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Alpa Reflex 6c

35mm MF film SLR camera • Collectible

Specification

Production details:
Announced:1960
Production type:Small-batch production
System:● Alpa (1952)
Format:
Maximum format:35mm full frame
Film type:135 cartridge-loaded film
Mount and Flange focal distance:Alpa [37.8mm]
Shutter:
Type:Focal-plane
Model:Mechanical
Speeds:1 - 1/1000 + B
Exposure:
Exposure metering:Through the separate window
Exposure modes:Manual
Physical characteristics:
Weight:680g
Dimensions:146x95.3x50.8mm

Manufacturer description #1

LIGHTNING REFLEX AND HAIR-TRIGGER RELEASE END ALL IMAGE BLACK-OUT

The NEW ALPA 6c ALL-IN-ONE 35 mm camera

With "six gun" or 35 mm camera - split-second reflex control still remains the "mark of the master".

The new ALPA 6c with Lightning Reflex Mirror and Hair-trigger Release gives you this complete image control - automatically. Your lifesize groundglass with built-in rangefinder gives you absolutely accurate framing, focusing and depth-of-field control, without black-out.

Manufacturer description #2

ALPA introduces the NEW version of their model 6

Now you have the option of straight 0° viewing or convenient 45° viewing (an ALPA exclusive)...

The COMPACT, LIGHTWEIGHT, STREAMLINED ALPA 6c with built-in exposure meter!

... available in chrome or deep satiny black finish.

The ALPA formula:

Swiss chronometer precision + custom ground optics = unconditional guarantee for highest mechanical and optical performance.

Which do you prefer?...

New: Rapid, straight 0° Viewing, the traditional way, with the ALPA 6c

or

Convenient 45° Viewing, the natural angle for reading, with the other ALPA models. Allowing a completely relaxed position of the head without nose interference, it is the ideal camera for wearers of glasses, low angle shots, close-up and copy work, photomicrography, and overhead shots.

  1. The ALPA is a triumph of Swiss precision: Each ALPA is as painstakingly assembled as a fine Swiss watch, literally custombuilt to your order with all the skill and experience of the Swiss watchmakers.
  2. Ultrafine groundglass gives a strikingly brilliant, 1:1 lifesize image of exactly 23x35 mm, i.e. 1/2 mm less on each side than 24x36 mm frame, a margin covered by the 2x2 slide mounts.
  3. New: Built-in exposure meter in ALPA 6c, for direct readings of exposure time and diaphragm or Optical Viewfinder or combined Multifocal Viewfinder/separate Rangefinder (ALPA 8) in all other ALPA models. Metraphot exposure meter can be attached to accessory clip, fits into eveready case.
  4. New: film reminder dial of ALPA 6c indicates black and white, color negative, color positive (reversal) indoor or outdoor film.
  5. Vibration-free shutter, controlled by Swiss precision movement, offers M, F and X-synchronization (up to 1/64), selftimer (1-20 seconds), electronically tested speeds from 1/1000 to 1 second and B, plus intermediate speeds between calibrations: 60 different settings!
  6. Frontal rapid wind lever (optional), for fast film transport without removing camera from eye. Model 6c is always furnished with lever.
  7. New: unique pull-out rapid rewind crank, for highspeed rewinding.
  8. New: Release button returns exposure counter automatically to zero.
  9. New: Recessed eyelets accept roundshaped, braided leather neckstrap.
  10. The only complete set of 10 lenses with Automatic Diaphragm: 24 mm - 28 mm - 35 mm - 50 mm - Macro-Switar 50 mm - 90 mm - 100 mm - 135 mm - 150 mm - 180 mm! Other lenses range up to 500 mm Super-Telephoto.
  11. Automatic diaphragms close and open automatically, work with bellows and extension tubes (twin cable release), can be disconnected for checking depth-of-field or use of selftimer.
  12. 35 mm f 2.8, Macro-Switar 50 mm f 1.8 and 135 mm f 3.5 lenses have Automatic depth-of-field indicators.
  13. ALPA APOCHROMATS: Switar and Macro-Switar 50 mm f 1.8, Kinoptik 100 mm f 2 and 150 mm f 2.8 highspeed APOCHROMATS offer exclusive correction of all primary colors, for lifelike color rendition.
  14. ALPA ALL-IN-ONE lenses: Macro-Switar 50 mm f 1.8 APOCHROMAT focuses from infinity to 2", Makro-Kilar 40 mm f 2.8 from infinity to 4" or 2" and Makro-Kilar 90 mm f 2.8 from infinity to 5", without accessories! Reproduction ratios and exposure factors are calibrated on lensmount.
  15. ALPA Close-up and Micro-equipment: ALPA ALL-IN-ONE lenses, extension tubes, bellows, Luminar close-up lens and micro-adapter offer continuous focusing range from infinity all the way down to ultra close-ups of 1:1 - 10:1 and (with microscopes) up to 1500:1 magnification, without gap.
  16. Quickchange, patented ALPA bayonet lensmount guarantees snug fit, is never too loose, never too tight.
  17. 100% Lens Consistency: Each ALPA lens is hand-picked for you, by taking test shots of a huge lens chart, scrupulously inspecting resolving power, contrast and overall illumination, carries an unconditional guarantee for highest optical performance.
  18. ALPA's limited production is strictly geared to the most rigid Quality standards: Exceptionally sturdy construction withstands the most rugged use, works under extremely warm and cold temperatures (down to 20° below zero!), reduces repairs to an absolute minimum: less than 5%!
  19. More than 40% (forty percent) of the ALPA plant is engaged in Control and Inspection.
  20. New: Compact, lightweight, elegant, ultra modern design.
  21. New: Streamlined for utmost simplicity and speed of operation, yet so complete and ultra versatile, the ALPA 6c is the ideal camera for all your photographic needs.

