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Samyang / Rokinon AF 85mm f/1.4 FE - Review / Lens Test - Analysis |
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Lens Reviews -
Sony Alpha (Full Format)
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Page 2 of 3
Distortion
The Samyang AF 85mm f/1.4 FE produces a minimal pincushion distortion of ~0.2% in RAW mode. With active image auto-correction, the remaining traces are gone.
Vignetting
Ultra-fast lenses tend to have a very high vignetting at large-aperture settings and this also applies to the Samyang lens. At f/1.4, the 2.2 EV (f-stops) light falloff is very visible in RAW files. The issue is greatly reduced at f/2 and decent from f/2.8 onward.
This is little to worry about with image auto-correction, of course (other than increased corner noise). In this case, the vignetting is already moderate (0.8EV) at a fully-open aperture and a non-issue beyond.
MTF (resolution)
Ultra-large aperture Samyang lenses tend to follow a certain pattern. The resolution is somewhat mediocre at maximum aperture but superb at medium aperture settings. This also applies to the AF 85mm f/1.4 FE. At f/1.4, the center quality is high but lacks biting qualities. The outer image field is fairly unexciting with rather weak corners. The contrast level is also reduced. Stopping down to f/2 boosts the resolution quite a bit already with an excellent broader center and a pretty good outer image field. The peak performance is reached between f/4 and f/5.6. The center quality is great here and the borders/corners are easily very good. As usual, diffraction is a limiting factor at f/8 and f/11 although that's mostly in the center whereas the border quality remains very high. f/16 (not shown) should be avoided if possible.
The field curvature is low. The centering quality of the tested sample was Ok with more noticeable variations at f/1.4.
Below is a simplified summary of the formal findings. The chart shows line widths per picture height (LW/PH) which can be taken as a measure for sharpness.
If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations
Chromatic Aberrations (CAs)
Lateral CAs are on a low level with an average CA pixel width between 0.5-0.6px at the image borders. This is pretty negligible.
Bokeh
If you invest in an f/1.4 lens, you tend to do it for shallow depth-of-field photography and the quality of the bokeh is important - maybe even more so than sheer sharpness. The Samyang / Rokinon AF 85mm f/1.4 FE has some strengths and weaknesses here.
Out-of-focus highlights are nicely rendered in the image center. They are "feathered" thus creamy at the edges and the inner disc is very clean. Unfortunately, traces of a more edgy aperture are already showing up at f/2, and more so at f/2.8.
The circular shape is also only maintained in a fairly narrow zone in the image center (at f/1.4). The shape deteriorates rapidly with rather pronounced "cat eyes" in the corners. Stopping down broadens the "good" zone in the center whereas the corner rendering isn't ideal. The corner highlights are more pleasing at f/2.8 but still not perfect (besides the general edginess).
The quality of the general blur is smooth in the image background (shown to the left below). The foreground is just slightly worse but still pretty good.
Bokeh Fringing / LoCA
Boheh fringing (sometimes referred to as LoCA) is an axial color fringing effect with purplish halos in front of the focus point and greenish beyond. The Samyang AF 85mm f/1.4 FE produces very pronounced fringing at large-aperture settings and still very visible at f/2.8. This isn't surprising for such an affordable lens.
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