Carl Zeiss C Biogon T* 21mm F/4.5 ZM

Ultra-wide angle prime lens • Film era • Discontinued

Abbreviations

C A lens with both compact and classic design.
T* The multi-layer coating is applied to the surface of lens elements. It boosts light transmission, ensures sharp and high contrast images, minimizes ghosting and flares.
ZM The lens is designed for Leica M / Zeiss Ikon 35mm rangefinder cameras.

Production details

Announced:September 2006
Production status: Discontinued
Production type:Mass production
Original name:Carl Zeiss C Biogon 4,5/21 ZM T*
System: Zeiss Ikon (2004)

Features highlight

Extreme AoV
Manual
10 blades
MF
Compact
Lightweight

Specification

Optical design
Focal length:21mm
Speed:F/4.5
Maximum format:35mm full frame
Mount and Flange focal distance:Leica M [27.8mm]
Diagonal angle of view:91.7° (35mm full frame)
75.5° (Leica M APS-H)
Lens construction:8 elements - 6 groups
Diaphragm mechanism
Diaphragm type:Manual
Aperture control:Aperture ring
Number of blades:10
Focusing
Coupled to the rangefinder:Yes
Closest focusing distance:0.5m (uncoupled focusing)
0.7m (coupled focusing)
Maximum magnification ratio:1:20 at the closest focusing distance
Focusing method:<No data>
Focusing modes:Manual focus only
Manual focus control:Focusing ring
Physical characteristics
Weight:190g
Maximum diameter x Length:⌀53×31mm
Accessories
Filters:Screw-type 46mm
Lens hood:Bayonet-type 1365-665 (rectangular)

*) Sources of data: Manufacturer's technical data ● Use your inner eye: lenses by Carl Zeiss booklet (November 2007) ● ZEISS ZM lenses booklet (PUB. EN_10_025_149III) ● Zeiss Ikon System: Individuality by Carl Zeiss booklet (PUB. EN_10_025_149).

Manufacturer description #1

Distagon T* 4/18 ZM and C Biogon T* 4.5/21 ZM

Two new, compact super wide angle lenses with M-bayonet from Carl Zeiss

Oberkochen, 2006-09-25.

Tailor-made for the Zeiss Ikon rangefinder camera and other cameras with Leica M-bayonet, Carl Zeiss will launch two new, particularly compact super wide angle lenses at Photokina 2006: Distagon T* 4/18 ZM and C Biogon T* 4.5/21 ZM.

Both lenses are based on highly sophisticated optical designs from Carl Zeiss and provide high image definition in high purity colors – without flare and ghosting. They both cover the full 24x36mm format and are suitable for both analog and digital photography. Even with digital sensors in the small APS-C format, they still cover very wide field angles. Both lenses are remarkably compact and light and are therefore ideal for mobile photography.

Like all lenses in the ZEISS ZM line, they feature a durable, full metal precision mount and engraved scales. The 10-blade shutter has precise stops in 1/3 steps. Optionally, the lenses are available with a black or silver finish.

Manufacturer description #2

The C in the C Biogon T* 4,5/21 ZM name stands for both ‘compact’ and ‘classic’, the latter referring to a legendary Zeiss design from 1952. Smaller and lighter than the Biogon T* 2,8/21 ZM, it is ideal for traveling and for photographing unobtrusively in public places. The lens is rangefinder-coupled for easy focusing and the optional 21 mm viewfinder is available for accurate image composition. The C Biogon T* 4,5/21 ZM is an ideal lens for many different wide-angle applications including travel, architecture, landscape and interior photography.

Manufacturer description #3

The C Biogon T* 4,5/21 ZM is an exceptionally compact and unique super wide-angle lens. Like its classic predecessor from 1952, the optical performance is stellar and destined to make the same history.

Updated with the most recent high performance optical glass types and the Carl Zeiss quality assurance methods, the image quality exceeds that of today's best color films and exhibits virtually no distortion. The 4,5/21 ZM has a filter size of only E46 and is remarkably small and lightweight, making it the ideal super wide-angle for traveling.

