Urgent: sigma 18-50 2,8 ex dc (not macro) vs 17-70 dc macro 2,8-4,5

About these two sigma which is better? I have readden various opinion and very different.

I am also looking at similar lenses one of them being the 17-70, going to try a few asap then will make a purchace

My daughter had a Sigma 18-50 EX f2.8 and it wasn't very sharp at any setting, think its the luck of the draw with Sigma.
Lot of as new condition s/hand ones about, but not overly sure these aren't bad examples that have been returned then offloaded

The 24-70mm f2.8 is nice if you get a good'un, but daresay the same can be said about most lenses
Seems all the Sigma that say "aspherical" on the lens body were the mk1 versions and had problems, the later ones seem better
Think I would only buy new or from someone you trust when they say its ok

Now this is a nice lens, sharp at all settings and a goodly price too, never heard a bad word about them and available in Pentax fit since last year.
link

Cheers
Rich

I have a Sigma 18-50mm DC ex, non-macro. When it first came out it seemed to get good reviews but, and unfortunately not unusual, once a few people had got their hands on it there were some significant complaints about purple fringing. Certainly mine suffers badly from this although it only really appears on subjects with hi-contrast transitions.

I can't comment on the 17-70mm but I think it is a much younger design.

Glyn

Edit - I can't quickly find a review of the Pentax fit version but a review of the Canon fit version can be found here and this highligths the purple fringing issue.