To compare real-life performance
we shot the same scene with each lens within moments of each other using
a Nikon D2X set to Large Fine JPEG mode, optimised for quality rather than
size, and with A for Image Sharpening and Tone Compensation. All lenses
here were set to f8 using Aperture Priority mode. The crops are taken from
the originals and presented here at 100%.
The image left was taken with the Nikon D2X using the Sigma 18-200mm at
35mm f8; the original JPEG measured 5.54MB.
The centre crops in the middle row clearly show the Sigma being the sharpest,
although when it comes to the edges, the Nikkor lens takes the lead. Both
out-perform the Tamron here.