Carl Zeiss Distagon [T*] 40mm F/4 C

Ultra-wide angle prime lens • Film era • Discontinued

Abbreviations

T* Multi-layer anti-reflection coating is applied to the surfaces of lens elements. This anti-reflection coating increases light transmission, eliminates flare and ghosting, and maintains color consistence among all lens models.
C A lens with Compur shutter.

Model history (4)

Carl Zeiss Distagon [T*] 40mm F/4 CA10 - 90.50mB104
Carl Zeiss Distagon T* 40mm F/4 CFA11 - 100.50m 1982 
Carl Zeiss Distagon T* 40mm F/4 CFEA11 - 100.50mB93 1998 
Carl Zeiss Distagon T* 40mm F/4 IF CFEA12 - 90.50m 2003 

Features highlight

6x6
Extreme AoV
LS
MF
Auto
B104
filters
TC

Specification

Production details:
Announced:<No data>
Production status: Discontinued
Original name:Carl Zeiss Distagon 1:4 f=40mm
Carl Zeiss Distagon 1:4 f=40mm T*
System:Hasselblad V (1957)
Optical design:
Focal length:40mm
Speed:F/4
Maximum format:Medium format 6x6
Mount and Flange focal distance:Hasselblad V [74.9mm]
Diagonal angle of view:89°
Lens construction:10 elements in 9 groups
Diaphragm mechanism:
Diaphragm type:Automatic
Aperture control:Aperture ring (Manual settings only)
Built-in leaf shutter:
Type:Mechanical Synchro-Compur
Range of shutter speeds:1 - 1/500 + B
Self-timer (V):Yes
Shutter speed control:Shutter speed ring
Cross-coupling control:Catch for disengaging cross-coupling
Flash sync mode:M & X sync
Flash sync terminal:Yes
Focusing:
Closest focusing distance:0.5m
Magnification ratio:<No data>
Focusing modes:Manual focus only
Manual focus control:Focusing ring
Physical characteristics:
Weight:1375g
Maximum diameter x Length:⌀104×124.5mm
Accessories:
Filters:Bayonet-type 104
Lens hood:Ø104/40 40290 - Bayonet-type square
Teleconverters:Carl Zeiss PC Mutar T* 1.4X → 56mm F/5.6
Carl Zeiss Mutar T* 2X → 80mm F/8
Hasselblad Converter 2XE → 80mm F/8
Sources of data:
1. Manufacturer's technical data.
2. Hasselblad 500EL/M, SWC/M, 2000FC, 500C/M booklet (December 1980).
3. Hasselblad Product Catalog (November 1977).
4. Hasselblad 500EL/M, SWC, 2000FC, 500C/M booklet (December 1977).
5. Hasselblad Product Catalog (December 1978).
6. Hasselblad Product Catalog (December 1979).
7. Hasselblad Product Catalog 1983/84 (December 1982).
8. Hasselblad Product Catalog (December 1967).
9. Hasselblad Product Catalog (December 1968).

Manufacturer description #1

For over $1,000 you can buy our 40mm Zeiss Distagon f/4 lens, and a camera to go with it.

The lens alone costs about as much as the entire Super Wide C camera, and you still need a body and film magazine.

It costs what it does because the Distagon is a very remarkable lens.

It had long been thought that 50mm was the practical limit in building a fast, wide angle lens for a 2 1/4" reflex camera. Which limited the angle of view to 75°.

The Distagon broke the rules. It added another 13° to the angle of view, and proved to be as distortion-free as our 38mm Biogon.

But the biggest advantage of the Distagon lens is that it fits the Hasselblad 500 C and 500 EL cameras. So you can look through the large ground glass and see what's in and what's out of focus, how vertical the verticals are and what kind of perspective the finished picture will have.

The Distagon lens also interchanges with nine other Carl Zeiss lenses, up to 500mm tele-photo.

And allows you to utilize all the backs and accessories of The Hasselblad System.

Both the 38mm Biogon and 40mm Distagon lenses are very much alike in terms of quality. Both lenses have built-in Compur shutters, so you can shoot at any shutter speed with any type of flash. Which is only possible when the shutter is in the lens - instead of in the camera.