The ALPA ALL-IN-ONE 35 mm Camera combines all the distinct features of the three most advanced camera types...

  1. It's a Single-lens Reflex: Parallax-free viewing through the actual picture taking lens automatically gives you accurate framing, critical focusing and complete depth-of-field control - with any lens, at any distance, for any magnification.
  2. It has all the advantages of the Twin-lens Reflex: ALPA's lightning reflex mirror with hairtrigger release PLUS 10 lenses with Automatic Diaphragm (from 24 mm up to 180 mm!) offer continuous observation of the brilliant, reinverted ground-glass image, without blackout - with any lens, at any distance, for any magnification.
  3. And it's got a coupled Rangefinder*, without any limitations: Rangefinder with 45° split-image, clear circle built into ground-glass pinpoints focus instantly, automatically AND couples to any lens (24 mm up to 5000 mm), at any distance (from infinity down to ultra close-ups and photomicrography), for any magnification (1:10 - 1:1 - 10:1 - 1500:1).

You buy ONE ALPA and get THREE cameras: Single-lens Reflex, Twin-lens Reflex and Rangefinder Camera, combined in the ALPA ALL-IN-ONE 35 mm Camera.

* except models 4 and 5.

Manufacturer description #3

The ALPA 6c represents the result of years of research, development and quality controls in the manufacture of this Swiss precision camera to meet the ever increasing demands of the photographer. It accepts the same lenses and accessories as the previous models ALPA 4, 5, 6, 7, 8 and 4b, 5b, 6b, 7b and 8b, except for the everready case.

The ALPA 6c has a built-in prism. which offers you straight (0°) through-the-lens framing, focusing and depth-of-field control on the groundglass.

Operated by a hairtrigger release, the lightning reflex mirror of the ALPA flips up instantly for the exposure and returns into viewing position immediately thereafter. There is no noticeable image blackout, even if you keep the release button depressed.

Like the earlier models the ALPA 6c is made of a light-metal, which combines exceptionally light-weight with extreme sturdiness. The body is protected by a plastic material that is impervious to sweat, cold, heat and other climatic influences. The camera has been designed for utmost simplicity and speed of operation, with fingertip controls that are readily accessible. Important: Two earlier 50 mm standard lenses. which came in a retractable mount, the Alorar 50 mm f/3.5 and the Alfinon 50 mm f/2.8, should not be used with the ALPA 6c or the ALPA b models. Since the lightning reflex mirror of these cameras cannot be pushed back, it will be damaged, if these lenses are retracted.

Manufacturer description #4

The ALPA 6c supplied with its Kern Macro-Switar 50 mm f/1.8 lens, breaks effortlessly through the short distance barrier, enabling you to focus down to ... 7 inches from your subject! What a wealth of new possibilities this opens up for the close-up specialist, whether intent on his favourite insect, flower or rock formation, student of scientific or medical research or observing nature's rich canvas at close quarters and there finding many an artistic masterpiece to reward him.

Close-up photography, in which the Alpa has made advances undreamt of a few years ago, has risen above mere photographic technique to take its place as a new art form.

It is in artificial light or in very poor visibility that the combination of the two outstanding features of the Alpa - ultra-Iuminous reflex plus automatic preselective diaphragm - proves its true superiority. Even in a dark interior you can view your subject clearly and probe into the dimmest corners of your image.

The Alpa is an extremely fast camera both in taking and rewinding. The 6c model is fitted with a pull-out knob which acts as a crank for high speed rewinding. The frontal rapid wind lever, which automatically sets the shutter, winds on the film and operates the exposure counter, is an enormous advantage to the photographer wishing to take a serie of shots in rapid succession.

By means of a single button, the Alpa offers you a complete range of shutter speeds from one second to 1/1000th second, passing through 60 intermediate speeds, 11 of which are noted on the scale and 8 indicated by a mark. Time exposures can be taken by cable release. A built-in selftimer ranges up to 20 seconds.

