Lens review
Nikon Nikkor AF-S DX 18-200 mm f/3.5-5.6G IF-ED VR
8. Vignetting
Without a doubt, the biggest drawback of the tested lens is vignetting. The situation is really unfortunate at 18 mm. The wide open aperture causes a light fall off in the corners of the frame at 37% (-1.34 the value of the diaphragm). Stopping down the lens does not help. For f/4.0 the vignetting reaches as much as 31%, for f/5.6 it is 21%, for f/8 – 19% and for f/11 it's 16%. One can evidently see that, even with the diaphragm stopped down, the vignetting is high and never reaches an acceptable value of 10%.
The best situation is at 50 mm, which does not mean it is acceptable. With a wide open aperture the light fall off in the corners of the frame reaches 21% (-0.66% the values of the diaphragm). When stopping down to f/5.6 the light fall off is down to 13%, while only when using f/8 can we reach a value of 7%.
When we get to the higher focal lengths, the situation is almost as bad as for the wide angle. For 100 mm and f/5.3 the light fall off in the corners of the frame reaches a value of 31% (-1.07 the value of the diaphragm). For f/8 it is still visible (14%) and it drops to 7% with the f/11.
The situation at 200 mm is very similar. For f/5.6 we notice 32% light fall off in the corners (-1.12 value of the diaphragm). For f/8 it drops to 16% and for f/11 it is 8%.
In conclusion, Nikkor does not deserve any applause in this category. As an example, the Tamron 18-200 had just as weak results at 18 mm, while at the rest of the focal length range the Tamron, with its 10-18% for wide open aperture, had much better results than the Nikkor.
