CONTAX G BIOGON T* 21mm(Ms-optics)

Review and Photo example of Kyocera CONTAX G mount 21mm f/2.8.

Gallery

LEICA M typ240

LEICA M8/R-D1

Review

The Biogon 21mm F2.8 is an autofocus lens released by Kyocera with the Contax G2 in 1996. Here, we introduce a lens modified by Ms-optics (Miyazaki Optical) to Leica M mount (rangefinder camera rangefinder linked).

There are several types of lenses called Biogon 21mm, and this lens is different from the Biogon 21mm for Contarex and the Biogon 21mm for Cosina Zeiss ZM.

I also used this lens with the Contax G1 and Contax G2, but after selling them, I had MS-Optics (Miyazaki Optical) modify the lens to Leica M mount rangefinder linked. The modified lens uses the common helicoid for 21mm, called MS-21.

The main differences between the original lens and the Ms-optics modified lens are the following four points.

Fixing method of hood and filter frame
- The frame for attaching the filter to the original lens is fixed, so the filter does not rotate when focusing, so a square hood can be used and PL filters are easy to use. However, third-party square hoods and PL filters cannot be used at the same time.
- The lens barrel with the filter attached rotates when focusing on the modified lens, making it difficult to use square hoods and PL filters.
Aperture click stops
- The original lens has click stops for each aperture.
- The modified lens has a stepless aperture from F2.8 to F16.
Rangefinder rangefinder linkage
- The original lens is G mount, so it is autofocus (hereafter, AF).
- The modified lens is linked to the rangefinder of a Leica M camera.
Minimum shooting distance
- Original lens is 0.5m
- Modified lens is 0.7m

For the original G mount, adapters for major mirrorless cameras such as Micro Four Thirds, Fuji X, Sony E, Nikon Z, and EOS R are available. Some mirrorless cameras are also compatible with autofocus. However, there are no adapters for minor cameras, so if you change to a Leica M mount, you can use it with more cameras.

This lens has excellent backlight resistance, probably due to its good coating, and even in situations where sunlight penetrates the subject, you will rarely encounter mysterious light caused by flare or ghosting.

The lens configuration is as shown in the specifications below, and although it is symmetrical, the amount of penetration of the rear lens is suppressed. Nevertheless, compared to retrofocus type wide-angle lenses and wide-angle lenses for SLR cameras, since the rear lens is closer to the sensor surface, depending on the digital camera model, a purple color cast may occur in the peripheral parts of the captured image, which is particularly noticeable when photographing blue skies, and a color cast can be seen in the first image taken with the LEICA M typ240 in the sample images.

Biogon 21mm lens configuration for CONTAX G (scanned and traced from the lens manual)

There are five ways to deal with color cast:

Enjoy the results in monochrome
When shooting in color, boldly reduce the periphery
Choose a subject with a color that does not show noticeable cast (give up on blue skies)
Shoot with film
Choose a camera with little color cast

This color cast does not occur on the Elmarit 21mm F2.8, a retrofocus type with the same focal length of 21mm but with the rear lens farther away from the sensor surface, so like the Super-Angulon, it is a lens that is a little difficult to use when used with Leica M9, M, M10, etc.

When used with the EPSON R-D1 or LEICA M8, which have smaller sensor sizes, the problematic periphery is cut, so it is no longer a 21mm wide-angle lens, but it is an easy-to-use lens.

This may be due to insufficient research, but several manufacturers offer modified lenses for the Biogon 28mm, Planar 35mm, and Planar 45mm, but I have never seen a 21mm M-mount modified lens except from Ms-optics.

The original 21mm viewfinder that comes with the lens doesn’t offer very good visibility, but the latest Cosina Zeiss or Leica 21mm viewfinders will give you a clearer view.

Third-party lens hoods

This is a square lens hood that I bought when I was using the original Biogon 21mm for G.

It has a screw-in stopper, so it can be attached to any lens with a diameter of 57mm. The tip of the original Biogon for G is 57mm, so it is thought that this was made to match that.

As mentioned above, when the lens is focused on the original Biogon for G, the front part of the lens barrel only moves in a straight line and does not rotate, so a square hood like this hood can be used.

In addition, the outer diameter of the genuine Contax 55mm lens filter is 57mm to match the Biogon 21mm, so if the lens has a 55mm filter thread, this hood can be attached via this Contax 55mm filter.

However, when you turn the focus ring on the modified BIOGON 21mm, the front part of the lens rotates in sync, so this square hood also rotates. It is possible to use it by changing the position of the lens hood after determining the focus, but it is troublesome and impractical, so I do not use this hood. It’s a shame because I really like the look of this hood.

As an aside, if you want to use the original Biogon 21mm F2.8 and Planar 35mm F2 lenses with the Contax G1, you will need to update the camera.

There are used Contax G1 cameras for sale that have not been updated, and these two lenses cannot be used with these cameras.

To tell if your camera has been updated, if there is a green label on the film chamber, then it has been updated. The Contax G2 is pre-compatible with all Contax G lenses, so there is no need to worry about this.

Specification and Competitor

Name	HOLOGON	BIOGON	BIOGON	PLANAR	PLANAR	SONNAR	VARIO SONNAR
Focal length(mm)	16.5	21	28	35	45	90	35-70
Max aperture	8(fixed)	2.8	←	2	←	2.8	3.5-5.6
Min aperture	16(Attached filter)	22	←	16	←	22	←
Lens Construction	5elements in 3groups	9elements in 7groups	7elements in 5groups	←	6eleme0nts in 4group	5elements in 4groups	13elements in 8groups
Min distance(m)	0.3	0.5	←	←	←	1.0	←
Lens length(mm)	11	35.5	30.5	31.5	38.5	63.0	54.0
Max diameter(mm)	57	59	56	56	56	56	60
Filter size(mm)	– Dedicated ND filters are available. Changes to f/8 > 16 to alleviate peripheral light attenuation.	55	46	46	46	46	46
Weight(g)	120	200	150	160	190	240	290
Weight(g) M-mount	124	151	194 (222)*1	115	161	219 (259)*1	–
Release date	1994	1996	1994	1996	1994	1994	1999