Thoughts on the Voigtlander Ultron 35mm ASPH II

Friday, 17 June 2022 16:09

The Ultron 35mm f/2 ASPH has been around since January 2019, but it was in March 2021 when Voigtländer released a redesign known as the Type II. While both types share the same optical design, Voigltänder updated the exterior design with the Type II while also making it an all brass build. I’ve had my copy since December 2021.

The lens promises a modern optical performance in a more “classic” design. Featuring eight elements in 5 groups as seen in the diagram below, with one Aspherical element (blue) and one “Abnormal Partial Dispersion” element (pink). What an Abnormal Partial Dispersion lens I don’t know; is it high refractive glass?

The Ultron’s compact size, feel and density is impressive. It’s a small lens, measuring 28.14mm (measured from mount flange to the front), but not too small to become fiddly to use. The solid brass build makes the lens feel very dense. I measured the weight at 229.6g with caps, and 211.6g without. Funny enough the Silver Summicron 35mm ASPH 11674 I had for a short time, weighed 240g without caps and hood. The Summicron is larger though.

My ownership of the Silver Summicron 35mm ASPH 11674 didn’t last long. My copy had a strong focus shift and harsh astigmatism off centre that would only calm down by f/8. It was an otherwise average lens at best. My experience is that the Ultron 35 ASPH outperforms the Summicron 35 ASPH II by quite a margin. 

After I returned the Summicron, I ordered the Color-Skopar 35/2.5 PII. The price was right, the size was good, and it had a reputation for good performance. When I got it, it certainly performed well. In fact it was an almost perfect pairing with my M10 Monochrom camera. Smooth and rich tonality, good contrast that wasn’t overwhelmingly strong and excellent resolution to boot. It just had one problem that I had no patience for, focus shift. It less severe than my Summicron 35mm ASPH, but it was enough to be frustrating. I became impulsive and after assessing some Ultron 35mm sample DNG files from a forum contact, I pulled the trigger and ordered the Ultron 35mm ASPH II. In hindsight, I should have had more patience and researched this some more. 

Unfortunately the Ultron’s image quality doesn't blow me away. There is no focus robbing focus shift, but other than that the images were rather unspectacular compared to the excellent Color Skopar 35/2.5 PII. If I only had the Summicron to compare it to, I would've been much happier.

Please don’t misunderstand, the Ultron 35mm isn't a bad lens. In fact it’s quite impressive in some areas. For my purposes though, it's not better than the Color-Skopar 35mm f/2.5 PII. However, optical performance isn’t everything and the Ultron does have better ergonomics than the overtly compact and fiddly Color Skopar 35mm.

The Ultron 35mm isn’t going to win any hearts with its out-of-focus rendering. The blur can be harsh and the vignetting is strong at wider apertures. Stopping down one or two stops does a lot to render a more pleasant blur and reduce the vignetting. The quality of the blur is very dependant on focus distance, the distance between subject and background and lastly the intensity of the light. For instance, the lens will do best at very close focus distances, where the subject is far removed from a uniformly lit low contrast background and where the focus transition can be avoided as much as possible. The focus transition zone from foreground to background blur can be prone to render harshly too, but it's definitely better behaved at closer rather than at medium to far focus distances. 

The background out-of-focus areas can show bright outlining of high contrast edges and blur discs, with chromatic aberration visible in these areas. The colour of this secondary chromatic aberration, including the lateral chromatic aberration, can be quite an unusual tint. Rather than the typical Cyan/Magenta chromatic error, it renders more a yellow-green and violet-purple tint. This yellow/green chromatic aberration is a rather unpleasant sickly shade and is harder to correct without influencing other colours in the image. Some longitudinal chromatic aberration is also present at wider apertures, featuring the typical magenta in the foreground and green in the background. Generally speaking, I would avoid shooting this lens at apertures wider than f/4 in very bright conditions. In less intense light environments the rendering can be quite pleasant, but it’s not a bokeh king by any standards. 

The high degree of optical vignetting does the out-of-focus rendering no favours, exaggerating the cat-eye affect and increasing perceived depth of field towards the edges. In some situations a slight swirlyness can come across the image as a result. For my use I doubt this will be an issue, but mileage may vary with photographers that prioritise wider aperture shooting. What bugs me the most is the vignetting or light fall off, which I think is way too much. There's no exposure difference between f/2 and f/2.5 and visually the only difference is a slight hot spot in the centre at f/2. 

Below is an example of just how ugly the blur can get at f/2 and the lighting wasn’t particularly harsh.

Stopping down the Ultron 35mm to f/2.8 improves the background blur quite a bit. The image below shows crops of strongly back-lit tree branches. The f/2.8 image shows a softening of the bright blur disc edges. At f/4 these soften up even more.