Typical application

landscapes, interiors, buildings, cityscapes, travel

Alternatives in the Zeiss Ikon system

Sorted by focal length and speed, in ascending order

Lenses with similar focal length

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35mm full frame

43.27 24 36
  • Dimensions: 36 × 24mm
  • Aspect ratio: 3:2
  • Diagonal: 43.27mm
  • Area: 864mm2

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Image stabilizer

A technology used for reducing or even eliminating the effects of camera shake. Gyro sensors inside the lens detect camera shake and pass the data to a microcomputer. Then an image stabilization group of elements controlled by the microcomputer moves inside the lens and compensates camera shake in order to keep the image static on the imaging sensor or film.

The technology allows to increase the shutter speed by several stops and shoot handheld in such lighting conditions and at such focal lengths where without image stabilizer you have to use tripod, decrease the shutter speed and/or increase the ISO setting which can lead to blurry and noisy images.

MF

Sorry, no additional information is available.

Original name

Lens name as indicated on the lens barrel (usually on the front ring). With lenses from film era, may vary slightly from batch to batch.

Format

Format refers to the shape and size of film or image sensor.

35mm is the common name of the 36x24mm film format or image sensor format. It has an aspect ratio of 3:2, and a diagonal measurement of approximately 43mm. The name originates with the total width of the 135 film which was the primary medium of the format prior to the invention of the full frame digital SLR. Historically the 35mm format was sometimes called small format to distinguish it from the medium and large formats.

APS-C is an image sensor format approximately equivalent in size to the film negatives of 25.1x16.7mm with an aspect ratio of 3:2.

Medium format is a film format or image sensor format larger than 36x24mm (35mm) but smaller than 4x5in (large format).

Angle of view

Angle of view describes the angular extent of a given scene that is imaged by a camera. It is used interchangeably with the more general term field of view.

As the focal length changes, the angle of view also changes. The shorter the focal length (eg 18mm), the wider the angle of view. Conversely, the longer the focal length (eg 55mm), the smaller the angle of view.

A camera's angle of view depends not only on the lens, but also on the sensor. Imaging sensors are sometimes smaller than 35mm film frame, and this causes the lens to have a narrower angle of view than with 35mm film, by a certain factor for each sensor (called the crop factor).

This website does not use the angles of view provided by lens manufacturers, but calculates them automatically by the following formula: 114.6 * arctan (21.622 / CF * FL),

where:

CF – crop-factor of a sensor,
FL – focal length of a lens.

Mount

A lens mount is an interface — mechanical and often also electrical — between a camera body and a lens.

A lens mount may be a screw-threaded type, a bayonet-type, or a breech-lock type. Modern camera lens mounts are of the bayonet type, because the bayonet mechanism precisely aligns mechanical and electrical features between lens and body, unlike screw-threaded mounts.

Lens mounts of competing manufacturers (Canon, Nikon, Pentax, Sony etc.) are always incompatible. In addition to the mechanical and electrical interface variations, the flange focal distance can also be different.

The flange focal distance (FFD) is the distance from the mechanical rear end surface of the lens mount to the focal plane.

Lens construction

Lens construction – a specific arrangement of elements and groups that make up the optical design, including type and size of elements, type of used materials etc.

Element - an individual piece of glass which makes up one component of a photographic lens. Photographic lenses are nearly always built up of multiple such elements.

Group – a cemented together pieces of glass which form a single unit or an individual piece of glass. The advantage is that there is no glass-air surfaces between cemented together pieces of glass, which reduces reflections.

Focal length

The focal length is the factor that determines the size of the image reproduced on the focal plane, picture angle which covers the area of the subject to be photographed, depth of field, etc.

Speed

The largest opening or stop at which a lens can be used is referred to as the speed of the lens. The larger the maximum aperture is, the faster the lens is considered to be. Lenses that offer a large maximum aperture are commonly referred to as fast lenses, and lenses with smaller maximum aperture are regarded as slow.

In low-light situations, having a wider maximum aperture means that you can shoot at a faster shutter speed or work at a lower ISO, or both.

Closest focusing distance

The minimum distance from the focal plane (film or sensor) to the subject where the lens is still able to focus.

Closest working distance

The distance from the front edge of the lens to the subject at the maximum magnification.

Magnification ratio

Determines how large the subject will appear in the final image. For example, a magnification ratio of 1:1 means that the image of the subject formed on the film or sensor will be the same size as the subject in real life. For this reason, a 1:1 ratio is often called "life-size".

