Testing: Longitudinal Chromatic Aberration and focus shift
Lenses with focal ratios of f2.8 or larger are often prone to longitudinal color aberrations (loCA, a.k.a. “axial color” or “Bokeh CA”). These normally show up as magenta coloration in the foreground and greenish hues in the background and are not easily corrected in post-processing. But the Sony FE 50mm f1.4 ZA is pretty good in this respect: it shows only some loCA wide open. The following 100% crops show the foreground on the left and the background on the right with the first crop at f1.4, second at f2.0, third at f2.8:
The following real life shot shows some magenta haloing around high-contrast edges even in the focal plane and a weak green outline around background subjects:
Sharpness and contrast
Let’s have a look at the theoretical performance of the Sony FE 50mm f1.4 ZA first and compare it to some alternatives:
The MTF charts of the Zeiss-designed Sony ZA lenses shows the contrast wide open at 10 line-pairs per mm (in red), 20 lp/mm (green) and 40 lp/mm (blue). Higher values are better (more contrast) and the closer the solid and the dotted lines are together the less astigmatism (= resolution depends on the orientation of the test-pattern) the lens has. The Sigma Art shows 10 lp/mm (red) and 30 lp/mm (green) at f1.4. The x-axis displays the distance from the optical axis (=center of the sensor) in mm.
From the charts the Sony FE 50mm f1.4 ZA looks very good with a very even performance across the sensor right up into the full-frame corners. In that it looks almost like the Zeiss Otus. Both the Sony FE 55mm f1.8 ZA and the Sigma Art show some roll-off in sharpness from around 10mm image height with the Sony profiting a bit from its less challenging f1.8 aperture. But let’s see how this theoretical performance of the lenses translates into real life results in the sharpness test based on Siemens-stars at 4 mm (center), 13 mm (APS-C-corner), and 20 mm (FF-corner) off axis. Processing was done in Lightroom 8/CRAW 11 from RAW to Adobe Color profile. Noise-reduction is set to 0, sharpening to 50/0.5/36/10, with no extra tone, color, or saturation adjustment. White-balance was adjusted to a neutral white and I did some exposure compensation to make the brightness of all crops match. So you will not see light fall-off in the corners.
The following 100% crops show the Sony FE 50mm f1.4 ZA shot on a 42MP Sony A7R II from f1.4 down to f11.
These 100% crops directly from a 42MP Sony A7R II sensor show very good performance in the center and the full-frame corner. The APS-C-corner is a bit softer wide open but improves nicely when stopped down to f2.8. The lens suffers a bit from field-curvature at this distance so I had to re-focus for each crop to get the best results.
The following comparison shows the Sony FE 50mm f1.4 ZA, Sigma 50mm f1.4 Art, Sony FE 55mm f1.8 ZA, and Zeiss Otus 55mm f1.4 wide open. The Sigma Art and Zeiss Otus were shot on a 46MP Nikon Z7 (mounted via Nikon’s FTZ adapter). Linear resolution of the Nikon Z7 sensor is only 4% higher than from the Sony A7R II sensor which favors the Sony lenses a bit in this comparison but should not make a distinct difference:
In this comparison the Sony 55mm f1.8 ZA and the Zeiss Otus looks best, followed by the Sony FE 50mm f1.4 ZA which is hampered a bit by its soft(er) APS-C-corner, and the Sigma Art with the softest FF-corner (but a very sharp center).
Performance at long distances
The Siemens-star test-targets are shot at a distance of 45x focal length (i.e. at around 2.3m). But as performance of lenses also depends on the shooting distance I did another series of test-shots of a city around 1 km away. Processing was done in Lightroom 8/CRAW 11 from RAW to Adobe Color profile with the lens-profile automatically applied. Noise-reduction is set to 0, sharpening to 50/0.5/36/10, with no extra tone, color, or saturation adjustment. I used autofocus at the largest aperture and did not change focus for other apertures. All shots of the Sony FE 50mm f1.4 ZA were made on a 42MP Sony A7R II at ISO 100 and image stabilization switched off.
The main image shows the complete scene wide open to give you an impression of the angle of view and to judge vignetting. Following the main image are 100% crops from the Sony FE 50mm f1.4 ZA from the center, the APS-C-corner and the FF-corner down to f11. You can access the respective full resolution shots up to f11 via the links beneath the main image or by clicking on the respective crops. Please respect our copyright and only use those images for personal use.
Again the Sony is a bit soft in the APS-C-corner in this long distance test at f1.4 and needs stopping down to f2.8 to produce really crisp high contrast edges. But the lens is very sharp in the center (with just a touch of magenta outlining around high-contrast edges) and in the FF-corner even at f1.4.
The following comparison shows the Sony FE 50mm f1.4 ZA, Sigma 50mm f1.4 Art, Sony FE 55mm f1.8 ZA, and Zeiss Otus 55mm f1.4 wide open. All lenses were shot at the same day within minutes. Only the Sony FE 55mm f1.8 ZA was shot a few days later but under absolutely comparable atmospheric conditions:
In this long distance comparison the Sony FE 50mm f1.4 ZA is the sharpest in the center followed by the Sigma Art, Sony FE 55mm f1.8 ZA and the Zeiss Otus. In the APS-C-corner the Sigma Art is the softest while the others are of comparable acuity. In the FF-corner the Sony FE 55mm f1.8 ZA is amazingly clear with the FE 50mm f1.4 ZA and the Zeiss Otus sharing second place and the Sigma Art being the softest.