The big difference between these two wide angle lenses is that one permits reflex viewing and one doesn't. And it's up to you to decide how much that's worth to you.

Manufacturer description #2

The Distagon T* f/4-40 mm with its angular field of 88° covers almost the same object field as the Biogon for the Hasselblad Superwide Camera.

In spite of the extraordinary technical features of this lens - speed, angular field and a long back focal distance compared with the focal length - the distortion could be kept remarkably small, an outstanding feature because the correction of wide-angle lenses of excessively long back focal distances is very difficult. The lens can also be used for architectural photography. The Distagon T* f/4-40 mm is especially suited for the photography of interiors, machines and models and for press photography.

The distance setting ring of this lens has a click stop at 0.9 m, which must be by-passed for photographs in the range from 0.9 m to 0.5 m. This stop position is meant to remind the user that he must stop down at distances below 0.9 m.

Manufacturer description #3

With an 88° angular field, the 40mm Distagon has almost the same angle of view as the 38mm Biogon. The difference between these nearly equivalent lenses lies in the fact that the Biogon is permanently attached to a camera body, whereas the 40mm Distagon can be used with the 500C/M, 500EL/M or 2000FC cameras. And with a focusing screen at his disposal, the photographer has full control over the composition of his image. He can also easily check out depth-of-field and perspective. The 40mm Distagon is a retrofocus design so as to provide space for the mirror between the rear lens element and the focal plane.

The 40mm Distagon displays exceptional correction for all aberrations, but its optical properties are at their best when the lens is used at long lens-to-subject distances. A detent on the focusing ring reminds the photographer that the lens should be stopped down to obtain the best results at distances under 35 in. Details calling for maximum resolution should be located at the center of the field, since resolving power falls off towards the corners with the lens wide open - but only at the shortest lens-to-subject distances. Despite this slight limitation, combining the 40mm Distagon with a 10 mm or 21 mm extension tube may sometimes prove useful. The technical results will be satisfactory, and the imagery may be especially exciting with exaggerated perspective and wide depth-of-field. The foreground, which is naturally the main subject, predominates.

Manufacturer description #4

The Distagon 40mm f/4 is an extreme wide-angle lens. With an 88° diagonal and 69° horizontal angle of view, it covers nearly the same field as the Biogon lens on the Hasselblad SWC. In contrast to the Biogon lens, however, the Distagon is an extreme retrofocus design. This means that it leaves enough room for mirror movement in a single-lens reflex camera, despite the wide angle of view. The lens is also remarkably fast for its type. It also features excellent correction of all aberrations, thereby ensuring a high standard of image quality. Even correction for distortion, previously regarded as a weak point in the retrofocus design, has been very successful. The glass used in this lens does not pass ultraviolet radiation, so an ultraviolet filter is not necessary. But don't forget the lens shade. Filters are attached to the front bayonet mount in the customary manner.

Practical experience has shown that the 40mm Distagon on the camera, despite its size and weight (48 oz), rests nicely in the hand and is by no means front-heavy. Being able to determine composition and depth-of-field on a focusing screen prior to exposure is a big advantage for the photographer. Obtrusive lines or perspective distortion can then be avoided or accentuated as the case may be. A Hasselblad spirit level (attached to the accessory rail) is recommended when exact camera levelling is necessary. The lens has been corrected for optimum performance at long lens-to-object distances. But it can also be used for close-up work. There is a detent on the focusing ring at the 3 ft setting (0.9 m) to remind the photographer of the need to stop down the lens in order to obtain the best optical results at close focusing distances. The diaphragm can be stopped down to f/32 if extreme depth-of-field is required. Objects in need of maximum resolution should be placed at the center of the field, since sharpness declines toward the corners of the image at the closest focusing distances.

The 40mm Distagon opens up dramatic new perspectives for adventurous photographers. Exciting results can be obtained.

From the Hasselblad House magazine (3/1971)

Changing from a normal angle lens to an extreme wide-angle lens may give you a few new ideas about approaches to exciting perspective and subjects. A wide-angle lens offers more than just the possibility of achieving special effects. It provides a whole new way of photographically viewing the world.

