Spotmatic F with odd meter issues ...

Thanks for the replies all. I've got it topless (ooer) at home at the moment for a good clean and I'm going to test and adjust the two metering circuits at the same time. I guess I can setup a properly metered scene at EV 8 or 12 or something and adjust the spotmatic from there, both stopdown and open aperture metering.

SOOooo ...

I retrieved my SMC 28mm and, fiddling with the two variable resistors at EV16 and EV8 I've gotten the open aperture metering circuit well inside what I'd regard as acceptable readings compared to my sekonic and checked against my F100 with the same lens fitted via an adapter. Not too much adjustment needed either, which suggests that the two CDS cells (or whatever is in the spotmatic) are ok.
The difficulty is with the stop down metering. Even adjusting the seperate variable resistor for the stop down metering to its extreme I cannot get the stop down metering to read at anything other than about 2 stops underexposed. This has me confused because it's the simpler of the two circuits, and it's reading off the same two CDS cells which appear to be just fine. Anyone suggest any possible avenues of investigation ?

Interesting (by which I mean annoying) side note, you have to put the top back on the spottie to actually get the meter to read correctly. That led to some perplexed fiddling and weird erroneous readings until I worked it out :confused:

Unscrew the lens 1 turn (to uncouple the aperture coupling) and adjust the stopdown metering to be accurate. I'm pretty sure this stopdown metering is only supposed to be accurate with old lenses.

Don't forget to keep the eyepiece covered when metering, the cells can see through there...

If you find that you can get it to work easily along this line of reasoning... Then I suspect that's what the balance control is for.

Bill Burk said:

Unscrew the lens 1 turn (to uncouple the aperture coupling) and adjust the stopdown metering to be accurate. I'm pretty sure this stopdown metering is only supposed to be accurate with old lenses.
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Click to expand...

Sorry, I should have clarified. I was testing the open-aperture metering with a 28mm SMC tak with the proper lugs to engage the aperture tabs on the mount. I was testing the stop down metering with an older 50mm super takumar which doesn't have those lugs (i.e. isn't designed for open aperture metering).

OK so it sounds like a bit of a problem.

To rule out angle of view differences, you could try both with the 28mm - unscrew it (and set the lens switch to Manual) so you use the same lens to do both tests...

For what it's worth, when I tried this Full aperture metering gives two stops overexposure, and Stopdown metering gives one stop overexposure on mine, compared to Sekonic spotmeter...