Zeiss Ikon Meter

I always thought it was my job to decide on the exposure, all the meter ever does is measure the light.

If you simply follow it without applying any reason to the reading I'd not be surprised if the results were variable.
 
Moriturii said:
You should download the .pdf from the film you are using (TriX for example), and see how much exposure compensation you should use on that specific film then run your own test and see what you come up with.
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Right, that makes sense. Thanks.

EdwardKaraa said:
Joakim, your ZI meter seems more accurate. Factor 5 is 2 1/4 stops not 3.
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Cool. Do you know the math? I understand that the factor is 2 ^ stops, but can't figure out how to do the reverse equation :D
 
Joakim Målare said:
Cool. Do you know the math? I understand that the factor is 2 ^ stops, but can't figure out how to do the reverse equation :D
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Pretty simple really.

1x, 2x, 4x, 8x, 16x... etc correspond to 0, 1, 2, 3, 4 f/stops.

I don't know the formula but it's easy to interpolate the in between values.
 
EdwardKaraa said:
Pretty simple really.

1x, 2x, 4x, 8x, 16x... etc correspond to 0, 1, 2, 3, 4 f/stops.

I don't know the formula but it's easy to interpolate the in between values.
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That's only valid for linear series. Which is why a factor of five is more like 2.322-something stops (trial and error on the calculator :p). Too bad I forgot most of the math I did in school... All sorts of weird stuff, but what we don't understand is easy to forget.

Who cares really, 2-2.5 stops works for me :D

Thanks Edward.
 
The math is pretty easy:
The number of stops n is the logarithm to the base of two of the filter factor N:
n = log2(N)

Most calculators don't have log to the base of 2, so you can use log to the base of 10 by:
log2(x) = log10(x)/log10(2) = 3.32 * log10(x)

So, a factor of 5 is log2(5) = 2.32 (or 2 1/3) stops.

But if you are in doubt of your meter readings, wouldn't it be smarter (faster) just to do some test exposures instead of doing math and searching for internet links?
 
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