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 show up as magenta coloration in the foreground and greenish hues in the background and are not easily corrected in post-processing. The Sony FE 24mm f1.4 GM is no exception: it shows pretty strong loCA wide open even down to f2.8. 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:
See an example of this effect in a real-life shot:
The test also revealed that there is a very slight focus shift towards the camera when stopping down but that should be taken care of by the autofocus using the actual aperture.
The Zeiss 25mm f2.0 Batis has a little less aggressive greens (see here, crops are f2.0, f2.8, f4) like the Sigma 24mm f1.4 Art (here) while the Zeiss 28mm f1.4 Otus is somewhere in between (see here).
Sharpness and contrast
Let’s have a look at the theoretical performance of the Sony FE 24mm f1.4 GM first and compare it to the alternatives from Sigma and Zeiss:
The computed MTF charts from Sony and Sigma show contrast at 10 line-pairs per mm and 30 lp/mm at f1.4 without influence of diffraction. Higher values are better (more contrast) and the closer the line-pairs are together the less astigmatism (= resolution depends on the orientation of the test-pattern) the lens has. The MTF chart of the Zeiss lenses shows the measured contrast wide open at 10, 20 and 40 lp/mm. This includes the influence of diffraction . The x-axis displays the distance from the optical axis (=center of the sensor) in mm. I’ll show you the real-life performance at 4 mm (center), 13 mm (APS-C-corner), and 20 mm (FF-corner) on a 42MP Sony A7R II body.
From the charts the Sony FE 24mm f1.4 GM looks clearly better than the Sigma Art. It shows a soft roll-off in resolution towards the corners of the frame with very little astigmatism. Both Zeiss lenses show almost flat MTF charts that speak of very little loss of detail in the corners of a full frame sensor. If you compare the Batis and the Otus keep in mind that the Batis is shows here at f2.0 and the Otus at f1.4. But let’s see how this theoretical performance of the Sony translates into real life results in the sharpness test based on Siemens-stars. Processing was done in Lightroom 8/CRAW 11 from RAW to Adobe Color profile with the built-in lens profile applied. 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. Removal of lateral color aberrations is ON, longitudinal CA are not corrected.
The following 100% crops show the Sony FE 24mm f1.4 GM from f1.4 down to f11 compared to Sigma 24mm f1.4 Art and the Zeiss 28mm f1.4 Otus at f1.4 plus the Zeiss 25mm f2.0 Batis at f2.0. The Zeiss Otus / Sigma Art were shot on a 45MP Nikon Z7 / 36MP Nikon D810 respectively with no lens profiles applied. The linear resolution of the Z7 sensor is only 4% higher than from the Sony A7R II and of the D810 sensor 7% lower which should not make a visible difference in this comparison.
In this comparison at f1.4 the Sony FE 24mm f1.4 GM shows very good performance only shortly behind the Zeiss Otus and clearly better than the Sigma Art. The Sony also had no field-curvature, all crops were taken from the same shot without the need to re-focus.
Let’s do the same comparison at f2.0 now including the Zeiss Batis:
The Zeiss Batis is is a little less sharp in the center but is better in the APS-C and FF corner. The Sigma Art continues to suffer from soft corners and the Zeiss Otus combines both a very sharp center and very good corners.
Now let’s see how the Sony FE 24mm f1.4 GM develops when stopped down further:
Stopping Sony’s FE 24mm f1.4 GM further down helps the lens only slightly as it is already very good at f2.8. Only the FF-corner does not sharpen up completely even at f8 or f11. Btw. with JPGs straight out of the camera the FF-corner looks a bit better probably due to more aggressive sharpening in camera:
You can also see in the above example that Adobe’s RAW converter does not apply the distortion compensation that comes with the lens profile.
Performance at long distances
The Siemens-star test-targets are shot at a distance of 45x focal length (i.e. at around 1m). But performance of lenses also depends on the shooting distance. Therefore I present 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 – as far as Adobe’s RAW converter recognizes it (see above). 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 were made 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. You can access the respective shots up to f11 via the links beneath the main image. Following the main image are 100% crops from the Sony FE 24mm f1.4 GM down to f11 compared to the Sigma 24mm f1.4 Art and Zeiss 28mm f1.4 Otus at f1.4 plus the Zeiss 25mm f2.0 Batis at f2.0. The Sony and the Zeiss Batis were shot on the same day only minutes apart while the Zeiss Otus / Sigma Art were shot another day on a 46MP Nikon Z7 resp. Nikon D810. The small differences in linear resolution compared to the Sony A7R II should not make a visible difference but atmospheric conditions certainly do.
You can click on each image to access the large original. Please respect our copyright and only use those images for personal use.
Again the Sony FE 24mm f1.4 GM and the Zeiss Otus look very similar with very high center sharpness and only little softening towards the corners. The Sigma is the softest in the FF-corner with coma smearing high contrast edges.
