ive been looking at different 70-300's for my nikon,i've noticed that the nikon one is like 600,but ive found some others that are way less,whats the difference?? is sigma any good? thanks

 

image quality, focus speed, some might have image stabilization, some might be faster glass and let more light in.

 

The $600 lens has "VR" vibration reduction. It is a must for you are shooting from your hand with out a tripod. That is a very good deal for a 300mm lens. I will be picking up on very shortly.

 

I disagree, the effects of "VR" or "IS" (Nikon and Canon respectively) are nominal. Focus more on image quality and speed, if it happens to come with "VR" or "IS", great - you will probably turn it off most of the time anyway. It's a gimmick.

my .02

 

Sigma 70-300 DG HSM MACRO Autofocus Lens NIKON (Works with The D40-D40X-D60)
Tamron 70-300mm LD 1:2 Macro Lens For Nikon Mount
Nikon 70-300mm f/4.5-5.6G ED-IF AF-S VR NIKKOR Lens

other than the VR on the nikon,how do these compair to eachother

 

The optics of the Nikon 70-300VR are far superior to the non-VR Nikon 70-300 and the Sigma 70-300. If you can get the VR, do it for the superior optics. If not, get the standard Nikon.