Originally posted by VaughnA One stop is the difference. Aperture only isn't an indicator of a quality lens, there are a lot more factors than just the max aperture. In fact, the older 10-20 F4-5.6 seems to get better reviews than the newer F3.5 constant aperture version. And for the Ultra-Wides something around 3.5-4 is pretty much the norm in the moderate price ranges. I LOVE the 10-20 F4-5.6 that I have, it's my favorite lens.
Ditto, or pretty close. I like my older 10-20 as well, very much.
Quote: And also remember that with a super-wide you can go much slower on the shutter speed than on a longer lens.
Not sure I'd put it that way. I'd be okay if you'd said, "With a longer focal length you will need a much faster shutter to minimize the effects of camera shake." But it just SOUNDS wrong to me to suggest that wider focal lengths allow shorter shutter speeds. It's just just about camera shake: there's also subject motion. Shake reduction has less of an effect—that is, it's less important—with wide lenses. But if you are shooting sports with the 10-20, well, you may need a 1/500th sec shutter. And if you are shooting some part of a landscape (or the moon) with a 300mm lens, you may be able to put it on a tripod and take a 1 second exposure.
Anyway, we agree that the Sigma 10-20 with variable aperture is a great lens!
Will