The Hasselblad photographer has three options: the Hasselblad Super Wide C with a 38 mm f/4.5 Biogon lens (90° angle of view), the 40 mm f/4 Disiagon lens (88° angle of view) or the 50 mm Distagon lens (75° angle of view).

The Hasselblad SWC is a special-purpose camera which does not have the reflex viewing system of the other Hasselblads. It has a permanently attached lens, a spirit level and a removable optical viewfinder.

The 40 mm or 50 mm Distagon lenses can be used with the Hasselblad 500C, 500C/M, 500EL and 500EL/M. The perspective provided by the 50 mm Distagon with a 75° angle of view is less extreme than the 40 mm Distagon’s, whose 88° angle of view makes it an extreme wide-angle lens.

The 40 mm Distagon, like the other Hasselblad lenses, is made by Carl Zeiss, West Germany. It has 10 elements in 9 groups. Its focusing range is from 19 3/4" (0.5 m) to infinity. It has a Synchro-Compur leaf shutter which is synchronized for expendable and electronic flash at all speeds from 1—1/500 sec., has "B" and "T" settings for time exposures and a self-timer. Automatic depth-of-field indicators provide fast information on depth-of-field. The diaphragm and shutter are cross-coupled and are read from the same index marker as distance settings, making it easy to check out all settings at a glance.

The 40 mm Distagon is a massive lens with an impressive front element. But despite its 46 oz. (1.3 kg) weight, the lens is well-balanced when mounted on the camera and is naturally supported by the hand without being front-heavy. It’s also fast and easy to work with. The photographer can use the focusing screen to evaluate picture impact, compose his subject and determine both the plane of sharpness and depth-of-field. The sharply converging lines and distorted perspective which so easily arise at the edges of the field when using a lens with such an extreme angle of view are readily visible through the viewfinder and can, thus, be avoided. But if the camera has to be absolutely horizontal, the use of the Hasselblad spirit level is recommended. It fits into the accessory shoe.

The manually released locking device on the focusing ring is the only control not found on the other Hasselblad lenses. This device is to remind the photographer to stop down for best results at focusing distances of less than 37" (0.95 m). Moreover, objects demanding maximum sharpness should be placed in the center of the field, since the lens does not provide maximum resolving power at very short focusing distances.

Like many lenses, the 40 mm Distagon was corrected for optimum performance when focused on infinity.

If this is kept in mind, the 40 mm Distagon can be used without any problems at reproduction ratios ranging from 1:20 to 1:8. Extension rings can be used with the 40 mm Distagon but are not recommended, even if they can produce interesting results. The lens can also be stopped down to f/32, a useful feature when extra depth-of-field is needed in wide-angle work, close-up work in particular. This extreme depth-of-field can produce results difficult to achieve in any other way.

Illumination is very even for a wide-angle lens, if the 40 mm Distagon is stopped down to f/8. Thanks to excellent optical correction for light fall-off, the corners of the field are as strongly exposed as the center.

The familiar phenomenon of darkening skies purple tinging in the corners when using some wide-angle lenses with color film never arises with the 40 mm Distagon, since the lens has the same color correction as the other Hasselblad lenses. Thus, color slides taken on the same film with different Hasselblad lenses display the same color characteristics.

The types of glass used in the lens also absorb ultraviolet light. Therefore, no UV filter is necessary. Otherwise, filters are attached to the bayonet mount in the usual way.

Many photographic assignments cannot be tackled using lenses with conventional angles of view. The extreme wide-angle of the 40 mm Distagon comes in very handy when you have to shoot in cramped spaces or shoot very wide subjects.

Fashion and advertising photographers have long made use of short focal length lenses. These lenses increase the fashion photographer’s chances of new and unusual angles which bring out the model or the garment while still taking in some background. If the photographer also uses the 40 mm Distagon with a Hasselblad 500EL and magazine 70, he has himself an electrically operated wide-angle camera with a large film capacity, making it unnecessary to break off the vital contact between model and photographer as frequently in order to make disturbing film changes.

