Metering giving different results in LV and non-LV

I was shooting quick flower macro close ups in aperture priority mode, using a 600D on a tripod. I used liveview zoom to focus. Evaluative metering mode. Natural light.

When I triggered the shutter from liveview, the shot was 'correctly' exposed. When I switched back to viewfinder (i.e. not in liveview), with no changes to any settings, the shot was underexposed by 2-3 stops.

Now, I'm used to evaluative metering sometimes throwing up exposures that are 'incorrect' for what I am trying to shoot, and then adjust EC accordingly (or go to manual).

However, I don't recall ever getting such different exposures (using the same metering mode) when using liveview or viewfinder.

Does anyone have an explanation for what was going on?

Were you looking through the eyepiece or did you have it blocked in any manner when you took the 'non live view' shot? Light entering the eyepiece can throw off your exposure.

Like Jim says, that thing "parked" on you strap is to cover the viewfinder. That of course assumes you read the manual and mounted the device on the strap.

Jim_T wrote in post #15801394
Light entering the eyepiece can throw off your exposure.

Yep........

Jim_T wrote in post #15801394
Were you looking through the eyepiece or did you have it blocked in any manner when you took the 'non live view' shot? Light entering the eyepiece can throw off your exposure.

No, the eyepiece was not covered, though I don't normally cover the eyepiece when the camera is on a tripod, and have never seen this issue before.

Could it make 2-3 stops difference? Presumably, the amount of light entering the eyepiece would have to be comparable to the light coming through the lens to have such a marked effect on metering . . .?

For reference, I was in dappled shade on an overcast day. I was shooting at f2.8 when this particular issue arose. When I stopped down to f16 (which should increase the ratio of light coming through the eyepiece to that coming through the lens . . . ?), there was no similar problem.

dodgyexposure wrote in post #15801538
Could it make 2-3 stops difference?

I doubt it. Check the exposure settings in the metadata to confirm no other settings changed.

Depends on where the sun was shining. If the sun was shining from behind the camera then the eyepiece would pickup a bit more light then the front of the lens. Also I believe the lightpath from the eyepiece into the sensor is a little straighter with less loss.

The other thing as well though is the metering normally vs using live view is different. I believe live view uses more of a spot or weighted metering with where your focus point is as the main metering point while the normal mode if used in evaluative mode will try to meter the whole scene.

Metering differs somewhat between normal evaluative and live view metering. That's because evaluative metering emphasizes the area where the active focus point(s) are. Normal focusing allows only AF points in certain places, but can have more than one finding focus. Live AF has more freedom in placement of the AF area, but can have only one.

Light entering the eyepiece can easily throw off the metering by 2-3 stops. The metering sensor is located just inside the eyepiece, so it's very close to the opening and thus easily affected by light coming the wrong way.

I didn't think it would affect the LV metering since the mirror is locked up.

I agree with the post about using zoom on the LCD.
This is from my 60D manual, it might be worth looking at the 600D manual and see if it states the same.
"If you take the picture during magnified view, the exposure might not come out as desired. Return to the normal view before taking the picture.
During the magnified view, the shutter speed and aperture will be displayed in red. Even if you take the picture during magnified view, the image will be captured in the normal view"

Definitely nothing to do with the mirror or the VF not being covered.

CircuitR wrote in post #15802549
I didn't think it would affect the LV metering since the mirror is locked up.

dave_bass5 wrote in post #15802559
Definitely nothing to do with the mirror or the VF not being covered.

The OP says that the LV exposure was correct. Underexposure occurred when he took a similar shot using the viewfinder. This is in line with light entering the uncovered viewfinder, although two to three stops seems quite excessive.

JohnB57 wrote in post #15802593
The OP says that the LV exposure was correct. Underexposure occurred when he took a similar shot using the viewfinder. This is in line with light entering the uncovered viewfinder, although two to three stops seems quite excessive.

Yes but if the exposure was set in LV while it was zoomed in then that could account for the fact that the settings were actually not correct for the VF shot, as he didn't change any setting to take the VF shot.
I read it that the exposure was set while using LV zoomed in.
Maybe i got that wrong then.
The OP has also stated he doesnt normally cover the eye piece and has not had this issue before.

You misunderstood the user's manual. The exposure is never set when the image is zoomed in. It's set before you zoom in, so if you change something, or the light change, then that pre-set exposure may not be correct at the time of shutter release. Go back to full view before pressing the trigger button.

Just because you didn't have problems with light entering the viewfinder before doesn't mean you can't have it now.

I must admit i cant replicate this issue so hopefully it might just be a one off, maybe the lighting did change at the moment the shot was taken.

I am confused as to the light entering the VF though. I always thought when the mirror is locked up (both Live view and movie mode) there was no need to cover the VF.

Yes, but the point here is that the problem occured during normal shooting, not when using live view. Live view gave the correct exposure, normal shooting did not. So you're right, but perhaps you misunderstood the question in this particular case.

To see the issue, use the camera in a dark surrounding, whilst pointing a flashlight into the viewfinder. This is extreme, but will show you the principle.