Strange issue with 7D

I was photographing a waterfall today and my fist couple shots turned out way too dark. The next couple were right on without changing anything. I was shooting in AV mode but nothing else was changed including the lighting. They were shot 1 after the other from a tripod. After looking at the exif, I noticed my shutter speed was over 2 stops difference in the pics. I ended up shooting in manual mode. And of course, now that I get home I can't duplicate the issue. Anybody else ever had a similar issue?

What metering mode were you using? If can drastically change settings based on how much of the image it's metering.

gjl711 wrote in post #19419119
What metering mode were you using? If can drastically change settings based on how much of the image it's metering.

Particularly when shooting anything where the white/black levels swing drastically. With waterfalls, this normally happens when a large "puff" of water occurs during heavy flows that causes a 'hotspot' in the image, or when clouds/trees move and change the brightness around the area being metered. In sports it happens when different colored jerseys are moving through the frame; as another example. With highly dynamic subjects, you either need to *really* pay attention to what the light is doing and be ready to dial in some EC; or do as you did, and switch to manual.

gjl711 wrote in post #19419119
What metering mode were you using? If can drastically change settings based on how much of the image it's metering.

It was set for center weighted and the camera was on a tripod and never moved nor did the field of view. I just pressed the shutter a couple times with just a few seconds between actuations.

Snydremark wrote in post #19419140
Particularly when shooting anything where the white/black levels swing drastically. With waterfalls, this normally happens when a large "puff" of water occurs during heavy flows that causes a 'hotspot' in the image, or when clouds/trees move and change the brightness around the area being metered. In sports it happens when different colored jerseys are moving through the frame; as another example. With highly dynamic subjects, you either need to *really* pay attention to what the light is doing and be ready to dial in some EC; or do as you did, and switch to manual.

This actually makes some sense. Thank you!

mn shutterbug wrote in post #19419142
This actually makes some sense. Thank you!

Certainly Spot and Center-weighted Avg would be the two modes to show the most drastic results there, so that does track. The good news is that there's a very low likelihood that something went/is wrong with the camera!

You didn't have exposure bracketing turned on by accident did you?