# Understanding EV on a spot meter

ev zone system exposure

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### #1 christopher valkenburg

christopher valkenburg

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Posted 21 November 2012 - 01:16 PM

Hi folks,

Please forgive my noob question but I am learning about exposure. I understand the zone system and how to place areas on zones. I know there are zones 0-9. What I don't understand is, when looking at my spot meter, I have EV, or exposure value, increments. There doesn't seem to be a limit to the number of EV values and I can't understand how EV and zone values correlate or how to use them.

Please could you shed some light on this?

Thanks!
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Posted 21 November 2012 - 03:33 PM

Personally; I don't use EV. I don't see a point to really. I just need to get the F stop number for what I'm looking at given a certain ISO/Fps/Shutter Angle, which I like to define myself instead of have it algorithmically designated. I'd say EV is better for stills where you can/do change the shutter speed often to get an exposure.. but even then, I like doing it on my own so I can control the motion blur ect.

But this is a pretty good explanation of it

http://en.wikipedia..../Exposure_value

Basically; each EV is a stop; or a Zone. So once you figure out where your middle grey is in EV (let's say it's EV 10, then EV5 would be -5 stops, and EV15 woudl be +5)... if that makes sense.. But again, for me, I just stick with F top numbers.
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### #3 Chris Millar

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Posted 21 November 2012 - 08:37 PM

There is no limit to EV values as there is no limit to light (at least for the purposes of this discussion).

They are log2 transformed values referenced to some value I'm not too sure of but I think something to do with a standard 100asa exposures and so on- anyhoo, you are correct in thinking they scale similarly to the zone system does but where you've gone awry is perhaps not recognising that the zone system has a limit on zones due to the very limits of film based media.

Light - which is to say 'un-sensed' light - has no relative limit in that regard.

Sure, your light meter senses the light like film does, but think of it having much more range than your film ever would.
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