Metering variations

AJQS

AJQS

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After the issues of Mercury batteries and metering arose with my Konica Autoreflex, I decided I;d do a couple of tests to see what my cameras were doing.

Pointed them all out the window at the same scene. Konica + 40mm wanted f5.6 and 1/30 at ISO 100. Pentax MX and 40mm wanted 1/8! The ME and Super A wanted 1/15 and the GH1 agreed with the Konica and being new fangled digital lark I was able to confirm that was the correct exposure.

So test 2, indoors under a crappy energy saver bulb, hold up Black OM2 against a black background, GH1 says 1/10 @ f5.6, Konica says f4.5 for 1/15 so pretty much the same, MX says the same. At least they agree indoors, but why 2EV range on the outside scene? :thinking:

Time to buy a lightmeter me thinks!
 
Was there a significant difference in tonality in some parts of the outside scene?

That all the Pentaxes agree with each other suggests something to do with their weighting.

BTW, the Konica is an Autoreflex T with TTL metering?
 
Musicman said:
Was there a significant difference in tonality in some parts of the outside scene?

That all the Pentaxes agree with each other suggests something to do with their weighting.

BTW, the Konica is an Autoreflex T with TTL metering?
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Outdoors was 3 parked cars bundled together, most of the scene being a silver BMW, the other 2 being dark green. Centre of the finder was the bonnet of the BMW. I thought this would have been more likely to fool them into underexposing as it's obvioudly brighter than the rest, but the MX saw it as being really really dark!

The Konica is an Autoreflex TC with TTL. :thumbs:
 
Oooohhhh, might this be a polarisation thing? Perhaps the path to the MX meter is slightly polarisation selective. Reflections off a bright bonnet could then be filtered and you'd see an effect on the metering. Easily tested in the same way you check polarisers (or by putting a CPL on the lens to get rid of the linear pol components).
 
AlanSmithee said:
Was your digital set on center weighted metering?
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I have no idea, it has 3 metering modes: (.), ( ), and .

I usually use spot metering on it's own when I'm actually using it seriously, only used (.) for these tests as it's probably closest to Centre weighted, but what it actually is I don't know. Multi spot probably :shrug: Not that it really matters because correct exposure is correct exposure however you get there, it's just interesting seeing how different cameras, even from the same brand, don't reach the same conclusion on the same scene.
 
I looked up the instructions for the GH1 and "(.)" is multiple metering (also known as matrix, pattern or multi metering depending on the brand) which divides the scene into segments and examines their luminosity then combines their luminosities with an algorithm to calculate the exposure also depending on factors such as focus distance, focus point etc.

"( )" is centre weighted metering like that on the MX and Super A so it gives more weighting to centre of the image. Using different metering modes will give different exposures outdoors because of things such as the degree of sky in the picture etc which matrix metering will take into account but not necessarily centre weighted if its not enough towards the centre.
If you were to test it again using centre weighted on the GH1 I suspect they would be within 1/2 a stop of each other.
 
Can you actually get meters calibrated?
 
Alan Clogwyn said:
Can you actually get meters calibrated?
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When I took my Spotmatic F in for a CLA, I asked if he could calibrate the meter since it seemed to be off compared to my K1000 and ME Super like you did. And he said, yes, and asked whether I wanted it calibrated using the original 1.3V or 1.5V battery system for the camera. Testing the meter afterwords against the other cameras again has it reading just about the same.
 
AlanSmithee said:
When I took my Spotmatic F in for a CLA, I asked if he could calibrate the meter since it seemed to be off compared to my K1000 and ME Super like you did. And he said, yes, and asked whether I wanted it calibrated using the original 1.3V or 1.5V battery system for the camera. Testing the meter afterwords against the other cameras again has it reading just about the same.
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In theory with the Spotmatic F it doesn't really matter which battery you use in it as it has a voltage regulating circuit in it so you should get the same meter reading even if you put a higher voltage battery in it.
 
s162216 said:
In theory with the Spotmatic F it doesn't really matter which battery you use in it as it has a voltage regulating circuit in it so you should get the same meter reading even if you put a higher voltage battery in it.
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This is partially true - the circuit used means that a correct exposure will occur with different voltage batteries. However if you try to use the deflection of the needle from the centre position to estimate the amount of over or under exposure then this deflection will change with voltage.
 
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