To make it easier to see light fall-off in the corners of a full-frame sensor I’ve arranged a series of shots with all three Sony standard prime lenses at different apertures for comparison. All images were developed to the same brightness in the center. Shading Compensation was set to Auto.
The sample images above show that wide open the Sony FE 50mm f1.4 ZA has the worst vignetting. But that was to be expected as the other two standard lenses have a focal ratio of only f1.8. But at f2.0 the FE 50mm f1.4 ZA clearly pulls ahead with very little vignetting.
Rendering of point-light sources at night-shots
Night-shots pose a different challenge for lenses as the contrast is even higher than under bright sun and point-light sources can reveal some weaknesses such as coma, haloing and color-aberrations that do not show up as prominently in other test-shots. The 100% crops below the main image show the effect of coma in the FF-corner of the Sony FE 55mm f1.8 ZA, Sigma Art, Nikon and Sigma Art at various apertures:
The Sony FE 50mm f1.4 ZA is practically free of coma, even at f1.4. Excellent! Both the Sony FE 55mm f1.8 ZA and the Zeiss Otus produces only a little coma wide open. The Sigma Art shows the strongest effect which is hardly reduced when stopped down to f2.0. This is certainly the major cause for the soft full-frame corner of this lens.
Rendering of out-of-focus point-light sources
This test is for the rendering of point-light sources in an out-of-focus background. The circle of confusion that is produced by this test is pretty indicative of Bokeh performance (in the background) and light fall-off. Ideally the out-of-focus image of the point-light is evenly lit and perfectly circular, with no “onion-rings”, and without coloration. Large aperture lenses normally produce an effect known as “cat’s eye” the further away from the optical axis the point-light is projected. This is due to optical vignetting in the lens barrel when light enters the lens from an angle.
In the center the Sony FE 50mm f1.4 ZA produces Bokeh balls that are 20% larger than from the FE 55mm f1.8 ZA but 10% smaller smaller than from the Zeiss Otus. They are very smooth without onion rings but show a bit of outlining which becomes stronger towards the corners. The cat’s-eye effect looks pretty normal, similar to the Zeiss Otus, a little stronger than from the Sigma Art but less pronounced than from the FE 55mm f1.8 ZA. The latter also showing some onion rings and a less smooth structure in the Bokeh balls than the other three lenses.
Let’s see how this analysis of out-of-focus point-light sources translates into Bokeh-performance shooting a book-shelf.
The comparison above shows again why f1.4 lenses are preferred over f1.8 lenses when it comes to Bokeh: The Sony FE 55mm f1.8 ZA has the weakest Bokeh of the bunch especially in the middle-ground. Of the f1.4 lenses the transition zone of the Sony FE 50mm f1.4 looks less soft than from the Sigma Art but a little less busy than from the Zeiss Otus.
50mm focal length may not be the classical choice for portraits on a full-frame camera but the Sony FE 50mm f1.4 ZA can well be used for upper body or full body shots or offers an angle of view equivalent to an 80mm lens on a cropped APS-C sensor. And the background blur at closer shooting distances is nice enough to give it a try. All shots were done from the same position/distance so perspective does not change between shots. But due to the slightly different focal lengths of the lenses and different sensor resolutions of the cameras the images and crops show a little different framing and magnification. There are also some slight focus-differences which inevitably occur when you shoot a living, breathing subject.
Background blur is the nicest from the Zeiss Otus which also produces a very smooth transition in the model’s hair. Second is the Sigma Art followed by both Sony lenses which render the background a bit nervous – the Sony FE 50mm f1.4 ZA looking even a bit more nervous than the FE 55mm f1.8 ZA.
Flare and ghosting
Catching a strong light-source shining directly into the lens is always a risky business: it could produce strange colorful ghost-images or reduce contrast considerably through flare and glare. The appearance of flare and ghosting depends on factors like the aperture and the angle of the light hitting the lens. So to judge the proclivity of the Sony FE 50mm f1.4 ZA for these artifacts I went through a series of well calculated shots against a strong light source to provoke glare and ghosting.
The Sony FE 50mm f1.4 ZA is not very prone to flare and ghosting artifacts. The following image at f11 is one of the most obvious examples:
The little square inset in the upper left of the image shows the respective area with an exposure compensation of +3 EV to make it easier to see which levels of black the lens renders at that point. It clearly shows that the Sony FE 50mm f1.4 ZA renders a very deep black against contra light. Just beware when the light is just outside the corner: it might produce a nasty streak. But this happens only in a very narrow angle:
All-in-all the Sony FE 50mm f1.4 ZA let’s you shoot confidently under adverse contra-light situations.
Next check out my sample images!Check prices on the Sony FE 50mm f1.4 ZA at Amazon, B&H, Adorama or WEX. Alternatively get yourself a copy of my In Camera book or treat me to a coffee! Thanks!