Nikkormat FT2 meter reading many stops high??

Not long ago, I replaced the battery in my Nikkormat FT2 because the meter was seemingly not working, so it has a new silver oxide cell installed (as of about July of this year, and the camera has barely had the meter turned on in that time).

I've noticed, though, that the meter is reading MANY stops high. I've checked that the aperture ring was turned to wide open immediately after mounting the lens, the film speed setting is correct (EI 50, using up some "defective" Macophot I got cheap/free several years ago and took out of the freezer early this year) and the in-viewfinder shutter speed display matches what's set on the lens mount. With the shutter at 1/500 and the aperture at f/5.6, indoors, the meter needle goes "+" as soon as I move the advance lever to activate the meter.

I know this meter was working correctly for (at least most of) the life of the first battery cell I put in the camera, which was a zinc-air hearing aid battery (I didn't know at that time that alkaline or silver oxide would work correctly in this model).

Am I doing something wrong, or do I need to get under the hood?

Faulty CdS photocells can do that. Fortunately, the galvanometer is still functioning, because the odds of your finding a suitable replacement photocell are a lot better.

Set ISO 125, 1/125 shutter, and meter a clear blue sky, and the reading should be 'about f/16'...the birghtness of the sunny sky DOES vary from the sunny 16 rule of thumb! If that result is not what you get, the meter is malfunctioning.. The issue might be that the potentiometer (whose value changes with aperture/shutter) could have some oxidation on its surface. You might try changing shutter & aperture rings rapidly back and forth a number of times to get some of the oxidation off the metal surfaces to restore proper resistance values from the potentiometer.

Donald I have a beautiful black FT2 with he same issue. I very seriously doubt it's the photocell since the failure rate of Cds cells is practically nill. I also not think it's a faulty resistor ring (like the Nikon F2 meters). I'm afraid an internal solder joint or something or another is causing a higher resistance in the metering circuit.

wiltw said:

Set ISO 125, 1/125 shutter, and meter a clear blue sky, and the reading should be 'about f/16'...the birghtness of the sunny sky DOES vary from the sunny 16 rule of thumb! If that result is not what you get, the meter is malfunctioning.. The issue might be that the potentiometer (whose value changes with aperture/shutter) could have some oxidation on its surface. You might try changing shutter & aperture rings rapidly back and forth a number of times to get some of the oxidation off the metal surfaces to restore proper resistance values from the potentiometer.

Click to expand...

I'll give this a try when I'm at home.

beemermark said:

Donald I have a beautiful black FT2 with he same issue. I very seriously doubt it's the photocell since the failure rate of Cds cells is practically nill. I also not think it's a faulty resistor ring (like the Nikon F2 meters). I'm afraid an internal solder joint or something or another is causing a higher resistance in the metering circuit.

Click to expand...

I have (some years ago) had the photocells replaced in a Pentax Spotmatic SP -- since there were no replacements available, the repairer was able to use cells from a Pentax 67 (removed from their housings?) and the camera worked fine afterward -- but CdS cells do fail. Not frequently, but... Either way, I'd expect high resistance to go with low light, i.e. an open solder joint would read low at all times. In my case, if I close down the aperture and shutter speed far enough, I can get the needle to center, but it's obvious the exposure is wrong for the set ISO and lighting.

My EL is intermittently underexposing by 2 shots, and I'm not sure what the cause is.

Do what Wiltw said. I think your indoor lighting is too dark and the meter does that to tell you that the light is lower than its measuring range.

Chan Tran said:

Do what Wiltw said. I think your indoor lighting is too dark and the meter does that to tell you that the light is lower than its measuring range.

Click to expand...

I see two problems with that idea. First, shouldn't the meter read "-" instead of "+" in that case? And second, I first noticed the problem in full daylight (though it was after changing from 400 to 50 speed, so it could be the speed setting potentiometer).

Okay, I tried multiple film speed settings and apertures, and compared the reading against the light meter app on my phone (which seems accurate enough for even streetlight photography).

In light where the phone read 8 seconds at f/5.6 EI50, the camera was reading 1/500 with the same aperture and set film speed -- but the needle did center as that setting. I count that as 11 stops high (as in film will underexpose that much), maybe 12, depending what shutter speed progression you think in...

Not certain, but the FT2 could use a circuit that employs behavior like the Wheatstone Bridge circuit, which is not dependent upon a specific Voltage from the battery that powers the circuit. And it is possible that higher-the-expected resistance in one potentiometer could lead to the need for higher resistance values from one (or even more than one of the other pots) to balance, leading to a false reading. Ergo, try to sweep the pots from one extreme to the other rapidly multiple times, to break down any surface oxidation of the metal surfaces of the potentiometer.

wiltw said:

Not certain, but the FT2 could use a circuit that employs behavior like the Wheatstone Bridge circuit, which is not dependent upon a specific Voltage from the battery that powers the circuit. And it is possible that higher-the-expected resistance in one potentiometer could lead to the need for higher resistance values from one (or even more than one of the other pots) to balance, leading to a false reading. Ergo, try to sweep the pots from one extreme to the other rapidly multiple times, to break down any surface oxidation of the metal surfaces of the potentiometer.

Click to expand...

I did that when I was checking at different film speeds; the speed setting and shutter speed share on pot, and the other (for aperture) is based on the position of the rabbit ear linkage. I moved both from one end of travel to the other multiple times, with no change in behavior.

I have been told by folks who ought to know that the FT2 uses a bridge circuit to be non-critical on battery voltage (so can operate correctly on a silver oxide or alkaline vs. mercury cell only). Even if battery voltage were well out of range (a nearly dead battery, for instance, at < 1 V), I wouldn't expect to see it read a dozen stops high. My two FTn bodies are voltage dependent, which (along with needing to stop-down meter) is why the FT2 is my Nikon of choice.