Samyang 85 mm f/1.8 ED UMC CS
5. Chromatic and spherical aberration
Chromatic aberration
Although the lens features just one ED glass element it is obvious that it cooperates with the rest of the optical system well enough to ensure appropriate correction of the longitudinal chromatic aberration. Photos, shown below don’t feature anything worrisome. |
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Perhaps these are not perfect results, because we call them so if the lens’s aberration is 0.04% or lower, but still we are among values that can be described as low. On stopping down they get closer to medium ones but, fortunately, they never reach them.
| Fujifilm X-T2, RAW, f/1.8 | Fujifilm X-T2, RAW, f/16.0 |
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Spherical aberration
When it comes to the spherical aberration correction you can express some reservations. First photos of this chapter do show a focus shift. After closing down the aperture from f/1.8 to f/2.4 the depth is noticeably shifted toward longer distances. What’s more, defocused circles of light reached before and after the focus are distinctly different, a quite characteristic feature for not properly corrected spherical aberration. Still we have to add it is not an especially serious problem because the image quality near f/1.8 remains very good and photos you get by that relative aperture aren’t misted, often a characteristic sign of serious problems related to spherical aberration.
| X-T2, f/1.8, in front of | X-T2, f/1.8, behind |
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