Sharpness at 35mm

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 35mm

At the centre of the image, sharpness is good when shooting “wide open”, which is beyond the maximum recommended f/3.5 aperture. Unsurprisingly, it is sharper from f/3.5, and is also sharp at f/5.6. Sharpness drops off slightly incrementally up until the narrowest aperture of f/22, but it’s pretty good if you are only viewing images at normal viewing or printing sizes. Edge sharpness is less impressive if you examine images at 100% - it sharpest between f/11 and f/16.

Aperture	Centre Crop	Edge Crop
Wide
f/3.5
f/4
f/5.6
f/8
f/11
f/16
f/22