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. Although being designated as an apochromatic design the Voigtländer still shows a bit of loCA up to f2.8. This is slightly stronger than from the Zeiss Otus but weaker than from the Z-Nikkor and much better than the Sony ZA.
When stopping down background and foreground become equally sharper. So there’s no focus shift when you acquire focus at f2.0 and then take the shot stopped down.
The following real life shot under harsh contra-light conditions shows that the Voigtländer produces only faint green coloration in the background and no purple fringing around high-contrast edges in the focus plane. And spill-over from the extra-bright background into the subject is also well controlled:
Sharpness and contrast
Let’s have a look at the theoretical performance of the Voigtländer 50mm f2 APO-Lanthar and compare it to the performance of the Nikon Z 50mm f1.8 S, Sony FE 55mm f1.8 ZA, and Zeiss 55mm f1.4 Otus:
The MTF chart of the Voigtländer shows the computed contrast-curves without influence of diffraction at 10 line-pairs/mm (top), 30 lp/mm (middle), and 40 lp/mm (bottom). The Nikon charts shows 10/30 lp/mm (red/blue), the Sony and Zeiss charts show 10/20/40 lp/mm from top to bottom. Higher values are better (more contrast) and the closer the dotted and solid lines are together the less contrast dependents on the orientation of the test-pattern (less astigmatism). 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/DX-corner), and 20 mm (FF/FX-corner) on a 45MP Nikon Z7 body or 42MP Sony A7R II.
At 10 lp/mm all four lenses perform pretty similar and you should not find flaws with overall contrast – with the slight exception of the Sony ZA in the FF-corner. But when looking at finer details the Voigtländer pulls ahead: At 30 lp/mm it tops the Z-Nikkor and at 40 lp/mm it’s better than even the mighty Otus.
Let’s see how this theoretical performance of the Voigtländer translates into real life results in the sharpness test based on Siemens-stars. Processing was done in Lightroom 11.4.1/CRAW 14.4.1 from RAW to Adobe Color profile with the built-in lens profile applied where available. 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 Voigtländer 50mm f2 APO-Lanthar from f2.0 down to f11 without application of any lens correction – not even for lateral CAs. For comparison I used the Nikon Z 50mm f1.8 S and Zeiss 55mm f1.4 Otus (both shot on a Nikon Z7) plus the Sony FE 55mm f1.8 ZA shot on a Sony A7R II. With linear resolution of the 45MP Z7 sensor only 4% higher than from the 42MP A7R II, identical test set-up and identical RAW processing (except for the use of the built-in lens-profiles for the mirrorless lenses) the comparability between the test-shots should be very good.
Wide open the Voigtländer 50mm f2 APO-Lanthar produces excellent sharpness in the APS-C/DX image circle – and the FF/FX corner is already very good. The other lenses are pretty close in the center but further outside they clearly fall behind the Voigtländer. Regarding field-curvature: The Voigtländer shows no field curvature at all: All crops in a row come from the same shot. Stopping the lens down to f2.8 sharpens the FF/FX-corner of the Voigtländer a bit and reduces the slight coloration in the center – which only shows how sharp the lens already is wide open.
Performance at long distances
The Siemens-star test-targets are shot at a distance of 45x focal length (i.e. at around 4m for 85mm focal length). 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 11.4.1/CRAW 14.4.1 from RAW to Adobe Color profile with the built-in lens-profile applied where available. On the Voigtländer I used Adobe’s lens profile. Noise-reduction is set to 0, sharpening to 50/0.5/36/10, with no extra tone, color, or saturation adjustment. I used manual focus at the largest aperture on all lenses in this comparison and did not change focus for other apertures. All shots were made at base ISO and image stabilization switched off.
The following image shows the complete scene wide open to give you an impression of the angle of view. Following the main image are 100% crops from the center, APS-C/DX-corner, and FF/FX-corner from the Voigtländer 50mm f2 APO-Lanthar compared to the Nikon Z 50mm f1.8 S and Sony FE 55mm f1.8 ZA. The Z-Nikkor and the Sony ZA were shot at a different day – but with roughly comparably atmospheric conditions. As usual I have selected the diagonal that provided the better corner results as almost any lens is a bit decentered – although to be fair, the Voigtländer was very well centered.
You can access the large originals but please respect our copyright and only use those images for personal use.
