Which lense to go with my 50d & Sigma 10-20 combo?

I have recently got a 50d as an upgrade to my old 400d. currently, I have two lenses: canon 50mm 1.8 and sigma 10-20, and I would like to add another lens to my collection.

I'm a bit on a tight budget (700$), and I'm torn between three lenses:

1) Sigma 18-50 2.8
2) Sigma 24-70 mm f/2.8 EX DG HSM
3) Canon 15-85

Which one offer better sharpness and image quality?

kookie_sn wrote in post #9784880
I have recently got a 50d as an upgrade to my old 400d. currently, I have two lenses: canon 50mm 1.8 and sigma 10-20, and I would like to add another lens to my collection.

I'm a bit on a tight budget (700$), and I'm torn between three lenses:

1) Sigma 18-50 2.8
2) Sigma 24-70 mm f/2.8 EX DG HSM
3) Canon 15-85

Which one offer better sharpness and image quality?

Tamron 17-50mm f/2.8 VC is a great option at that price. Its often talked about highly on this forum. I personally own the non-VC version and I love it.

Tamron 17-50 non-VC? Do you have a flash? I would say a flash is a good idea if you don't have one.

I don't think you want something that overlaps with your 10-20 sigma...
I am in the same dilemma and was thinking of going for Sigma 24-70 HSM but heard about lots of problems with focusing and after many review I am set on Canon 24-105 since its nice for walk around, good for portraits and have enough zoom for me so I won't switch lenses too much.

Siggy 24-70 is probably best bet.

I have a 40d and the sig 10-20 and will be buying Canons 15-85 as I don't care for my 28-135. I did the searches and asked the Q's and now am convinced the 15-85 will be a perfect fit after I unload my 28-135! Anyone in the market for a clean 28-135?

Tamron 28-75 f/2.8 --- outstanding walkaround lens that complements a superwide quite nicely. For years my walkaround combo was a Tokina 12-24 plus the Tamron 28-75. You're probably not going to miss the 21-27 range if you have 20 and 28.

Sigma 24-70/2.8 HSM or save some money for Canon 24-105