Quote Originally Posted by Cozen
My only concern with the tamron is the auto focus. Anyone have experience with this? Is it really that loud? is it fast and accurate?

This is a mixed bag depending on who's reviews you listen to. I've used the Tamron 17-50 f2.8 DII quitea lot and subjectively I can't say I've noticed anything odd. The only objective points I can stateare:


1) I tested two copies at a local shop and found the first to be sub-par in the IQ department. I own the second which is spot on.


2) Very sharp from 17 to 40 wide open fading a bit toward the long end. I don't use this lens very much at f2.8. f4.0 is optimum.


3) I've never noticed any AF noise and still have no clue what reviewers are talking about. Maybe I just don't pay attention.


4) I've never noticed any hunting in low light unless I was as low as 1600 ISO f4.0 1/30th or slower. Then again my 70-200 f2.8 USM will hunt in that level of light. I'm still wondering why folks blame the glass but that's just me.


It is a screw focus mechanism which means that accuracy will depend on the resolution of the screw mechanism. USM will most of the time have a higher keeper rate whencontending with shallow dof shots. I can't say that I've ever come home froma shoot and been disatisfied with this len's AF performance. I would say that I have about the same keeper rate as the 28-70 f2.8L on my 5D as I do with the Tammy on my 40D.


Personally, I like the the EF 50 1.4 on the 40D as a portrait/candid lens and on the 5D as a scene lens. I am still looking for a good deal on a 85 1.8 for my 5D.


It sounds like you have choosen wisely.


Hope my observation helps.