Joe wrote:
My new puppy, the FA 77, seems a bit slow in autofocusing. So I did the following test. I took my FA 50 f1.7, FA 31, and FA 77, focused each manually to its nearest focus point, mounted each on the camera in turn, turned the focus ring until the autofocus drive engaged, and autofocused on a tree rather far away (about 100 yards/meters). The FA 50 f1.7 and FA 31 both snapped into focus quickly, and at about the same speed. The FA 77 was perceptibly slower. When I remove the lenses and turn the focus ring by hand, they all seem to have about the same amount of resistance.
So, why should this be?
I've found this too. The 43 and 77 focus noticeably slower compared to the FA50 and FA*85 I have (very unscientific testing I grant you). I've also noticed the Ltds hunt a bit more than the ordinary FA's. It doesn't worry me too much since I really only need the FA*85 in AF mode.
I don't know if you can tell how fast the AF should be just by the (linear) resistance of the MF ring. I would think the moment of inertia of the lens would be more important. Still, I'd be interested in understanding why this should be so, as well.
D
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