Hi,
I have the pleasure to be the owner of said lens since last week and I thought I'd report my early feelings about it and maybe ask a few questions around.
First, it's probably the best lens I have ever owned in it's range, my first tests have sold me on it's IQ withour restrictions.
Construction is excellent and I am really happy to get back the FoV of my old 80-200 f2.8 without the bulk and weight.
AF precision is top notch.
Now, for the discussion.
Having read about it's AF capabilities, I begun by keeping firmware to 1.11 in my K10 and used the lens with screw-drive AF last week.
Two impression son this period:
1/ AF is quite loud.
2/ Compared to my FA 135f2.8, the AF is slower with a little bit of hunting.
I'd say moderately fast AF.
Now I switched to v1.3:
1/ AF is near silent, except for small 'cliqueting' sound when focus is achieved: nice!
2/ Compared to my FA 135f2.8, AF is slower but with less hunting.
I'd still say faster AF this time but the gain is not on the max rotational speed which is still slower than the FA lens.
Also, keep in mind an important fact about the two lenses I am comparing: with the FA 135f2.8, AF throw for going from 1m to infinity is about 80-90°, on the DA*, it's around 100-110°, that's quite a long way to go.
While focusing from infinity to 2m, the FA lens rotates very quickly (much quicker than the SDM), passes beyond the AF point, stops, comes back a bit, eventually adjusts by tiny steps and locks (all that in around a second or so).
For the same job, the SDM rotates slower but stops at the AF point, eventually adjusts by tiny steps (my impression is that it does that much less than the FA) and locks.
Now, the impression when you just make the lens rotate from one end of it's range to the other (with lens cap on) is that the FA lens is super fast while the DA* is pretty slow but when you actually focus on an obect, the total AF time seems about the same but the "AF scenario" is different.
The FA ruches back and forth into focus while the DA glides in.
Of course, differences are only visible when you focus alternatively from close to far, in minor AF adjustments, both lenses are really fast.
To me it looks like the SDM motor is limited by the maximum rotational speed it can communicate to the lens. The in-body motor of the K10 is one of the most powerfull I have seen yet, it really jerks lenses into focus pretty loudly but it's maximum rotational speed is high. The SDM motor is apparently not capable to attain the same speed.
Now comes the question: can AF speed of SDM lenses be improved by a newer body?
When I asked a friend of mine who just switched from the Canon 10D to the 40D what were his feeling regarding AF speed with his 70-200f2.8 USM lens, he replied: "Day and night, the 40D is clearly much faster".
I also wanted to chime in in the 1D series forum on DPR with a question like: "Do you think AF speed of a 70-200f2.8 USM is the same on a 400D than on a 1DMkIII (OK, MkII might be a better idea these times
) but something kept me from doing it (fear of death maybe?
).
So I'm left wondering, with in-camera AF motor, you switch to a camera with a more powerful motor and get instantly faster AF on all your lenses.
But with SDM, is it possible to get faster AF on future bodies or is everything limitated by the motor you implanted in the lens in the first place?