I love my Tammy 28-75, it's usually on my camera 90% of the time. Plus, if you are doing portrait photography I wouldn't recommend getting anything wider than 50mm since you risk distorting your subject's face. The 28-75 is pretty versatile though, which is why I love it. I always feel like my 16-45 is a little short when I'm trying to capture a close-up of my little one's expression at times and the extra reach from 50-75 helps. For the money you can't beat it though.
If you have the funds I'd look at the Pentax 50-135 too. I've seen some great portrait shots from that one also and with equestrian photography I'm starting to need a little bit extra reach that is faster than my 70-300.
I actually just ordered the 50-135, and I'm pretty excited. I'm considering the Tamron 28-75 because I was on a shoot last week with my FA 50 1.4, and there were many times I thought to my self "If I could just zoom in/out just a bit, it would be nice." Plus, it is a bit smaller that the 50-135. I just think it is a lens that I would have on my camera A LOT.
An excellent choice - particularly if you're not going to have the 50-135 with you all the time.
If you do think of bringing the 50-135 with you when you're out with your camera, then consider if you'll ever want to go wider than 28mm. This would make the Tamron 17-50, Sigma 18-50/2.8 or the Pentax 16-50 better choices (depending on how much you want to spend).
Sigma and Pentax also have a 17-70 lens, the Sigma does not have a constant maximum aperture across its focal range, but the Pentax version is a constant f/4.
There's also Pentax's 16-45, which is an excellent lens at quite a cheap price, but of course no SDM or weather sealing.
Another option is the only slightly wider Sigma 24-70/2.8, but you lose an extra 5mm at the long end compared with the 28-75...
overall it is an excellent lens, but I have noticed occasionally it can be a little soft, wide open.
If you are considering this lens, you should also consider sigma 24-60 and 24-70 lenses although both are bigger and heavier.
The 28mm leaves it a little on the long side, especially when paired with a sigma 10-20. you notice the 8,mm gap, (i fill that with my SMC FA-J 18-35)
if you are only shooting digital, you might also want to look at something like a 17-70. I shoot both film and digital (except with the sigma 10-20) and full frame was a coinsideration for me.
70 can be cropped to 75. 28 cannot be cropped to 24...
28 is wide enough for me 70% of the time though, so I'm not complaining And I got a great copy luckily n first try.
True enough -- I like to have a wider option for a walkaround lens, but for portraits, 28-75 on a digital is pretty ideal. I seem to usually need just a hair longer than 50mm to get a comfortable distance from my subject and sometimes come in to the 35-40mm range. Strictly speaking for portrait use, having the 28-75 instead of a 17-50 and a 50-135 would mean probably not having to change lenses during a session.
Depends on the type of portraiture.
Single or couple portraits would be easily managed with the 50-135, and I couldn't think of a better lens to do the job.
Any larger groups would need a wide-normal zoom... so the 28-75 might do reasonably well there, but I've had instances where in tight spots even 18mm is not wide enough for a group shot!