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i;m no lab specialist and don;t normally put so much creedance to MTF charts but in the case of spending so much on a lens, i give them a look. the MTF's are not as good as the 18-50mm sigma or the tammie i think. plus its much, much heavier and bigger.

so i guess my question is why is everyone so favourable about this lens ? it seems overpriced and not such a strong performer considering the sigma 18-50 f2.8 seems to be sharper and produce very comparable quality for a third of the price.

i'd really like someone to advise why they would buy the nikkor at that price. is it just the build quality, speed and silent focussing difference ?

thank you.

Rooz wrote:i'd really like someone to advise why they would buy the nikkor at that price. is it just the build quality, speed and silent focussing difference ?

thank you.

You've just said the point here. The build quality of a Nikkor is far superior to any other third party lenses. In fact, they *might* sustain far more beating and extended use for those who require them on a daily heavy duty basis.

Quality wise, I've seen very good samples from the Sigma and Tamron lenses (27-70, and 28-75 respectively) and they are very good match to the Nikkor 17-55 or 28-70.

The big difference in optical quality comes in when the lens is wide open, from what I've seen the Nikkor is sharper wide open at f2.8 than the other third party lenses. While they can be shot at f2.8 but the quality in sharpness falls greatly at that, and there is where your price comes to justification again.

In summary, you get what you paid for, quality, long lasting built, and the superior performance at wide open aperture. If these are not your priority, or at least you don't really care much about them, then the third party lenses will do just fine at a fraction of the Nikkor price.

Yi-P wrote:The big difference in optical quality comes in when the lens is wide open, from what I've seen the Nikkor is sharper wide open at f2.8 than the other third party lenses. While they can be shot at f2.8 but the quality in sharpness falls greatly at that, and there is where your price comes to justification again..

thanks for the answer. thats a good point you make. wide open the nikkor is indeed sharper. stopped down the sigma for example is equal - superior.

i guess i just expected alot more from the lens considering its $2000 price tag. as an example, the 70-200VR is off the charts sharp compared to the 3rd party opposition plus it has VR so it makes sense and you can justify investing in its excellent optics. the 17-55 imo just doesn;t excel enough to justify its price tag...not to mention it has no VR. gotta say i'm quite dissapointed in the nikon offering in this area considering at least canon offer the IS "walkaround" f2.8 version.

Mechanical qualities aside, there is much more to optical performance than just resolution (that's what MTF charts show). You have to look at geometric distortion, uneven illumination (or vignetting), propensity for flaring and ghosting, colour reproduction etc.

Cheers
Steffen.

Rooz wrote: the sigma 18-50 f2.8 seems to be sharper

funny but true.

as someone pointed out sharpness isn;t everything and i totally agree, especially wide open which was a really important point. but centre sharpness of both the tam and the sig stopped down are better than the nikkor.