High ISO images are sometimes overexposed ... why?

[Rupert49]

Taking a few pictures inside my newly refurbished lounge recently, I was using bounce flash (580EXII) with my EOS 5D MkII set to P and ISO 200, as I usually do when using flash indoors. I then decided to try some shots without the flash and turned the ISO up to 6400, changing the camera setting to aperture priority.

To my surprise many of the resulting shots were quite overexposed - something which I can rectify in ACR, but I don't know why this should have been .. unless I'd inadvertently dialled in some exposure compensation, something which is all too easy to do with EOS DSLRs, although I've had several and am usually wise to this!

Thoughts anyone?

[spinno]

6400 is 5 stops more than 200, depends on the lenses used and also was there a nice window...other than thatcan't think of anything.Oh only shutter speed...were you outside the range?

[Rupert49]

I think I may have stumbled upon the answer!

I've just had a look at the exif data for the images in question and I appear to have had the metering set to Spot (rather than Pattern). Looking back through my recent pictures I see that I first used this setting for a few shots of a fledgling robin - a recent visitor to our back garden - on 18th August. All my shots since then have remained on Spot metering, but fortunately they've none of them been vital in any way (weddings or the like).

Might this have resulted in overexposure of a general scene lit by daylight and artificial light?

[LargeFormat]

Might this have resulted in overexposure of a general scene lit by daylight and artificial light?

Might be the answer, depends what you spot metered on. Oxford Dictionary (dark blue) = over-exposure, white paintwork = under-exposure.