7D Auto ISO

Dan7312

Any idea how the Canon 7D chooses a particular ISO in auto mode? For example with Av it seems to put the shutter time at about around 1/80 or thereabouts and then ramp up the ISO as needed.

I'm assuming it sets the shutter time there for hand held on a non-IS lens. I don't have an IS lens to try it with, but will it go for a longer shutter time and lower ISO on an IS lens?

Anyone see any doc's about how the ISO is choosen for A other than what's in the instruction manual?

Tnx

ziggy53

The Canon implemenation of "Auto ISO" is one of the simpler varieties and, unfortunately, has little serious application.

The Pentax and Nikon implementations allow much better control and limits.

According to the Canon 7D User manual, page 63, when the 7D mode is set at Auto, CA, P, Tv, Av or M mode, the ISO will float between values 100 and 3200, depending on the exposure. I believe that Highlight Tone Priority changes the available values to ISO 200-3200 (but I don't know this for sure.)

It also appears that exposure compensation is affected, but I'm not sure just how it is affected in the 7D.

I also believe that the shutter speed in Av mode is selected using the closest available shutter speed according to the reciprocal of the focal length.