Sharpness at 50mm

For this review, the sharpness test is carried out by photographing a real-world sample, rather than a test chart. The Neptune Convertible Art Lens System was mounted on a Nikon D4S, which was in-turn mounted on a sturdy tripod. Exposure delay was activated to prevent camera-shake. Any changes in tone you might see across the crops are due to natural light changes during the shooting session.

The full frame at 50mm

With the 50mm lens attached, sharpness is pretty good when shooting wide open, but sharper from its “recommended” maximum aperture of f/2.8 onwards. It continues to be quite sharp up until f/11, dropping off a little at f/16 and f/22, but again more than acceptable when viewing at normal printing or web sizes. At the edges, sharpness is more impressive than at the 35mm focal length, with a good degree of sharpness throughout the aperture range. The sharpest results are found between f/2.8 and f/11.

Aperture	Centre Crop	Edge Crop
f/2.8
f/4
f/5.6
f/8
f/11
f/16
f/22