I bought a Canon 50mm f1.4 lens for my Canon 40D. I noticed that the internal light metering doesn't operate in the Av mode. If I use AEB, I can see the metering change for each exposure on the LCD, but not when I change the aperture in the Av mode. I called Canon and was told by tech support that it won't show if I am in Av mode, but only if I am in Manual mode. When I use my other lenses in Av mode, I can see the needle for exposure move on the LCD screen. So is the support tech telling me the truth or not? Thanks. Cindy

id imagine that because you are using a semi automatic setting and only choosing the aperture the camera is instantaneously making its own decisions for the other paremeters. out of interest - are the other lenses canon also?

One lens is the Canon 70-200mm f4 and another is the lousy Canon 28-135mm. The others are Sigma 17-70mm, Sigma 70-300mm and Tamron 90mm.

is this the problem?

also found this:

'In Av mode the camera will determine an exposure based upon a reading from its internal reflected light meter and, by default, is set to no exposure compensation (the indicator will read 0 and, as you point out, does not move around if you change the aperture - it adjusts to give you what it thinks is the correct exposure). To adjust this, which you'll need to do for many of your shots since the camera's meter is so easily fooled, you use the Quick Control Dial on the back of the camera, and you'll see the indicator can be moved within a range of +/- 2 stops.'

It may be, Phil. I have to leave for work, but I'll check this out again tonight when I have time to read it through. Thanks so much. Cindy