Good zoom on a budget? Tamron 28-75 or sigma 24-70?

I'm on a budget but looking for a good quality 'normal' zoom camera lens.

The Tamron 28-75mm and Sigma 24-70 both appeal because they have a good range and both offer constant f2.8. Ignoring the advantage of the extra 4mm of the sigma, how do they compare optically? Anyone used both and care to say which they prefered?

Also, I love the wide angle of my 18-55mm kit lens, and was wondering if I should get the 18-50mm sigma 2.8 instead. How does this compare optically to the above?

Any other similar lenses in this price range (preferably f2.8 and a zoom lens rather than a prime)?

Thanks a lot for your help,

Francis

Had both: preferred the Sigma but would be happy with eather. BTW, these lenses are discussed practically every day here. Do a search and you'll find all the opinions you could ever need.

Well, I can't say I've used both like CondyK, but I have the Tamron, and it is tack sharp and I'm really pleased with it.

I have to agree here and i bought mine used.

Our fellow POTN'er fStopJojo has done some test between the two. Check it out.
http://www.pbase.com/f​stopjojo/24702875

Wow! I just saw fStopJojo's comparison between the Sigam and the Canon 24-70mm - the Sigma performs admirably in all areas, beating it in some sharpness stakes! Extremely impressive given its under half the price of the Canon here in the UK!

Take your kit lens and set it at 28mm for one day, 24mm for one day, and 18mm for a day (in that order too). If you find that 28mm is wide enough (it isn't for me) on a crop body as a walk around, then get the Tammy. If 24mm is a good balance and it's enough, then the 2470EX. If you find you really like walking around with a 18mm zoom, then the Siggie 1850EX. I ended up with the 1785IS, even though it is slightly inferior optically to the above 3, it is hard to beat overall considering all its perks. If you want the highest quality lenses overall, then look at the Canon 24-70L or the new 24-105L IS.

Thanks for the replies.

Hmmm.. I can't help but think that I will miss the wide angle with the Tamron and Sigma 20ish to 70ish varaities. But they appeal for there longer end and f2.8. I guess I discounted the Canon because at the wide end, its slower than my kit lens! But its range does seem perfect - the widest of the 4 going to the longest of the 4. So fStop, is the 17-85mm the lens that is on your camera most of the time?

By the way, your lens tests have been extremely helpful - and they are a great resource.

Depends. With the little tykes inside the home, it's the Siggie 30f1.4. But outside (or recently at Disneyland for example; yes we have an annual pass), it's more and more the 1785IS + 70300IS. I really like the 1785IS because as a walk around lens for me, it's ideal. If I need speed, I grab a prime.

I'm really tempted by the Canon, but here in the UK, its pretty dull and grey most days, (unlike sunny California!), so I'm still worried it won't be fast enough. Though I suppose the IS helps with that...

I can't comment on the sigma but own the Tamron 28-75 2.8 and am very pleased with the results I'm getting. Here are couple of shots I took with it. It seems to be at its optimum at around f8 f11 http://www.photography​-on-the.net/forum/showthre​ad.php?t=126745

I also had that dilemma - having seen fstopJojos tests, I went for the Sigma EX 18-50 f/2.8. For shots where the reach isn't enough, I now have a Canon 85mm f/1.8 which is the mutt's nuts! You would have to spend a lot of money to get a comparably good wide angle lens as the 18-50 EX - the Canon 17-40L is the next best, but it's got a smaller range, and is a lot more expensive (though compatible with full frame bodies).

I think the Sigma EX 18-50 is one of the most underrated lenses. The Tamron and the Sigma 24-70 are both fine lenses, but I love the range of the 18-50, and wouldn't give it up, unless I got a full frame (which aint gonna happen, because I don't want one, and can't afford one).

After looking through the test shots and some other review information, it looks like these two are very similar optically. The Sigma appears to have an advantage in build quality while the Tamron has an advantage in weight.