A620 AV Mode Quirk

When I use my A620 in AV mode it sometimes will not allow me to go below 3.5. I turn the camera off and on again and it allows me to go back down to 2.8. If I up the apeture again and then try to back down to 2.8 it will not let me until I restart the camera. Is there something wrong?

No. The A620 only offers f/2.8 at its shortest focal length (7.3 mm). At 29 mm, it's only an f/4.1 lens. As you zoom the fastest aperture you can use will change. When you turn the camera off, then back on, it reverts to a known focal length (I don't remember what), which allows f/2.8. Then you zoom some more and lose it. But if you were to zoom back to widest settingh, you'd get f/2.8 back.

I'm going to guess when you zoom in, it won't go wider than 3.5, but at startup it's zoomed out and shows 2.8? That's a characteristic of most - if not all -- zoom lenses... less light gets through when going toward the tele end of the range.

(Edit: Ah! Jon beat me to it.)

Thanks, I knew there had to be a reason, I just didn't know.

The effect you've described comes from the lens being a variable aperture zoom - the widest aperture available changes across the zoom range. There are constant aperture zoom lenses that have same maximum aperture across the zoom range - some of Canon's L series EF mount lenses are constant aperture zooms. Constant aperture designs tend to be rather expensive.

David

Not to mention require a much larger front element(s) than would be practicle on a compact camera.