Originally posted by unixrevolution I appreciate your suggestions very much and you are certainly right about portraits at 100. I do already own a fast 50 for portrait work on the Digital...A Pentax-A 50mm F/1.4.
I know I want a 1:1 macro because I've played with a friend's 100mm F/2.8 macro and loved it. I think I'm going to settle on the Tamron for the following reasons:
1. It has an aperture ring (Unlike Sigma 70/Pentax D-FA 100mm
2. It's only slightly heavier than the D-FA 100mm Macro.
3. It's short length of 90mm Vs. 105 means that it's APS-C equivalent is 135mm, which is the furthest I'd think you'd want to shoot portraits at. So for a good long portrait lens and midrange telephoto, that's the ticket. 90mm is also closer to a proper portrait lens if I use it on my film cameras, which by the required presence of an aperture ring, I'm sure you can guess I plan to.
Did you get it yet? I'm having some funky experiences with mine trying to learn it.
Like Rio said, for macro, forget AF. Not only doesn't the lens know what point you want to focus on (even when you're set for single point), but the damn thing hunts like crazy, even with the limiter switch set.
In addition, for maximum depth of field, you have to back focus anyway. My macro work is to shoot detail, nothing artsy fartsy, so my Tamron isn't going to see anything wider than F22, and it'll probably be at 32 most of the time. (I just started playing with it this past weekend with a flash ring.) But when you get in at the minimum focusing distance and focus on the surface of the object, the DOF is so thin that you have to focus behind that point to get it all clear--and I still wasn't too happy with the results.
As far as spontaneous off-the-cuff portraits go where it's not a set-up shot, although 90 may not seem the ideal length, I really love it because it's long enough to put you far enough away to put the subject totally at use. There's a huge difference in how people react to a camera when it's 6 feet away from them as opposed to 12.
But if I was just using it for set-up Macro work at home, I would probably go with an older, inexpensive, manual prime. The extra cost doesn't warrant it. But in the field doing macro, plus the portrait capacity, it's a well respected lens for the money.