Again the Voigtländer 50mm f2 APO-Lanthar performs beautifully across the full frame already wide open. Differences between the three lenses in the center are minimal with the Sony ZA exhibiting a tiny bit of purple fringing at high contrast edges. At the APS-C corner the Sony ZA is softer and in the FF/FX-corner the Z-Nikkor is less sharp wide open than the other two. Stopping the Voigtländer down to f2.8 visibly reduces vignetting but otherwise does little to improve acuity any further.
Vignetting and distortions
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 Voigtländer 50mm f2 APO-Lanthar at different apertures. All images were developed to the same brightness in the center. As the Voigtländer lens does not come with an integrated lens profile the JPGs straight out of camera are not influenced by the setting for vignette control (or auto distortion control) in camera.
The sample images above show that without lens profile vignetting of the Voigtländer is very strong wide open and still visible at f2.8. Adobe’s lens profile set to 100% lifts the extreme corners about 0.8 EV at f2.0.
Distortions are of a mild pin-cushion type but are pretty well corrected with Adobe’s lens profile:
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 colour-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/FX-corner of the Voigtländer at various apertures:
The Voigtländer 50mm f2 APO-Lanthar shows very little coma at f2 and f2.8. From f4.0 onwards the lens produces more diffraction spikes than coma.
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.
The crops below the main image are from the center, APS-C/DX-corner, and FF/FX-corner resized to make them comparable across all my reviews.
The diameter of the Bokeh balls in the center is determined by the entrance pupil of the lens: Thus the Voigtländer produces slightly smaller Bokeh balls than a 50mm f1.8 lens (at identical magnification). But despite the disadvantage in size the Voigtländer produces Bokeh balls that are evenly lit with no onion rings, only a faint outline, and very little loCA. But cat’s eye effect towards the corners is clearly visible even in the APS-C/DX-corner at f2.0 and still visible at f2.8. The aperture blades of the Voigtländer are perfectly rounded at f2.0 and f2.8 but at other apertures the aperture blades show up in the circles of confusion. Although to be fair: twelve aperture blades make for a nicer approximation of a circle than seven or nine.
Now let’s see how this analysis of out-of-focus point-light sources translates into Bokeh-performance shooting a book-shelf. Again, the crops of the foreground, the middle-ground, and the background below the main image are resized to make them comparable across all my reviews.
Of the three lenses in this comparison the Z-Nikkor produces the softest Bokeh although the Voigtländer is pretty close in the background. The Sony ZA suffers from green coloration in the transition zone and its background looks pretty busy.
Looking at another crop (now at 100%) from the same images showing the ruler reveals a slight tendency for double contours of the Voigtländer. But they seem to be limited to the transition-zone and didn’t show up prominently in my sample images.
The Voigtländer 50mm f2.0 APO-Lanthar achieves a maximum magnification of 1:6.4 at minimum object distance. The area of sharp focus is just 154 x 230mm. The images shown below are 100% crops from 0mm, 11mm, and 20mm off the center of the sensor respectively.
The Voigtländer 50mm f2.0 APO-Lanthar is already quite sharp at f2.0 but stopping down to f4.0 yields very sharp results. Only the FF/FX-corner profits from stopping further down to f8.0. Field curvature is negligible even at minimum object distance.
Flare, glare, 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 Voigtländer 50mm f2 APO-Lanthar for these artifacts I went through a series of well calculated shots against a strong light source to provoke glare and ghosting. The lens hood was mounted in all shots. Following are some of the more extreme example results. The little bright square inset in the upper left 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:
The Voigtländer does produce a bit of flare, glare and ghosting especially when the light-source is close to the center, but the images keep a very deep black outside the immediately affected areas. And the often annoying streak when the light-source is just outside the corner is very moderate.
The Voigtländer 50mm f2 APO-Lanthar has 12 intricately curved aperture blades: The aperture is perfectly circular at f2.0 and f2.8 and thus does not produce sunstars at those settings. But at every other aperture (even at f2.2) the lens produces 12 well defined diffraction spikes. As usual the spikes become longer the more you stop down:
Next check out my sample images!Check prices on the Voigtländer 50/2 APO-Lanthar at B&H, Adorama, WEX UK or Calumet.de. Alternatively get yourself a copy of my In Camera book, an official Cameralabs T-shirt or mug, or treat me to a coffee! Thanks!