AF Lock and 1 Focussing Point

[wenyao]

Having browsed through the Powershot website yesterday, I found the specifications of the Pro90IS to be having

An AF Lock feature (?!)
and 1 AF Focussing point.

Does anyone know how do I activate AF lock and exactly which is the 1 AF point?

[GaryBerg]

You lock AF by pressing the shutter button half-way down.

[mlfrancis]

The 1AF point means there is one autofocus point, most likely the center of the viewfinder/LCD. The G2 (probably other, but this is the only one I have) can have three different autofocus points: center, left, right. Most SLRs today have 5,7, maybe more autofocus points and they usually pick the point that is covering the closest object to you. More AF points usually make it easier to frame your subject off center.

The G2 has three points, but I find it a useless feature because you have to tell the camera which one you are going to use. There are quicker ways of doing it.

Hope that helps.

[Wildman]

To lock the exposure setting, press the shutter halfway, then press the * button. It'll hold the settings till the shutter is pressed all the way down to take a picture.

[wenyao]

I don't think the Pro90IS has a central focussing point. There are times when it will not lock on the central target in focus at all; according to Botzilla's website, it (and the G1 as well) uses a contrast-based AF system, and not a center AF sensor? can anyone confirm this?