01-13-2011, 12:04 PM
[quote name='wim' timestamp='1294903493' post='5464']
4) For lenses with maximum apertures smaller than F/2.8 (larger f number IOW), AF accuracy according to Canon specs is within 1 f-stop of aperture selected, and therefore the resutl you seem to be getting is within spec (AF is just within DoF), as the 0, which I assume is yoru focusing point, is still within the DoF zone. Note that with lenses with a maximum aperture of F/2.8 and faster, this is 1/3 of DoF, provided you use one of the fast AF points (with most non professional models, which includes even the 5D II, this is the center AF point). Of course, with the 24-105L this doesn't help you, as it will only work with the AF-points for slower lenses (effectively, a fast AF point will become a slow one with a slow lens, they are generally implemented as dual AF-points).
[/quote]
wim: thanks for your input, this helps a lot.
Does 4) mean, that a F/2.8 24-70 L Zoom focuses more accurate and/or faster? (I've a 60D body).
Does the focus capability scale further with the speed of the lens, i.e. does a F/1.4 lens autofocus even more accurate and faster that a F2.8 lens?
4) For lenses with maximum apertures smaller than F/2.8 (larger f number IOW), AF accuracy according to Canon specs is within 1 f-stop of aperture selected, and therefore the resutl you seem to be getting is within spec (AF is just within DoF), as the 0, which I assume is yoru focusing point, is still within the DoF zone. Note that with lenses with a maximum aperture of F/2.8 and faster, this is 1/3 of DoF, provided you use one of the fast AF points (with most non professional models, which includes even the 5D II, this is the center AF point). Of course, with the 24-105L this doesn't help you, as it will only work with the AF-points for slower lenses (effectively, a fast AF point will become a slow one with a slow lens, they are generally implemented as dual AF-points).
[/quote]
wim: thanks for your input, this helps a lot.
Does 4) mean, that a F/2.8 24-70 L Zoom focuses more accurate and/or faster? (I've a 60D body).
Does the focus capability scale further with the speed of the lens, i.e. does a F/1.4 lens autofocus even more accurate and faster that a F2.8 lens?