Electromagnetic diaphragm control system

Provides highly accurate diaphragm control and stable auto exposure performance during continuous shooting.

Manual diaphragm

The diaphragm must be stopped down manually by rotating the detent aperture ring.

Preset diaphragm

The lens has two rings, one is for pre-setting, while the other is for normal diaphragm adjustment. The first ring must be set at the desired aperture, the second ring then should be fully opened for focusing, and turned back for stop down to the pre-set value.

Semi-automatic diaphragm

The lens features spring mechanism in the diaphragm, triggered by the shutter release, which stops down the diaphragm to the pre-set value. The spring needs to be reset manually after each exposure to re-open diaphragm to its maximum value.

Automatic diaphragm

The camera automatically closes the diaphragm down during the shutter operation. On completion of the exposure, the diaphragm re-opens to its maximum value.

Fixed diaphragm

The aperture setting is fixed at F/4.5 on this lens, and cannot be adjusted.

Number of blades

As a general rule, the more blades that are used to create the aperture opening in the lens, the rounder the out-of-focus highlights will be.

Some lenses are designed with curved diaphragm blades, so the roundness of the aperture comes not from the number of blades, but from their shape. However, the fewer blades the diaphragm has, the more difficult it is to form a circle, regardless of rounded edges.

At maximum aperture, the opening will be circular regardless of the number of blades.

Weight

Excluding case or pouch, caps and other detachable accessories (lens hood, close-up adapter, tripod adapter etc.).

Maximum diameter x Length

Excluding case or pouch, caps and other detachable accessories (lens hood, close-up adapter, tripod adapter etc.).

For lenses with collapsible design, the length is indicated for the working (retracted) state.

Weather sealing

A rubber material which is inserted in between each externally exposed part (manual focus and zoom rings, buttons, switch panels etc.) to ensure it is properly sealed against dust and moisture.

Lenses that accept front mounted filters typically do not have gaskets behind the filter mount. It is recommended to use a filter for complete weather resistance when desired.

Fluorine coating

Helps keep lenses clean by reducing the possibility of dust and dirt adhering to the lens and by facilitating cleaning should the need arise. Applied to the outer surface of the front and/or rear lens elements over multi-coatings.

Filters

Lens filters are accessories that can protect lenses from dirt and damage, enhance colors, minimize glare and reflections, and add creative effects to images.

Lens hood

A lens hood or lens shade is a device used on the end of a lens to block the sun or other light source in order to prevent glare and lens flare. Flare occurs when stray light strikes the front element of a lens and then bounces around within the lens. This stray light often comes from very bright light sources, such as the sun, bright studio lights, or a bright white background.

The geometry of the lens hood can vary from a plain cylindrical or conical section to a more complex shape, sometimes called a petal, tulip, or flower hood. This allows the lens hood to block stray light with the higher portions of the lens hood, while allowing more light into the corners of the image through the lowered portions of the hood.

Lens hoods are more prominent in long focus lenses because they have a smaller viewing angle than that of wide-angle lenses. For wide angle lenses, the length of the hood cannot be as long as those for telephoto lenses, as a longer hood would enter the wider field of view of the lens.

Lens hoods are often designed to fit onto the matching lens facing either forward, for normal use, or backwards, so that the hood may be stored with the lens without occupying much additional space. In addition, lens hoods can offer some degree of physical protection for the lens due to the hood extending farther than the lens itself.

Teleconverters

Teleconverters increase the effective focal length of lenses. They also usually maintain the closest focusing distance of lenses, thus increasing the magnification significantly. A lens combined with a teleconverter is normally smaller, lighter and cheaper than a "direct" telephoto lens of the same focal length and speed.

Teleconverters are a convenient way of enhancing telephoto capability, but it comes at a cost − reduced maximum aperture. Also, since teleconverters magnify every detail in the image, they logically also magnify residual aberrations of the lens.

Lens caps

Scratched lens surfaces can spoil the definition and contrast of even the finest lenses. Lens covers are the best and most inexpensive protection available against dust, moisture and abrasion. Safeguard lens elements - both front and rear - whenever the lens is not in use.