The wide-angle lens is also invaluable to the news photographer who has to work smoothly and discretly. He can grab "blind" shots of people and situations, capturing relaxed and natural poses in that way. The Hasselblad’s 2 1/4"-square format makes enlargements of details easy.

The 40 mm Distagon provides new, creative opportunities for you to escape from humdrum photographic routine. Using it and other accessories in the Hasselblad system, you can build yourself the ideal camera for just about any photographic application calling for a wide-angle lens.

Carl Zeiss C series

The first generation of Carl Zeiss lenses with a built-in leaf shutter, introduced in 1957.

  • Synchro-Compur leaf shutter with self-timer (V);
  • Fully synchronized for M- and X-settings so that you can work with flash at all shutter speeds;
  • Aperture and shutter speed are cross-coupled by default but can be set independently for complete creative control;
  • Originally matt-chromed, all C lenses were supplied in black trim from 1969 to 1981;
  • T* multi-coated from 1973 (30-80mm focal length range), 1974 (all focal lengths).

Frequently asked questions (1)

  • What does the Carl Zeiss lens designation "Distagon" mean?

    The Distagon retrofocus design was specially developed to enable the use of extreme wide-angle lenses on SLR cameras. As the back focal distance can be made considerably longer than the lens focal length, it allows the motion of the reflex finder mirror in the free space between the last lens element and the film plane. The Distagon lenses - characterized by extraordinary speed and angle of view - provide remarkably good correction of all aberrations and thus excellent image quality. Through the use of floating lens elements (FLE) it has been possible to achieve high image quality and field flatness even in the close focusing range. The Distagon CFi 3.5/30 mm fish-eye lens features the widest diagonal angle of view in medium format - 180°. / Source: Hasselblad literature /

Other ultra-wide angle prime lenses in the Hasselblad V system

Sorted by focal length and speed, in ascending order

Hasselblad V mount (3)
Carl Zeiss Distagon T* 40mm F/4 CFA11 - 100.50m 1982 
Carl Zeiss Distagon T* 40mm F/4 CFEA11 - 100.50mB93 1998 
Carl Zeiss Distagon T* 40mm F/4 IF CFEA12 - 90.50m 2003 
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Chromatic aberration

There are two kinds of chromatic aberration: longitudinal and lateral. Longitudinal chromatic aberration is a variation in location of the image plane with changes in wave lengths. It produces the image point surrounded by different colors which result in a blurred image in black-and-white pictures. Lateral chromatic aberration is a variation in image size or magnification with wave length. This aberration does not appear at axial image points but toward the surrounding area, proportional to the distance from the center of the image field. Stopping down the lens has only a limited effect on these aberrations.

Spherical aberration

Spherical aberration is caused because the lens is round and the film or image sensor is flat. Light entering the edge of the lens is more severely refracted than light entering the center of the lens. This results in a blurred image, and also causes flare (non-image forming internal reflections). Stopping down the lens minimizes spherical aberration and flare, but introduces diffraction.

Astigmatism

Astigmatism in a lens causes a point in the subject to be reproduced as a line in the image. The effect becomes worse towards the corner of the image. Stopping down the lens has very little effect.

Coma

Coma in a lens causes a circular shape in the subject to be reproduced as an oval shape in the image. Stopping down the lens has almost no effect.

Curvature of field

Curvature of field is the inability of a lens to produce a flat image of a flat subject. The image is formed instead on a curved surface. If the center of the image is in focus, the edges are out of focus and vice versa. Stopping down the lens has a limited effect.

Distortion

Distortion is the inability of a lens to capture lines as straight across the entire image area. Barrel distortion causes straight lines at the edges of the frame to bow toward the center of the image, producing a barrel shape. Pincushion distortion causes straight lines at the edges of the frame to curve in toward the lens axis. Distortion, whether barrel or pincushion type, is caused by differences in magnification; stopping down the lens has no effect at all.

The term "distortion" is also sometimes used instead of the term "aberration". In this case, other types of optical aberrations may also be meant, not necessarily geometric distortion.

Diffraction

Classically, light is thought of as always traveling in straight lines, but in reality, light waves tend to bend around nearby barriers, spreading out in the process. This phenomenon is known as diffraction and occurs when a light wave passes by a corner or through an opening. Diffraction plays a paramount role in limiting the resolving power of any lens.

