Three 21 mm lenses for Leica-M

Compared: Biogon and both Super-Angulons

Carl Zeiss 21 mm f 4.5 Biogon	First version, introduced in 1955 (later version is part of the Contax G line.) Can be found on Leica mount, though usually without rangefinder coupling. Uses a __ mm filter, and the front-heavy / deep-seating Contax mount makes it somewhat bulky when mounted on a Leica body. Aperture ring rotates with focus and has no detents. Full range focus adjustment rotates apx 300 degrees.
Schneider 21 mm f 4 Super-Angulon	First version, introduced in 1958 Takes current 39 mm filters - this is really small for such a wide lens! A removable M-mount allows the lens to be used on screw-mount bodies as well. The real drawback for users is the aperture ring. The ring rotates with focus, and the f-stops are not at regular intervals (common with earlier lenses). And of course, this lens will not meter on the M-6.
Schneider 21 mm f 3.4 Super-Angulon	Second version, introduced in 19__ This lens has one less element than the 1st version, but the same number of groups. From a user's perspective, this lens should be favorable as the f-stop ring is stationary and has regularly-spaced intervals. Uses a __ mm filter, but otherwise very close in size to the 1st version.

Two rolls of Ektachrome 100 were used, one for each maker's body. First, however, each roll was started in the Leica with identical calibration exposures. This ensured that film process variations could be reconciled. One of the rolls was then transfered to the Contax and the tests began. Unfortunately, there were a few things I wanted to test for and could not. I had to burn film in exposure bracketing just to match the two different shutters, and thus did not have enough film for everything. I did not test for corner falloff or flatness of field. Also, most exposures were checked at the center and extreme f-stops, but not all f-stops.

	This is a pure white ceiling with glass bricks under hazy sunlight. I wanted to check the color balance of the lenses, so I exposed this as a gray card. Some Ziess vs Leitz lens tests have shown a slight tan vs green shift between the two makers. However, I can't find any color shift between these three lenses with this exposure.
This Thai building has intricate detail throughout, including ceramic and gold tiles along the roof edge. (The cars are stationary.)	At wide-open settings, the 1st and 2nd SA had slightly more falloff than the Biogon, in the sky from the valley between left and mid roofs to the upper-right frame corner. This was first noticed with eye/brain, and then verified with an incident light meter on the projection surface.
Flowers, Buddha, and gold are all placed to honor deceased relatives. There is very fine detail in the painting behind the Buddha. The abundant gold tones are rendered in semi-metallic paint.	At f 4.0, my wife noticed that the Buddha's face seemed to have more "3-dimensional" effect with the 1st SA than with the 2nd. Also, with the 2nd SA, the black/green leaves painted on the wall were cast slightly more green, and with the 1st SA more brown. It's as if the 1st SA was responding better to the yellow tones than the 2nd. At this wide-open setting, both lenses had good sharpness / flatness, as the middle candle is in focus and the lower candle, in the same vertical plane, is also in focus. Both SA's showed extremely good detail and flare control at this aperture. (Zeiss not included at this f-stop). At f 11, all 3 lenses were compared. There was slightly less corner falloff with the Biogon, noticable only on the painted wall at the top of the frame. With the Biogon, the small areas of intense red behind the Buddha's shoulders seemed more vivid than with the Super-Angulons. The Super-Angulons seemed to have the same color of red there, but the Biogon's reds seemed to be more in "in focus". Also at f 11, I noticed a leaf in the painted detail which had green, black outlines, and a slice of white. This particular leaf was an excellent test of the lenses' resolution, with high contrast and size close to the resolution limit. With the 2nd SA, the black outlines were distinctly visible. With the 1st SA, the same black outlines were still there but perhaps less prominently. With the Biogon, the black outlines were soft, and would not have been noticed at first without the help of the Super-Angulons. Perhaps related to observations of resolution, I noticed something about the incense sticks. The sticks are colored a deep red, and are placed in a crucible of gray ash. With the Biogon, each red stick had a dark edge running down the left side. The incense sticks are very thin, and the tiny dark edges would ordinarily look like shading. With the 1st SA, the sticks and the ash background had the same colors, but there were no dark edges. I believe that the rendering by the SA is correct. The dark edges on the Biogon seem to indicate a shift between colors which the SA does not exhibit. This same shift may be responsible for a well-defined edge between the Buddha's golden elbow and vivid red background, as seen through the Biogon. Neither SA had quite the same definition between those colors at the same point. Except for the notes above, these three lenses were extremely close in performance for this image.
A large shopping center with deep shadows and point-sources of light throughout.
These ornate spirit houses are found throughout Thailand.

After cycling through these images for countless hours, I can say that all three of these lenses are very good and very close to each other. In most cases, the differences are elusive. Of all the performance factors listed above, perhaps the most important to the photographer is the corner falloff of the Super-Angulons. However, far more real-world difference between these lenses would be introduced on a given day, such as with exposure variation, camera shake, and of course timing and composition... If you are considering obtaining any of these lenses, you might find certain "user" factors to be more dominant than the differences in optics. The Biogon in a Leica mount probably does not have rangefinder coupling. The Biogon and the 1st Super-Angulon have f-stop scales which rotate with focus, and only the 2nd Super-Angulon has a stationary f-stop ring with regular intervals. The 1st Super-Angulon is generally more expensive than the 2nd, but it is smaller and its sharing of the 39 mm filter is a plus.

Many thanks to Eddie and the Crew at Camera Collection in Bangkok. They carry a large selection of classic 35 mm camera equipment.