Let’s repeat the comparison at f2.0 now including the Zeiss Batis:
The Sony GM has a clear lead over the Zeiss Batis in the center and is a little sharper in the APS-C-corner too. In the FF-corner both lenses look very similar. The Sigma Art is also very sharp in the center at f2.0 but is clearly lagging behind the other lenses in the corners.
Following is how the Sony FE 24mm f1.4 GM develops when stopped down:
Again a very good performance from the Sony 24mm f1.4 GM in this long distance test. The lens can be confidently used wide open and achieve very sharp results across the full-frame sensor.
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 the Sony FE 24mm f1.4 GM, the Zeiss 25mm f2.0 Batis, and the Sigma 24mm f1.4 Art at different apertures. All images were developed to the same brightness in the center and the integrated lens profile applied to the Sony and the Zeiss lens, Shading Compensation in camera was set to Auto. The Sigma was shot on a Nikon D810 with no lens profiles applied in post-processing.
The sample images above show that even with the lens profiles applied vignetting of the Sony 24mm f1.4 GM and the Zeiss Batis are very visible wide open. With no lens profiles applied the Sigma Art looks much worse at f1.4 but very similar to the Sony GM at f2.8. If you apply the Adobe supplied lens profile to the Sigma Art vignetting is almost completely eliminated. But then you can add some additional correction to the Sony GM and Zeiss Batis too.
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 24mm f1.4 GM, Zeiss Batis, Sigma Art and Zeiss Otus at various apertures:
The Sony FE 24mm f1.4 GM produces almost no coma wide open – an outstanding feat! It is indeed the best f1.4 lens I’ve tested so far, better even than the Zeiss Otus. The Sigma Art is clearly the worst of the trio with the Zeiss Batis similar to the Zeiss Otus. The only deficiency I can find with the Sony GM is that it shows some magenta haloing around bright lights at f1.4:
The effect is pretty much gone by f2.0.
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.
A few things are of note here:
- The Bokeh balls of the Sony GM are very smooth inside with almost no onion rings comparable to the Zeiss Otus with the Sigma Art trailing slightly behind. The Zeiss Batis produces very ugly onion rings.
- The Sony GM lens also shows very little outlining in the center, better than the rest. But you can see some green coloration from longitudinal CA which the Zeiss Otus lacks and the Sigma Art has only little. The worst again in this respect is the Zeiss Batis.
- Compression of the Bokeh balls is relatively low towards the corners for the Sony GM and the Zeiss Otus with the Sigma Art showing the worst compression.
- The size of the Bokeh balls in the center crop of a lens is directly proportional to the entrance pupil which makes the Sony FE 24mm f1.4 GM comparable to the Sigma Art and slightly smaller than from the Zeiss Otus which profits from its 17% longer focal length. Likewise the Zeiss Batis cannot compete here with its f2.0 focal ratio leading inevitably to a 1/3 smaller Bokeh ball.
- When stopped down the Sony retains a perfectly circular Bokeh ball with the Sigma coming in second the Zeiss Otus third and the Zeiss Batis last.
Let’s see how this analysis of out-of-focus point-light sources translates into Bokeh-performance shooting a book-shelf.
The Sony FE 24mm f1.4 GM has a very creamy Bokeh in the background and produces a soft albeit slightly greenish transition in the middle-ground. The less important foreground is a bit nervous. The Zeiss Otus is close in Bokeh performance with a softer foreground, less coloration but a slightly more nervous background. The Sigma Art also has a soft middle-ground transition similar to the Sony GM and a bit softer than the Zeiss Otus but suffers from a very nervous background rendering in this image probably due to the compression of its Bokeh balls towards the border/corner. The Zeiss Batis produces the least blurred Bokeh although in the background crop it looks better than the overly nervous Sigma Art.
All-in-all the Sony FE 24mm f1-4 GM produces the best background Bokeh in this comparison with the Zeiss Otus a close second.
The Sony FE 24mm f1.4 GM goes down to 1:5.4 magnification which is similar to the Zeiss Batis, Sigma Art, or Zeiss Otus. Its performance in close-up shooting is pretty good once you stop down f2.8 or f4.0. The following image was shot at 1:5.5 magnification where the area of sharp focus is just 132 x 198mm. The crops shown below are from the center, 10mm, and 19mm off the center of the sensor respectively:
Flare, ghosting, and sun-stars
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 24mm f1.4 GM 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 24mm f1.4 GM 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 24mm f1.4 GM renders a very deep black against contra light. But you better watch out, when the light-source is just outside the corner as it can produce some streaks across the image:
All-in-all the Sony GM let’s you shoot confidently under adverse contra-light situations. The only drawback being that the Sony A7 body might add some colorful “teardrops” to very bright sunstars as can be seen above. Here is an example where you can clearly see the effect under daylight conditions. The coloration cannot be seen though with less bright light sources as the example below shows:
Next check out my sample images!Check prices on the Sony FE 24mm f1.4 GM at B&H, Adorama, or Wex. Alternatively get yourself a copy of my In Camera book or treat me to a coffee! Thanks!