-3 EV, what is that?

I consider myself to be reasonably competent at interpreting specs, but one spec I've never really understood is autofocus and EV. The spec of the 6D is as follows:

•11 point AF system, center point cross-type and sensitive to -3 EV

So here's my question. My 5D3 focuses just fine when I move exposure compensation to minus 2.5 stops. It also works just fine in near darkness (it's good like that!). So what on earth does "sensitive to -3 EV" mean?

Thanks

I'm pretty sure -3 EV is better than the D600 and D800 (-1 EV and -2 EV, respectively) so I'm curious as well.

At -3 EV the 6D is theoretically able to focus in one stop less light than the 5DIII at -2 EV. Exposure compensation has nothing to do with this.

http://www.the-digital-picture.com …-Autofocus-Explained.aspx

"Overall sensitivity is how well the AF system performs in low light. The AF sensor is composed of multiple 48-bit line sensors and associated amplifier circuitry - the more amplification (within the limits of signal to noise), the less light needed to focus. AF sensitivity is specified as an EV range, and the lower the first number, the better. For example, the T3i/600D through 5DII can AF down to -0.5 EV, the 1D IV/1DsIII down to -1 EV, and the new 1D X down to -2 EV. EV units are 'stops' so the 1D X can achieve AF in half as much light as the previous 1-series bodies. "

Oooh cross type 11 point AF. Now we're talking.

From another source:
"Exposure Value zero (EV 0) corresponds to exposure time of 1 second and aperture of f/1.0 . EV 1 is either 1/2 seconds and f/1.0 or 1 second and f/1.4 , etc. "

That is at ISO 100.

So, if my math is correct, this new camera can AF in light where you'd be shooting f/1.4, ISO 100, 16 seconds.

Aressem wrote in post #15004253
Oooh cross type 11 point AF. Now we're talking.

You misread. It is not 11 cross type, it is 11 points with a center cross-type. Not much different than a 5D or 5DII.

krb wrote in post #15004291
From another source:
"Exposure Value zero (EV 0) corresponds to exposure time of 1 second and aperture of f/1.0 . EV 1 is either 1/2 seconds and f/1.0 or 1 second and f/1.4 , etc. "

That is at ISO 100.

So, if my math is correct, this new camera can AF in light where you'd be shooting f/1.4, ISO 100, 16 seconds.

Note that the target isn't described though. You may find the AF wii refuse to lock in light as strong as EV 13 if you attempt to focus on a blank wall. I think the Canon minimum light levels for focus are on ideal targets, probably a pattern of black and white lines.

Aressem wrote in post #15004253
Oooh cross type 11 point AF. Now we're talking.

What? The 6D has 11 points with ONLY the center point being cross-type.

About like the 20D, except this -3 EV low light capability.

I am a "focus and recompose" guy, so this new -3EV might mean much more to me than 61 AF points. Let's see what it translates to in real world shooting...

996gt2 wrote in post #15004326
What? The 6D has 11 points with ONLY the center point being cross-type.

Oh

Considering the Nikon has an AF-assist lamp, does it matter?

krb wrote in post #15004299
You misread. It is not 11 cross type, it is 11 points with a center cross-type. Not much different than a 5D or 5DII.

The 5DII has 6 invisible focus points in servo mode, no mention of this on the 6D, so is the 5DII focus system more advanced? Never thought I would be saying that !

cmosman wrote in post #15004538
The 5DII has 6 invisible focus points in servo mode, no mention of this on the 6D, so is the 5DII focus system more advanced? Never thought I would be saying that !

5D II has more AF points (in AI Servo) but less low light sensitivity (-3.0 EV vs. -0.5 EV).