Nikon F3 meter four stops off

[zabin29]

I have a Nikon F3 that is consistently four stops off (underexposed) in manual mode compared to the correct exposure in Aperture priority. Batteries are fresh, aperture index ring moves freely, springs back nicely, and is in the correct position. I did recently mount a non-ai lens on it once on accident without flipping up the tab, and the lens mounted fairly easily (which is why I didn't notice) but was a little more difficult to dismount. Doesn't seem to have caused any damage. Could this be the problem? I do think I remember the meter being OK afterwards, but the timing is pretty close. Any ideas?

 

[Tom1956]

Sounds like dead meter cell(s) to me. Try wiping the battery faces and contacts. Also do not take for granted that batterys are fresh just because they might be newly purchased. Take my tips with a grain of salt, because low voltage typically leads to over exposure, not under.

 

[Chan Tran]

I have a Nikon F3 that is consistently four stops off (underexposed) in manual mode compared to the correct exposure in Aperture priority. Batteries are fresh, aperture index ring moves freely, springs back nicely, and is in the correct position. I did recently mount a non-ai lens on it once on accident without flipping up the tab, and the lens mounted fairly easily (which is why I didn't notice) but was a little more difficult to dismount. Doesn't seem to have caused any damage. Could this be the problem? I do think I remember the meter being OK afterwards, but the timing is pretty close. Any ideas?

Please explain the problem a little clearer? You said it underexposed in manual mode you mean that the meter is off by 4 stop? And you said compared to correct exposure in aperture priority you mean that in aperture priority mode the exposure is correct? Please explain a little clearer.

 

[zabin29]

for example, indoors f/4, iso 400, in manual mode the +- shows up at 1/250 and in Aperture mode it will read 1/15. And the meter will track changes as the aperture and shutter are adjusted, but a 3-4 stop difference remains. And yes, aperture priority is giving almost the correct exposure compared to my digital camera, which is giving 1/25. So aperture mode seems to be overexposing by about 2/3 of a stop. I'll add that I do remember this happening a little while ago, before the non-ai lens incident, and it mysteriously fixed itself within a day. And this current issue just happened today, so maybe I'll wakeup tomorrow and it will be fixed. And I just checked with the motor drive attached, and same issue - so I think that rules out a battery issue.

 

[Chan Tran]

I think it just need calibration. I think all the adjustments can be made via potentiometers under neath the leatherette on the left side of the camera. There are something like 10 adjustments and must be done in correct order.

 

[zabin29]

thanks for your reply, guess I'll bring it in and see what my local tech says.

 

[Christiaan Phleger]

Sounds like a classic case of a cracked FRE unit. Check the left side by the film rewind knob, if any impact damage there the ceramic and gold FRE unit gets a crack and the meter goes off by 3-5 stops, its not Rare but it happens. I had one of my 4 F3's take a tumble on to concrete and thats what got replaced by NPS. The FRE replacements might be in very short supply.

 

[Chan Tran]

If the FRE cracked the same effect for A mode and M mode. The OP said it's OK with A mode. Camera must be put on a calibrated light source / shutter tester to verify the problem. If there is no problem with A mode that is the shutter speed indication in viewfinder and the actual shutter speed are correct and only the shutter speed indication in M mode is off then it's only a calibration of the + - display level. If other problems are found then the problem can be different.

 

[John_Nikon_F]

Plus, if the FRE is damaged, wouldn't you also have twitchiness in the "+-" indications?

-J

 

[zabin29]

There is no impact damage that I can see, the camera is in beautiful cosmetic condition, with barely a mark on it. No twitchiness in the +-. Did a couple test shots in very low light and the meter gave 2 seconds at f/2.8 in A mode and 1/30 in manual mode - that's 6 stops, so maybe the 3-4 stops isn't as consistent as I thought. Both shutter times sounded accurate. Now checking with the lights on, f/5.6 in A mode gives 1/15 and M mode gives 1/1000. Six stops again. So the differential between readings has increased over the past couple days. Just put in a fresh set of batteries (again) and same readings.

 

[Chan Tran]

Check out the operation in A mode and make sure it's working correctly. I know you don't have instrument but you can check and see if it gives correct exposure with film. If the shutter speed indicated in the viewfinder agrees with the actual shutter speed.
Next make sure in manual mode, the speed indicated in the viewfinder is the same as the speed set on the dial. Also the actual shutter speed is the same.
If those checked out you need to adjust 1 potentiometer to correct the problem.
If the camera behaves like I said above then the photocell is OK, the FRE is OK, the shutter speed control circuit is OK.
In manual mode voltage comes from the photocell is subtracted by the voltage generating by the FRE (which is aperture and ISO settings). This voltage is then compared to the voltage generated by shutter speed dial to provide the +/- indicator. The voltage generated by the shutter speed dial also feed the shutter speed display and the shutter speed control circuit.
The 2 possible things is first the adjustment went out of adjustment or the comparator amplifier for the +/- is bad.

 

[zabin29]

Chan, shutter speed in the viewfinder agrees with the actual shutter speed in both M and A modes. And the viewfinder readout tracks the shutter speed dial in M. So according to the two possible scenarios, are these easy adjustments to make and would the comparator amplifier need to be replaced? thanks for your help, i hope this is a relatively easy fix.

 

[RalphLambrecht]

how does it compare to 'sunny 16',which in my opinion works extremely well;at least in the trusty Florida sun.

 

[zabin29]

I've checked the meter in A mode against a digital camera and it's within 1/2 stop, so it's pretty good in that mode. But my M mode thinks the rule is sunny f/130! It's a low key effect.

 

[zabin29]

folks, my f3 meter is working again! great, but I have know idea why. it's been working for the past week.