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Zeiss ZM 21mm f/4.5 C-Biogon T*

The Zeiss ZM 21mm f/4.5 C-Biogon (about $1117) is a relatively inexpensive, but strong performer in my brief field shooting. Its near-zero distortion is absolutely unique among 21mm lenses.

Composing with the 21/4.5 C-Biogon mandates use of the optional 21mm ZI viewfinder (about $364), same need as for any other 21mm offering. Which unfortunately raises the price by about a third.

View near real-time pricing and availability for Zeiss ZM an Leica M lenses on the Leica M gear page.


I found it easy to focus the ZM 21/4.5 accurately using the rangefinder. Rangefinder accuracy doesn't change with focal length, so precision should be excellent with a 21mm, and this is what I observed.

Image quality

Guide to Leica

Performance is very crisp and contrasty, with richly saturated color and excellent detail across most of the frame, even wide open.

Stopping down to f/5.6 yields outstanding results, but is hardly warranted, since performance varies little from f/4.5 to f/8; it’s more about vignetting, even so only a modest improvement is seen from f/4.5 to f/8.






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Per Zeiss. See the datasheet.

Zeiss ZM 21mm f/4.5 C-Biogon
Focal length: 21mm
Aperture scale: f/4.5 - f/22
Focusing range: 0.5m - infinity
Angular field, diag./horiz./vert 90/80/58°
Coverage at close range: 48 x 72 cm
Image ratio at close range:            1:20
Number of elements/groups: 8 elements in 6 groups
Filter thread: M 46 x 0.75
Weight: 190g
Dimensions (with caps): ø 53 mm, Length 31 mm


Distortion is stunningly low, the best of any 21mm lens, bar none. This offers unique possibilities for architectural type subjects. Unfortunately, its design means that off-center color shift is a problem for color photography, though not for black and white.

Absurdly low distortion of the Zeiss ZM 21/4.5 C-Biogon

Distortion is never a concern when shooting angular subjects with the 21/4.5 C-Biogon.

Leica M9 + Zeiss ZM 21/4.5 C-Biogon @ ~f/8

Aperture ring

As with the other ZM lenses, the 1/3 stop click stops feel fantastic, and they are easy to see. I love this aspect of the ZM line, and it’s practical too: it allows fine-tuning exposure to 1/3 stop, something that can be of use with digital (expose to the right). They are clear and well marked on the outside barrel of the lens, nicely done, and the slight clicks they make offer excellent auditory and tactile feedback.


The two-step is OK with some practice: focus, then compose with the hot-shoe mounted viewfinder.


The ergonomics are excellent, setting aside the need for a separate viewfinder. I really liked using this lens. It’s very compact, yet affords enough space for a natural grip on the focusing ring.

The lens hood is rectangular and does make the lens look larger than without, but it’s an effective hood, and worth using unless space is really at a premium.


The images below are presented at much larger sizes in my Guide to Leica.

Leica M9 + Zeiss ZM 21/4.5 C-Biogon @ ~f/8

Off-center color shift is evident above and below. See the black-and-white version below for comparison.

Leica M9 + Zeiss ZM 21/4.5 C-Biogon @ ~f/8

A black and white rendition below shows that the off-center color is just that— color. Black and white shooters will love this lens for its brilliance and outstanding sharpness.

Leica M9 + Zeiss ZM 21/4.5 C-Biogon @ ~f/8


I shot extensively with the 21/4.5 C-Biogon initially, and I really loved its performance in terms of distortion; it’s unheard of to find a 21mm lens that can render straight lines straight out to the corners.

I feel very comfortable shooting the 21/4.5 C-Biogon for black and white, and even for color I developed a layer mask to correct the off-center color shading (discussed with instructions in my review of the M9).

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