Samyang 85mm f/1.4 Aspherical (full format) - Review / Test Report - Analysis
Lens Reviews -
Canon EOS (Full Format)
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The Samyang produces only a marginal degree of barrel distortion (~0.4%) which is negligible in field conditions.
Note: the chart above has a real-world size of about 120x80cm.
Ultra-large aperture lenses tend to have some vignetting problems on full format cameras. The Samyang shows an edge deterioration of 1.8EV at f/1.4 - this is hefty in absolute terms but relative to similar lenses this is actually quite well controlled. The problem is still visible at f/2 but it's basically gone from f/2.8 onwards. All-in-all a good characteristic based on the current state of the art.
(revised) The lens showed a decent performance on our MTF torture grounds. As expected we measured the weakest performance at very large aperture settings. The center quality is "only" very good (just) at f/1.4 and the borders and extreme corners are a bit soft here. However, this is still fine enough for portraits where the center performance is most important naturally. The contrast level is slightly reduced at this setting. Stopping down to f/2 produces only a marginal increase in quality but there's a stronger boost at f/2.8. The technical sweet spot of the lens is reached around f/5.6 with an excellent (just) center quality and very good borders/corners. Diffraction effects show a stronger impact from f/11 onwards.
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
Lateral Chromatic Aberrations (CAs)
It may be a bit baffling but the Samyang has no real issues with respect to lateral chromatic aberrations. An average CA width of around 0.6px at the borders is not really field relevant anymore.
The bokeh (the quality of the out-of-focus blur) is a primary aspect for an ultra large aperture lens and the Samyang does a good job here. In fact the quality of out-of-focus highlights is pretty much perfect - at least at f/1.4 and f/2. There's only a tendency of producing ellipsoid shaped highlights in the corners but no "cat's eyes". The lens has no circular aperture blades and the more angled projection gets somewhat more visible from f/2.8 onwards. The quality of the general blur is very good as well. You may spot the purple halo on the very last image - that's "bokeh fringing" (see the next chapter).
Bokeh Fringing / Longitudinal Chromatic Aberrations (LoCA)
Bokeh fringing is a common problem in this lens class and the Samyang suffers as well here - like the vast majority of lenses it is no "APO" design. If you look at the provided sample crops below you should be able to spot a purple halo in front of the focus zone and a green one beyond. This is clearly visible at f/1.4 till f/2.8. The problem starts to fade from f/4 onwards.
You may also spot a slight focus shift towards the background when stopping down ("residual spherical aberrations").
Move the mouse cursor over the f-stop marks below to observe the respective LoCAs