Honeywell Spotmatic update.

Mike Kennedy · Feb 14, 2008

I had installed an Energizer 392 watch battery (1.55 V) to power up the meter yet things seemed off.Could be the extra voltage or the cameras age.Who knows ?Just did a test against my Nikon FM2 and found the Spotmatic was 2 stops overexposing.Adjusted the iso and all's well.
Oh yea,the watch battery cost $2.98.A wein cell was $13.50 at my local shop.

Nick Zentena · Feb 14, 2008

Voltage shouldn't be an issue.

The Spots have a voltage circuit that deals with almost anything you could throw at it.

How did you test? Against a grey card?

Mike Kennedy · Feb 14, 2008

Hi Nick,
I didn't think it would be an issue either.Used a grey card under consistant LED light and double checked against a Gossen Pilot lightmeter that I know is tack sharp.
I can't figure out this anomaly.

Mike

Nick Zentena · Feb 14, 2008

LED? Wonder if the meter doesn't like the wavelength?

Sun light would be better.

Mike Kennedy · Feb 14, 2008

Thanks Nick.I'll have a go with sunlight..................when and if it ever reappears in New Brunswick.She's been pretty stormy.

Nick Zentena · Feb 14, 2008

I used to do testing against an inside wall. It had a large window that cast light on the wall. The wall was a zone VI -) If you're having snowing white storms then this might work. If you're having dark cloudy storms then it'll be too dark. But in general cloudy days were great since the light wouldn't change.

cao · Feb 14, 2008

Nick Zentena said:
Voltage shouldn't be an issue.

The Spots have a voltage circuit that deals with almost anything you could throw at it.

Wrong! The Spotmatic F used a balanced bridge with a centered galvanometer. It was indeed supply voltage independent. The earlier cameras had an asymmetric circuit and centered the meter at a specific non-zero current, and the reading would depend on the battery voltage.

Mike Kennedy · Feb 15, 2008

That would certainly explain the overexposure Cao.

Thanks Much.

Steve Roberts · Feb 15, 2008

cao said:
Wrong! The Spotmatic F used a balanced bridge with a centered galvanometer. It was indeed supply voltage independent. The earlier cameras had an asymmetric circuit and centered the meter at a specific non-zero current, and the reading would depend on the battery voltage.

What he said!
There are all kinds of fixes for this on the web, but the one I like the look of most is the alkaline or silver oxide cell with a couple of Schottky diodes in series with the battery to drop the voltage. I have the diodes but have yet to try the scheme. So little time.....
Steve

Mike Kennedy · Feb 15, 2008

I've adopted the motto "Less is Best" when it comes to camera repair.
Last night I was able to test my recalibrated Spotmatic at a friends studio using her lights and high end Minolta meter.Tack sharp (+/-) 1/2 stop with adjusted iso. Now with a 392 Energizer battery I set the asa at 100 with 400 film,32 for 100
Works for me.

Honeywell Spotmatic update.

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