Samyang 16mm F2 ED AS UMC CS

Sharpness

Prime lenses have a distinct advantage in image quality due to optical design over zoom lenses, and that is that they tend to be generally sharper. In our testing of this lens, the center, edge, and corners were tested in both a studio and outdoor setting. The camera used for this testing was a Pentax K-3.

Outdoor test scene

The following are full-size crops of the above scene at various apertures

Center

The center of this lens is remarkably sharp. The sharpness is good from F2.0 through F2.8, and has a sweet spot from F3.5 to F8.0 as seen in the detail of the moss. Starting at F11, there is a fairly linear increase in the amount of image quality degradation due to diffraction. Post-processing tricks such as using a raw editor to do sharpness tuning or using an unsharp mask can help alleviate the loss in sharpness when used wide open.

Edge

Testing the edge of the frame produced similar results to the center of the frame. There is a noticeable sweet spot from F4.0 to F8.0, with larger amounts of diffraction setting in past F10. Past F10, the sharpness becomes noticeably softer, as does the contrast.

Corner

Though there is a decent amount of distortion in the corners of the frame, they are still remarkably sharp. The same pattern of a slightly soft sharpnness wide open until F4.0 leading to a sharp mid-range, with noticeable diffraction towards the smaller apertures continues in the corner of the frame. The same fall off of sharpness and contrast starts around F10

Test Chart - Center

The charts pictured are full size crops taken at a distance of roughly 2 meters.

Sharpness peaks near F4.0, with very little discernable difference at F5.6. This agrees with our field testing in that mid-range apertures are generally the sharpest for this lens. At the wide end, there is noticeable softness, and at the narrower end after F11, diffraction takes over and sharpness begins to fall off and a slight bit of over-exposure becomes apparent.

Test Chart - Edge

Testing the sharpness near the edge of the frame shows a similar sweetspot of around F5.6 observed in real-world testing. The vignetting at large apertures and slight over exposure at F22 both become more pronounced in the edge of the frame.

Test Chart - Corner

The studio corner test agrees with our real world testing. Vignetting is most prevalent in the corners of the frame where exposure was needed to be bumped up a full stop, and sharpness peaks from F4.0 to F8.0 of apertures. 

Full-Size Samples

To judge the Samyang 16mm's sharpness yourself, click on any image below for full-size image samples of our test scene.

F2.0		F2.8
F4.0		F5.6

Verdict

When using a landscape lens, sharpness is important to preserve details, especially around the corners and edge of the frame. The Samyang 16mm does an excellent job producing sharp details throughout the frame when stopped down to F4. It is still acceptably sharp when used wide open, but diffraction sets in and introdoces a noticeable softness at F11 and below.