Doublet

Doublet is a lens design comprised of two elements grouped together. Sometimes the two elements are cemented together, and other times they are separated by an air gap. Examples of this type of lens include achromatic close-up lenses.

Dynamic range

Dynamic range is the maximum range of tones, from darkest shadows to brightest highlights, that can be produced by a device or perceived in an image. Also called tonal range.

Resolving power

Resolving power is the ability of a lens, photographic emulsion or imaging sensor to distinguish fine detail. Resolving power is expressed in terms of lines per millimeter that are distinctly recorded in the final image.

Vignetting

Vignetting is the darkening of the corners of an image relative to the center of the image. There are three types of vignetting: optical, mechanical, and natural vignetting.

Optical vignetting is caused by the physical dimensions of a multi-element lens. Rear elements are shaded by elements in front of them, which reduces the effective lens opening for off-axis incident light. The result is a gradual decrease of the light intensity towards the image periphery. Optical vignetting is sensitive to the aperture and can be completely cured by stopping down the lens. Two or three stops are usually sufficient.

Mechanical vignetting occurs when light beams are partially blocked by external objects such as thick or stacked filters, secondary lenses, and improper lens hoods.

Natural vignetting (also known as natural illumination falloff) is not due to the blocking of light rays. The falloff is approximated by the "cosine fourth" law of illumination falloff. Wide-angle rangefinder designs are particularly prone to natural vignetting. Stopping down the lens cannot cure it.

Flare

Bright shapes or lack of contrast caused when light is scattered by the surface of the lens or reflected off the interior surfaces of the lens barrel. This is most often seen when the lens is pointed toward the sun or another bright light source. Flare can be minimized by using anti-reflection coatings, light baffles, or a lens hood.

Ghosting

Glowing patches of light that appear in a photograph due to lens flare.

Retrofocus design

Design with negative lens group(s) positioned in front of the diaphragm and positive lens group(s) positioned at the rear of the diaphragm. This provides a short focal length with a long back focus or lens-to-film distance, allowing for movement of the reflex mirror in SLR cameras. Sometimes called an inverted telephoto lens.

Anastigmat

A photographic lens completely corrected for the three main optical aberrations: spherical aberration, coma, and astigmatism.

By the mid-20th century, the vast majority of lenses were close to being anastigmatic, so most manufacturers stopped including this characteristic in lens names and/or descriptions and focused on advertising other features (anti-reflection coating, for example).

Rectilinear design

Design that does not introduce significant distortion, especially ultra-wide angle lenses that preserve straight lines and do not curve them (unlike a fisheye lens, for instance).

Focus shift

A change in the position of the plane of optimal focus, generally due to a change in focal length when using a zoom lens, and in some lenses, with a change in aperture.

Transmittance

The amount of light that passes through a lens without being either absorbed by the glass or being reflected by glass/air surfaces.

Modulation Transfer Function (MTF)

When optical designers attempt to compare the performance of optical systems, a commonly used measure is the modulation transfer function (MTF).

The components of MTF are:

The MTF of a lens is a measurement of its ability to transfer contrast at a particular resolution from the object to the image. In other words, MTF is a way to incorporate resolution and contrast into a single specification.

Knowing the MTF curves of each photographic lens and camera sensor within a system allows a designer to make the appropriate selection when optimizing for a particular resolution.

Veiling glare

Lens flare that causes loss of contrast over part or all of the image.

Anti-reflection coating

When light enters or exits an uncoated lens approximately 5% of the light is reflected back at each lens-air boundary due to the difference in refractive index. This reflected light causes flare and ghosting, which results in deterioration of image quality. To counter this, a vapor-deposited coating that reduces light reflection is applied to the lens surface. Early coatings consisted of a single thin film with the correct refractive index differences to cancel out reflections. Multi-layer coatings, introduced in the early 1970s, are made up of several such films.

Benefits of anti-reflection coating:

Circular fisheye

Produces a 180° angle of view in all directions (horizontal, vertical and diagonal).

The image circle of the lens is inscribed in the image frame.

