The aim of this test is to compare image sharpness at 200mm at different apertures. I have shot the scene below at ISO 100 with my new 18-200 VR lens @200mm, on a Nikon D80 body. Shots are in natural light (coming from a window to the right) and are taken with a tripod. All shots are JPEG L, normal quality, with no post-processing of any kind.

Shots taken at different apertures are compared at three different magnifications: full frame, 2.4x and 6.4x crops, the latter corresponding to 100% magnification. I also had each crop printed on 13x19cm paper for a visual comparison. On 13x19cm paper, 2.4 x and 6.4 x magnifications roughly correspond to crops from blow-ups at 30x45 cm and 80x120 cm, respectively. Depending on the size of your screen, they will of course correspond to different blow-ups. Still, the idea is that the 2.4x crop correspond to a medium enlargement, and the 6.4x crop to a large one.

Crops are centered on the autofocussed area, on the front bars of the bird's cage. Differences in sharpness due to different depth of field are obvious, try to consider only difference in sharpness in focussed areas. Images are shown as they come out of the camera with standard presets for sharpness, contrast, etc...

I leave the images for you to judge by yourself. If you wish, feel free to drop me an email. Thanks!