A Day At Alta With The Sony Alpha A55

[Ken Nielsen]

unless I'm trying to focus on plain snow. For that, I think Canon and Nikon would do better.

I don't think so. I have the Canon 7D which has one of the most advanced AF systems out there, but there are certain situations that defy AF, plain sky, reflective surfaces, shooting through glass windows, plain undefined surfaces (like snow,) among others. If you can find even one tree, or a shadow, anything that offers contrast and at the distance that you want to shoot, then you can do a pre-focus on that and then switch to manual to hold the focus is one way of holding a focus setting for another subject at the same distance. AF is pretty neat and very accurate in most situations. On the Canon, a half-press of the shutter button activates AF, but you can choose to change that to a separate back-button on the camera to activate AF, then you can preserve the focus when shooting without the AF being activated again.