Can Someone Explain This To Me (5DM3)

[Hesham]

I have been shooting in my backyard (dark), viewfinder blocked. For the same scene, I am getting three different shutter speeds (AV, ISO 1600, 5.6)

(1) Live View: 5 seconds
(2) Live View (OFF), LCD Light (OFF): 2.5 Seconds
(3) Live View (OFF), LCD Light (ON): 2 seconds

Now I understand the impact of LCD light (any news Canon!!), but why am I getting twice the shutter speed (slower) when using the live view?

Note: I have posted the same question in dpreview.com forum!

 

[swampler]

Metering mode different between liveview and viewfinder?

 

[VirtualRain]

I don't know how the camera meters in Live View... Let us know what you hear on DPReview.

Does this happen when using the normal viewfinder method?

 

[Hesham]

Metering mode different between liveview and viewfinder?

When using live view, metering is limited to evaluative, which is what I used without live view (I even tried all other metering options)

 

[swampler]

Are you using a tripod with exact same framing?

 

[Hesham]

Yes!

 

[jrod]

I believe the metering is completely different during live view. My theory is it could be 1 of a couple things

1. It is possible you are getting better isolation from light leaks in Live view since the mirror is locked up, so the viewfinder/meter/LCD is completely blocked from the imaging sensor.

2. My other guess is since the iFCL meter requires the mirror to be down, Live View uses some sort of RGB metering based on the input from the imaging sensor instead, this could cause a discrepancy as well.

Just my two cents