can this substitute well?

[Kofman13]

im looking at the Nikkor 28-70 2.8 and think its a god lens, all around amazing lens. but im no where near being able to drop $1,300 for a lens.
Is the sigma 28-70 2.8 EX a formidable substitution? its discontinued... but i see it online going for $230

 

[JasonLambert]

I can't speek for your Nikon stuff but a lesson I have learned is that you get what you pay for.

 

[Gaerek]

I don't know about that lens in particular, but in general, the third party lenses (Sigma, Tamron, Tokina) are going to be less expensive than their main brand counterparts. Like Jason said, you get what you paid for, but that doesn't mean it's a bad lens. I would just research, and see what others say about it. That's a pretty darn fast lens for a really good price, and at that price it might just be worth it. But then again, it might be crap. Keep in mind that the third parties do make some amazing lenses. They also make some real turds too. But, Canon and Nikon do the same. Sometimes they hit a home run with a lens, other times, they fail. It's all about the research.