QUOTE(timothyy @ May 10 2008, 08:02 AM)
The major difference is the brand. Nikkor lenses are made solely for Nikon cameras. So, they are so called optimised for Nikon Cam.
As for third party, they are made to suit to every camera...
But... in terms of performance, usually you see many prefer the Nikkor lens compared to third party. Even in terms of performance. But the major issue is the build quality.
I'd say, have the extra bit of money and don't want to regret? Get Nikkor lenses.
Budget tight but still want to buy the lens? Get third party. But make sure do a lot of reading before buying it.
Not really le...
Last time I let my Tamron SP90 vs Canon 100 macro (non-USM version) vs Nikon 105 macro. Surprising at f2.8, Tamron beat both Canon & Nikon at border sharpness!!!
My friends that tend me thier Canon and Nikon version were shocked looking at the results also...
But anyway, the slow and keep hunting autofocusing from Tamron might shorten your life...

And the Tamron 17-50 f2.8 perform surprisely nice on Nikon le....