Diagonal (full-frame) fisheye

Covers the entire image frame. For this reason diagonal fisheye lenses are often called full-frame fisheyes.

Extension ring

Extension rings can be used singly or in combination to vary the reproduction ratio of lenses. They are mounted between the camera body and the lens. As a rule, the effect becomes stronger the shorter the focal length of the lens in use, and the longer the focal length of the extension ring.

View camera

A large-format camera with a ground-glass viewfinder at the image plane for viewing and focusing. The photographer must stick his head under a cloth hood in order to see the image projected on the ground glass. Because of their 4x5-inch (or larger) negatives, these cameras can produce extremely high-quality results. View cameras also usually support movements.

135 cartridge-loaded film

43.27 24 36
  • Introduced: 1934
  • Frame size: 36 × 24mm
  • Aspect ratio: 3:2
  • Diagonal: 43.27mm
  • Area: 864mm2
  • Double perforated
  • 8 perforations per frame

120 roll film

71.22 44 56
  • Introduced: 1901
  • Frame size: 56 × 44mm
  • Aspect ratio: 11:14
  • Diagonal: 71.22mm
  • Area: 2464mm2
  • Unperforated

120 roll film

79.2 56 56
  • Introduced: 1901
  • Frame size: 56 × 56mm
  • Aspect ratio: 1:1
  • Diagonal: 79.2mm
  • Area: 3136mm2
  • Unperforated

120 roll film

89.64 56 70
  • Introduced: 1901
  • Frame size: 70 × 56mm
  • Aspect ratio: 5:4
  • Diagonal: 89.64mm
  • Area: 3920mm2
  • Unperforated

220 roll film

71.22 44 56
  • Introduced: 1965
  • Frame size: 56 × 44mm
  • Aspect ratio: 11:14
  • Diagonal: 71.22mm
  • Area: 2464mm2
  • Unperforated
  • Double the length of 120 roll film

220 roll film

79.2 56 56
  • Introduced: 1965
  • Frame size: 56 × 56mm
  • Aspect ratio: 1:1
  • Diagonal: 79.2mm
  • Area: 3136mm2
  • Unperforated
  • Double the length of 120 roll film

220 roll film

89.64 56 70
  • Introduced: 1965
  • Frame size: 70 × 56mm
  • Aspect ratio: 5:4
  • Diagonal: 89.64mm
  • Area: 3920mm2
  • Unperforated
  • Double the length of 120 roll film

Shutter speed ring with "F" setting

The "F" setting disengages the leaf shutter and is set when using only the focal plane shutter in the camera body.

Catch for disengaging cross-coupling

The shutter and diaphragm settings are cross-coupled so that the diaphragm opens to a corresponding degree when faster shutter speeds are selected. The cross-coupling can be disengaged at the press of a catch.

Cross-coupling button

With the cross-coupling button depressed speed/aperture combinations can be altered without changing the Exposure Value setting.

M & X sync

The shutter is fully synchronized for M- and X-settings so that you can work with flash at all shutter speeds.

In M-sync, the shutter closes the flash-firing circuit slightly before it is fully open to catch the flash at maximum intensity. The M-setting is used for Class M flash bulbs.

In X-sync, the flash takes place when the shutter is fully opened. The X-setting is used for electronic flash.

X sync

The shutter is fully synchronized for X-setting so that you can work with flash at all shutter speeds.

In X-sync, the flash takes place when the shutter is fully opened. The X-setting is used for electronic flash.

1 - 1/500 + B

1 second - the slowest available shutter speed.

1/500th of a second - the fastest available shutter speed.

B (Bulb) - a setting in which the shutter stays open as long as the release button remains depressed.

MF

Sorry, no additional information is available.

Unable to follow the link

You are already on the page dedicated to this lens.

Cannot perform comparison

Cannot compare the lens to itself.

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.

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, Leica, Nikon, Pentax, Sony etc.) are always incompatible. In addition to the mechanical and electrical interface variations, the flange focal distance (distance from the mechanical rear end surface of the lens mount to the focal plane) is also different.

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. Magnification is expressed as a ratio. 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".

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 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 lens element 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.