Not all lenses are created equally.

From my recent experience in buying nikkor lenses, I realized that not all lenses are made equally. About 4 months ago, I bought the 18-200/3.5-5.6. The shop had 3 of the same lens and so I tried all three shooting on a focus test chart at 45 degree diagonal. All three lenses gave slightly different result. Last week I bought a 105/2.8 macro/micro lens. The shop only had the one lens. After taking it home and comparing it with the 18-200 zoom shooting bank note at the same magnification and aperture, I found that the micro lens is not as sharp as the zoom. (Incidentally I also compared the images with the Canon 100mm macro on 5D Mark II and the 18-200 nikkor is only marginally less sharp). Since prime macro lenses are the sharpest lens, I took the macro lens back to the shop and exchange for another one; the test shots of the new macro are sharper than the zoom as expected (and about the same as the Canon 100mm macro or marginally better at the edge @f8-11). Therefore it pays to evaluate and choose your lenses. I guess small variation in lens sharpness is to be expected at most new lenses are made from many pieces of glass. Would be interested to hear if others have the same experience.

I have the 105 /2.8 and it was the lens of choice until I got used the the tamron 180mm.
However-- the first 180mm that I bought was a disaster--
I sent it back, bought another and the difference was amazing-- without the benefit of your sophisticated testing, I would say that the sharpness is approx. the same in both lenses. I keep wondering what happened to the one I sent back???

Jennifer

I've hear professionals talk about a lens that was exceptional within a group of lensesn.

Makes one wonder what type of quality control testing is done before shipping of lenses?

I wonder if any Nikon, Canon, Tamron, etc. reps monitor this site??? Perhaps they could share.

the fisch

The quality control of the major lens makers is very poor these days. There is a reason why people spend tons of money on Leica

That's a common issue, and unfortunately, it applies to high-grade lenses as much as to lower-end lenses. I've had way too many decentered gold ring Nikkors in my hands to believe that Nikon really tests the stuff well before shipping it. And from some posts on message boards, Canon isn't any better. So, the only thing you can do is testing samples... which honestly is a pain.

I talked with a professional photographer once who addressed this issue. He said that whenver he buys a new lens he orders two of the exact same lenses, tests them both, and returns the weaker of the two. That was the easiest way for him to make sure he got a sharp lens.

I once spoke to a person who shot at the Olympic Games in the trap discipline. He bought two identical Perazzi guns from the factory but found the one shot a superior 'pattern' that could not be explained by any means. It seems there are too many minute details in such sophisticated machines as shotguns and cameras that can make a difference (and cannot be explained).
Of course, you could change to a Pentax system and just buy the Pentax prime lenses. Now that's good glass!