The Ultron 35mm is sharp at the centre from wide open, and very sharp by f/2.8. It's an impressive level of detail with the 60MP imager of the M11. The weakest point for this lens is in the mid-zone, especially for medium to far focus distances. The lens' cross-frame performance seems optimised for closer focusing distances, where mid-zone detail is smoother, sharper and with less astigmatism. I’ve not quite figured out where things start changing but I would say it's around the 3 meter mark (10 feet). For the medium to far distances, the mid-zone renders harshly with strong double edged detail at apertures wider than f/5.6. To me this looks like typical astigmatism and if one were to see a MTF chart for this lens I’m going to bet the sagittal and tangential lines for the finer details are diverged in this area. The difference can be quite staggering when comparing the entire focus plane between an image shot at 1 meter with one shot at 20 meters.

Not only is there this mid zone dip but there’s also slight moustache shaped field curvature. This makes shooting planar subjects and landscapes a little trickier. The image below illustrates the field of focus across the frame at different apertures, shot at a distance of about 2 meters. Open the image in a new window or tab to view it larger.

For planar subjects the best aperture to use will be f/8, but in many cases f/5.6 will be sufficient.  Take a look at the image below I photographed at f/5.6 on the Leica M11, followed by crops from the centre, mid-zone and edges. At f/5.6 and smaller the field of focus has evened out somewhat sufficiently to be almost a non-issue for planar subjects. In cases like the scene below, I focused on the distant trees instead of the water’s edge, which at f/5.6 places the mid-zone point of focus near the water’s edge. The centre’s depth of field is large enough to cope with the back focus. 

Crops of the above image. 

At f/5.6 and f/8, the Ultron 35mm is a an excellent performer on the M11. Very high resolving with excellent clarity and contrast throughout the frame. I have no complaints with image quality at these apertures, and any desire for something arguably better like the APO Lanthar 35/2, is superseded by the Ultron’s practical size and lower price. Below is an image shot at f/8 focused at the centre shoreline, followed by an actual pixels crop demarcated by a red rectangle.

The Ultron 35mm is quite resistant to flare thanks to Voigtländer’s excellent multi-coatings. I’ve used the lens in a number of sittuations against strongly backlit scenes and rarely did flare get in the way of the shot. Sometimes flare can sneak in unexpected sittuations when the light source is outside of the frame. I suspect the highly reflective silver chromed bayonet and filter thread is the culprit here. A screw on filter helps to reduce its occurrence. This silver chromed front end is a design choice that Zeiss and Voigtländer have been criticised for quite often. With the release of the Voigtlander Nokton 50mm f/1.0 ASPH we see a black fitler thread and bayonet mount. Perhaps a sign of whats to come?

As seen above, flare is well controlled even in very high contrast sittuations. Also, the slight barrel distortion is discrete enough to not need correcting most of the time. I’ve not used distortion correction once with this lens. On the M system, there is little to no colour shading at the edges, but the images without coding render a little cooler at the edges., It’s less than with the Color-Skopar 35/2.5 Pii or even the Summicron 35/2 ASPH 11673. This makes selecting a lens profile in camera a little tricky. I don't recommend using the 35 f/2 ASPH 11879/11882 which makes the edges a little magenta. I would recommend rather using the 35 f/2 11310/11311 lens profile. Even coding the lens to the Leica APO Summicron 35mm ASPH, with the 6bit code 001101, also works. I find a cyan/blue shift is a little more pleasant than a magenta shift.

Take a look at the images below showing the vignette and shading correction between the two mentioned lens profiles and the uncoded image at the centre. The images were shot at f/8, White Balance corrected at the centre for each image. The bottom row shows the same images but with saturation increased to exaggerate the colour differences. 

The Voigtlander Ultron 35/2 ASPH II is with no doubt a high performing modern lens in a compact and good looking package. Performance is very good on the Leica M11 but it takes stopping down to get there. I appreciate the small compact nature of the lens, which is more important to me than outright image perfection and probably the biggest reason I’m not interested in the Voigtlander APO Lanthar 35/2. If anything, I’ll give the Ultron 28mm/2 ASPH II a try, but I prefer a 35mm focal length.

My biggest gripe with the lens is its mid-zone performance at medium to far distances at apertures wider than f/5.6. I would call it downright ugly and harsh. Secondly, the strong light fall-off is a little obnoxious and contributes to a look some might feel objectionable; A slight swirl with increased depth towards the edges. 

I can recommend the Ultron 35mm ASPH II if its compact size and ergonomics are appealing and if shooting stopped down doesn’t bother you. It’s still priced well, but I would advocate serious consideration for the Color Skopar 35/2.5 PII also, which comes in at half the price!!! The Ultron’s f/2 aperture is deceptive and offers as good as zero benefit over the f/2.5 lens due to the heavy fall off of the Ultron.

Leica M11 with the Voigtlander Ultron 35/2 ASPH II. Aperture f/2.8

Leica M11 with the Voigtlander Ultron 35/2 ASPH II. Aperture f/4

Leica M11 with the Voigtlander Ultron 35/2 ASPH II. Aperture f/2