SQUIRL033 Loc: Chehalis, WA

evidently it's something with the lens itself. i have it on pretty good authority that the lens "fools" the body into thinking it's af f/5.6 even when it's actually at f/6.3, so it's not related to Canon's AF aperture threshold limit. enough people have apparently experienced it, though, and some have reported it back to Tamron, either via dealers or via Tamron field reps, so hopefully it will be resolved soon. it's not a problem for those who shoot only static subjects, but there are enough people out there (myself included) who take it as a challenge to capture birds in flight, and those are the sorts of people who will buy this lens; it would behoove Tamron to address this without delay...

Regis Loc: Coeur d' Alene, Idaho

I appreciate your information. Thank you.
The weather has been bad here so I haven't tried any birds in flight yet except for a distant shot and it looked good but it was to small to see any detail.

SQUIRL033 Loc: Chehalis, WA

BIF shots are a tough test for a lens/AF system. the AF has to lock on and maintain focus lock as the bird moves, the stabilization has to work properly, and the lens has to let in enough light to allow a fast (i.e. 1/500 or faster, depending on the bird and focal length) shutter speed. personally, i try to keep shutter speed at or above 1/1000 for any BIF shot, but in low light, with a relatively slow lens, this can be a real challenge. the jury's still out on how this new Tammy will actually perform. i'm hoping it turns out to be as good for this kind of work as it appears to be for static subjects... if it does, it could really set Canon back on their heels a bit with respect to the value/price equation...

Regis Loc: Coeur d' Alene, Idaho

Thank you. Only time will tell how this new lens will perform over the months ahead.