The Alpa undergoes rigid tests both for its mechanical operation and photographic quality, that would be devastating to any other camera. Under the scrutiny of an electronic testing device, the shutter release must operate 600 consecutive times before being passed as perfect. Every Alpa lens is double-checked, first in the factory where it is made, then in the Alpa laboratories where it is given its final adjustments. Every lens therefore has a permanent "record" which is kept at the factory. Every Alpa receives an individual Certificate of Origin which your specialized Alpa dealer will be proud to sign and hand to you on the day that you become the fortunate owner of an Alpa camera.

But photography at close range is only one of the specialities of the "Swiss watchmakers' camera". The Alpa is equipped with a wide range of superb interchangeable lenses, nearly all of them with automatic preselective diaphragm. Moreover, all these Alpa lenses - there are 14 at present including 4 apochromats - are instantly interchangeable.

On the Alpa, precision reflex framing shows the exact area of a mounted slide, i.e. 23 x 35 mm. This is of the utmost importance both for colour transparencies and macrophotography.

This framing remains exact over the whole range of distances. The Alpa's groundglass gives you complete control of sharpness, depth of field and colour harmony.

The Alpa offers ultra-luminous reflex viewing - the only system that gives complete satisfaction in miniature colour photography. Furthermore, as the Alpa's lenses are fitted with automatic preselection, you are free to take full advantage of reflex viewing and compose the framing of your picture up to the very edges.

Focusing by means of the helical ramp of the lens guarantees continuous control of the image on the groundglass. Since the Alpa's split-image rangefinder is in the centre of the groundglass itself, focusing could not be easier. The rangefinder is in diagonal section so that focusing can be done equally easy either on horizontal or vertical lines, with complete accuracy. The central rangefinder is surrounded by a clear zone (a virtual optical window) for checking the aerial image.

The reflex mirror has a lightning return and disappears only for the moment of exposure then flips back instantly. This means that there is virtually no image black-out for any exposure faster than 1/30th second and the photographer can thus keep his subject under constant observation after exposure as well as beforehand.

Manufacturer description #5

Model 6c introduced an asymmetric form of the prism head covering, combined with a new selenium exposure meter. Moreover, the shoulders of the upper part of the body that had hitherto been rounded were now redesigned to be angular. As a first for ALPA, there was also a horizontal viewing eyepiece - until then there had either been a waist-level viewfinder (ALPA Reflex) or a vertical (model 4), respectively a 45° viewing angle eyepiece (models Prisma Reflex, 5 and 6 - except for 6c - as well as 7 and 8).

From the Supplement to "The Alpa Camera" (1961)

Since the fall of 1960, another Alpa model, the 6c, has been available. It is immediately distinguishable from other Alpa models principally by two features: the straight, eye-level viewfinder in place of the characteristic Alpa 45-degree angle, and the built-in photoelectric exposure meter. Since many prospective Alpa photographers will still prefer the unique advantages of the inclined reading-position finder, previous Alpa models will continue to be offered.

Esthetically, the Alpa 6c has the appeal of elegance and streamlined body strength, handsomely modern and obviously dedicated purely to function. The Alpa 6c weighs only 1 1/2 pounds, which is a fairly light weight for a 35mm single-lens reflex in the top price bracket, and it measures a compact 5 3/4 x 3 3/4 x 2 inches.

The new viewfinder, which facilitates the use of the camera for vertical shots, as well as horizontals, shows an exceptionally fine ground-glass image of the subject in practically the lifesize ratio of one-to-one (the actual image size is in the ratio of 0.95:1). The optical rangefinder in the center of the ground glass has a diagonal split image, for focusing both on vertical and horizontal lines, and a clear circle. Just above the window of the built-in Metraphot meter are the light-indicating needle and the exposure dial.

The model 6c retains such other features of the Alpa camera as the hairtrigger instant reflex mirror release; dial-adjusted shutter speeds from 1 second to 1/1000th of a second, and intermediate settings, 60 in all; and adjustable self-timer for delays of 1 second to 20. Normally, the 6c is equipped with the 50mm f/1.8 Apochromat Switar (focusing to 17 inches) or the Macro-Switar, which focuses as close as 7 inches.

The Alpa 6c also is obtainable in the deep satin all-black finish sometimes preferred by the photojournalist for unobtrusive work, with scuffproof covering, either in black or dark green.

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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.

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, 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. 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 focus override in autofocus mode

Allows to perform final focusing manually after the camera has locked the focus automatically. Note that you don't have to switch camera and/or lens to manual focus mode.

Manual focus override in autofocus mode

Allows to perform final focusing manually after the camera has locked the focus automatically. Note that you don't have to switch camera and/or lens to manual focus mode.

Electronic manual focus override is performed in the following way: half-press the shutter button, wait until the camera has finished the autofocusing and then focus manually without releasing the shutter button using the focusing ring.

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/ 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.