Time to be with your loved ones

Time to be with loved ones

by sat

submit your photo


Hall of Fame
View past winners from this year

Please participate in Meta
and help us grow.

Take the 2-minute tour ×
Photography Stack Exchange is a question and answer site for professional, enthusiast and amateur photographers. It's 100% free, no registration required.

This question already has an answer here:

I know that it stands for Exposure Value, so my 6D focuses in 2.5EV worse light than a 600D.

But it's relative to... what?

What makes it meaningful? What's the "base unit" for AF sensitivity?

share|improve this question
add comment

marked as duplicate by Michael Clark, mattdm, Itai, MikeW, John Cavan Jan 3 at 4:18

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

1 Answer

up vote 5 down vote accepted

Exposure Value is actually an absolute scale, where EV 0 corresponds to an nominally-exposed photo having an exposure time of 1 second at aperture f/1.0 (or of course equivalents, like 2 seconds at f/1.4).

You can see by that baseline that -3EV is pretty amazing — it corresponds to a minute-long exposure at f/2.8.

We're used to seeing EV in the context of EV compensation, where the camera is told to expose differently from what its meter tells it to, and that's expressed in relative terms (plus or minus some number EV), but the basic scale is actually fixed. More on this a What is the EV scale? and What is exposure compensation?

share|improve this answer
    
I'm reading this to mean that the camera has a "standard exposure value" by which it calculates normal exposure. And, that the two cameras can autofocus in situations with less light by 0.5 and 3 EV (respectively) to that nominal exposure. –  David M Jan 1 at 22:01
1  
@David That is true, and the nominal exposure is as I said: one second at f/1.0 (ISO 100) –  mattdm Jan 1 at 22:17
    
Got it, now! Thanks! Good post! One more question, I would assume that every camera has a different ability to autofocus at even the nominal especially determined by lens type. Can this range be used to quantify the camera's abilities within it's nominal range, or is it merely a function of sensor sensitivity. (Not sure if that question made sense . . .) –  David M Jan 1 at 22:19
    
Thanks. I did notice that the 6D is brilliant to focus even in rubbish indoor lighting. Coupled with a bounce flash delivers excellent results in worst conditions! –  Marcin B Jan 2 at 14:38
add comment

Not the answer you're looking for? Browse other questions tagged or ask your own question.