheap but the cameras was in perfect condition otherwise so I wanted to get the work done.

My instinct is that an independent shop could do it economically. I'm a big fan of getting cameras serviced because repair shops will clean them up and adjust them and they'll tick along for many more years. The less uncertainty, the better.

Nikon f90x and aperture readings

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