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Viltrox AF 75mm f/1.2 PRO XF - Review / Test Report - Analysis |
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Lens Reviews -
Fujifilm X
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Page 2 of 3
Distortion
The Viltrox AF 75mm f/1.2 PRO XF doesn't require any auto-correction when it comes to image distortions. The lens is fully corrected as you can see below.
Vignetting
Ultra-high-speed lenses tend to produce quite a bit of vignetting at large apertures and this also applies to the Viltrox lens. In RAW images, the vignetting is very high (for an APS-C format lens) at f/1.2. A light falloff of ~1.8EV (f-stops) is a bit beyond our usual scale here. Stopping down to f/1.6 reduces the issue substantially and it's not a major issue anymore from f/2 onward. Activated auto-correction reduces the vignetting down to 1EV (f-stop) at f/1.2 already and the issue is barely visible from f/1.6 in this case.
MTF (resolution) at 26 megapixels
Traditionally, such fast lenses struggle a bit when it comes to producing great results at very large aperture settings. However, the Viltrox AF 75mm f/1.2 PRO XF delivers a surprisingly high performance at f/1.2 already. The broader center quality is already very good to excellent here and the border quality is on a good level. The broader center becomes bitingly sharp at f/1.6. It's safe to state that the center quality surpasses the resolution capabilities of the 26mp sensor at f/2. The outer image field improves only marginally when stopping down with a "late" peak at f/5.6 where it reaches very good results. Diffraction has a dampening impact from f/5.6 and becomes more noticeable from f/8.
The field curvature is low. The centering quality of our sample was decent.
Please note that the MTF results are not directly comparable across the different systems!
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 of 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 basically non-existent and nothing to worry about.
Bokeh
High resolution is one thing but if you invest in a fast medium tele lens, you tend to be interested in shallow depth-of-field photography and the quality of the bokeh should be another decision point in this case so let's see what the Viltrox lens can do for you.
Out-of-focus highlights are nicely rendered with a smooth inner disc and basically no outlining at the edges.
At f/1.2, the circular shape of the highlight discs is only maintained in a fairly narrow zone around the center. The highlight shape deteriorates rapidly with pronounced "cat eyes" near the borders/corners. As usual, stopping down broadens the zone of truly circular discs with a broadly corrected zone at f/2. Imperfect corner highlights are still present at f/2.8 though.
The general blur is very smooth in the background - illustrated to the left below. The less important foreground blur is somewhat less pleasing with a more distinctive blur "edge".
Bokeh Fringing / LoCA
Boheh fringing/LoCA is an axial color fringing effect with purplish halos in front of the focus point and greenish beyond.
The Viltrox lens does a pretty good job in this respect. There are only traces of color fringing present at f/1.2 and they are gone by f/2 already.
If you scroll through the aperture range, you may notice that the (fixed) focus point moves to the rear. This is a residual spherical aberration (RSA aka focus shift).
However, the "Zero" mark remains quite sharp so it's not an overly critical issue.
Sun Stars (Experimental)
Below is s sequence of images from f/4 all the way up to f/16 - illustrating the Sunstar behavior (using an LED on a dark background). Sunstars are an aperture effect when shooting bright light sources such as street lights, the sun, etc. The Viltrox lens produces more pronounced sun stars from about f/8 with the best results at f/16. The rays are "pointy" which is quite pleasing.
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