Hi all,

Canon 6D, Canon 24-105mm F4

I have a bit of a weird question. On the weekend my fiance and I went to some old settler's village here in Sydney, Australia to shoot some photos. I usually use my camera on auto ISO when using TV or AV mode. I was shooting an old abandoned house with a stormy sky behind it. It wasn't dark that day, just overcast a bit. The weird thing is when I went to focus on the house I was on F4.0 as I was using my 24-105mm. When I focused on the house it went to 100 ISO and 1/4000 shutter speed. Needless to say the photos looked very, very dark. I tried a few shots and the same thing happened. I went changed the ISO to 800 and the shutter speed still went to 1/4000. I turned around to take a photo of the orchards under the same sky and the camera functioned perfectly on auto ISO, but back again towards the house and it went out of whack again.

I was able to get some good shots when I switched to manual and made all the settings myself (4.0, 125ms, ISO 800) but in auto ISO and even with the camera on 800 ISO it still went to some incredibly fast shutter speed and made the whole photo look pitch black.

I also turned off auto lighting optimiser but still no luck.

Any ideas what could cause this? I'm happy to shoot in manual for this kind of thing if I can but I was hoping to be able to use AV mode especially if I'm in a hurry (ie with a fiance getting bored pretty quickly.