Quick question on 350d

silly question really, do the peripheral focus points on the 350d go cross sensitive? if so at what f. stop?

And would the focus speed from the stock lense to the sigma 24-70 f2.8 or 50 f1.4 USM contribute to a large increase in focusing speed and accuracy in comparison to the stocko 18-55 lens?

almost all lenses will be faster focusing than the 18-55

not 100% sure on this, but i think the only cross sensitive focus point is your center point. again, don't take my word on that but i'm pretty sure it's the case.

On the XT/350D, only the center AF sensor is a cross-type sensor. The two above and below the center are sensitive to vertical lines. The four to the left and right of the center are sensitive to horizontal lines.

This sensitivity pattern is indicated by the shape of the AF boxes in the viewfinder. An AF sensor is sensitive to lines crossing a long edge of the box. (In other words, a vertical box is sensitive to horizontal lines.)

Doug Pardee wrote in post #4011071
On the XT/350D, only the center AF sensor is a cross-type sensor. The two above and below the center are sensitive to vertical lines. The four to the left and right of the center are sensitive to horizontal lines.

This sensitivity pattern is indicated by the shape of the AF boxes in the viewfinder. An AF sensor is sensitive to lines crossing a long edge of the box. (In other words, a vertical box is sensitive to horizontal lines.)

no, the XT/350d does not have any cross type points. in fact, only the 20d/30d/400d have an upgraded center point, and only the 40d has cross types everywhere (though all but the quirky extra center af point are f5.6 ones, which means they are not as accurate as the 1d mkIII's f2.8 crosstypes). 1d(s) series until the mkiiis have only 7 crosstype points in the center with the rest horizontals.

basroil wrote in post #4011112
no, the XT/350d does not have any cross type points. in fact, only the 20d/30d/400d have an upgraded center point

This is incorrect. The center AF point on the XT/350D is a cross-type. The other cameras offer a high-precision center AF sensor with lenses of f/2.8 or faster which the XT/350D does not, but all Canon DSLR AF systems use a cross-type center AF sensor.

thanks for that, I gues i have to get a new lense and a 40d then