Camera

Under a camera (short for photographic apparatus, in the technical sense still camera, camera, camera obscura, Latin for "dark chamber " ) refers to a device for receiving and storing a single image (Nursing) or a short series of frames. Also the terms clippers and photo Colloquially used in German. In contrast, there are motion picture cameras, so film cameras, video cameras and digital cinema cameras, whose primary purpose is to detention of continuous image sequences.

The camera that stores images on a film, was ousted in most areas, especially in the consumer sector, of digital technology.

The derived from the English term camera cam short form is used in abbreviating words art, such as webcam, digicam or Screencam ( for digital camera).

In particular, in the field of digital cameras and digital camcorders, the transitions are fluid; some camera models also dominate the record short movies and most camcorders support frame recording.

Construction

A camera as an imaging system has a combination of lens and aperture, whose distance can be changed for the film. The lens is a system of lenses, which acts as a convex lens as a whole. By combining different lenses (some from different types of glass ) are chromatic aberrations and distortion - especially at the edges - avoided.

Two parameters are essential for the lens:

• The focal length f of the lens, which determines the opening angle of the recording.
• The light intensity L of the lens. They are - to put it bluntly - how much light the lens can be fully open iris on the film. A typical specification for the light intensity L = d / f ( d: diameter of the front lens of the objective ), for example, L = 1: 2.0. For a lens with f = 60 mm, this means that the input lens having a diameter of 30 mm. When the light intensity 1: 4, the input lens would have only 15 mm in diameter. It is therefore less light into the lens, the arrangement is less sensitive, but usually cheaper.
• Thus, the film is right for him " amount of light " gets in the recording, you can influence this in two ways: Through the iris diaphragm, usually implemented as a circular aperture having a variable opening, limits the quantity of light.
• Due to the closure. He releases the light path for exposing the film for a certain configurable time. The times vary from a few milliseconds to a few seconds.

With SLR cameras before and after recording the light that strikes through the lens, deflected by a mirror and a prism to the viewfinder. This has the advantage that you can see almost exactly in the viewfinder the picture ( field of view), which can be seen in the image on the film.

In rangefinder cameras viewfinder and lens are decoupled. Especially in close-ups, it may happen that the to be seen in the viewfinder display window does not exactly matches that of what is seen later in the film. This disadvantage is compensated by the possibility of a very compact design part.

History and Development

Namesake for the entire genre of cameras is the camera obscura " dark chamber." This did not yet have the chemical film for image recording and initially also only have a small hole instead of a lens. She projected her image on a surface ( for example, in a walk-in box, that is a huge hole camera ), a screen or tabletop and served the production of realistic drawings.

The herein described technical development of the camera went along with the history of photography. In the first cameras that were designed for photography, it was Camerae obscurae of wood; they were made, inter alia, by the developments of Louis Daguerre ( daguerreotype ) of its brother- Giroux and previously in 1839 by the company Susse Frères in series, but also from various opticians as individual pieces.

Historically, The development of the photographic apparatus from the knowledge of the special case of parallelism of film (F), lens (O) and, accordingly, focal plane ( S), which is still regarded as a normal camera. The flexible camera design (eg, bellows ) first served only the distance setting.

The first all-metal camera turned Voigtländer 1841; still constructed in 1839 Carl August von Steinheil, the first calculated according to physical principles lens. This was in 1840 improved by Joseph Petzval, who designed the Petzvalobjektiv; while it was the first fast lens at all: It had a light intensity of 1:3,7, ie 16 times brighter than the lens of Daguerre's camera.

As the founder of the production of cameras in Germany applies Friedrich Wilhelm Enzmann, who campaigned in 1839 at Dresdner Anzeiger for its products.

Operation

A camera consists of three basic components: a lens focuses light and projects it onto an image plane; in this device is usually a lens, however, only a small opening in the front of the camera body is in hole cameras. A mechanical or electronic shutter controls the duration of the exposure of the recording medium. The aperture controls the light intake.

General Camera

Beyond a concrete construction of the works ' general camera " (abbreviated AF) as follows:

Three levels form the basic system of the general photographic apparatus (F ) film (O ) lens and the (S ) sharpness level. The two camera planes F and O are light-tightly in the AF and rotatably and slidably coupled.

Under the requirement that parallels at infinity meet ( projective geometry), always have all three a common intersection point (or a line of intersection ) in space, which is determined by the positions of F and O and - depending on the inclination angle to each other - more or less far away from the AF is.

The plane S arises in this intersection FO and runs over the in-focus point of the lens to the lens axis ( not perpendicular to the plane of focus S).

If the intersection of the two camera planes of the camera ( AF) infinitely far away, then enters the special case that all three levels aligns ( current and historical " normal camera " ) parallel to each other.

To make the AF mechanically practical, it requires the ability to F and O be adjusted so that from the point of intersection of the two camera planes, a line is generated similar to a hinge ( by common horizontal or vertical orientation of the camera standards, for example, in which film and lens plane are suspended ). After this initial setting, the levels can display the other setting again meet at only one point instead of a line (if both standards are twisted in opposite directions - for example, a vertical and a horizontal).

The sharpness level S is obtained by exact projection of a point in the scene through the lens to a point in the film plane. From the lens of view arises in the camera, a radiation beam, the tip of which meets with the film.

In practice, this results in a sharpness body; that is the focus range. When are ends of the beam cone just before or behind the plane of the film on it blur circles (Z ), which are featured by the eye up to a certain size accepted still as sharp and therefore appear more sharp.

With the arranged in the lens iris that controls the passage of the light through the lens, the size of the blur circle is determined: the smaller aperture produces radiation cone with smaller radii and acute angles that fall on the film, and therefore smaller blur circles, the corresponding appear sharper.

The focus in the AF body is a wedge; it starts on the focal plane (!) only at a distance of camera extract ( distance F to O) parallel to the film plane ( under the lens ). In wedge sharpness extends to infinity. In the special case - F and O are parallel - gives you the focus range Focus as a cuboid rather than a wedge ( because technically limited by the AF).

The sharpness of the wedge is in his section (side view) by its first zero ( in sketch: under the lens ), the near point N 2 and 3 the farthest point F defined on the sharpness of the lens axis; N and F arise in this case from the nominal distance setting of the focus level S and the specific focal length of the lens. N and F ( near and far point of sharpness) also arise from the knowledge of the lens and the centrally located almost exactly between them focal plane S; N and F can therefore be determined by calculations (such as through the interactive table of Striewisch / Kluge, see below ).

With the values ​​for N, S and F, the distance from the zero point to the lens axis ( D) and the standardized variable Z ( circle of confusion each film format ) The key is to calculate ( get to N, S, F, for example, from Striewisch / Kluge = Interactive depth of field calculator ( version of 16 November 2007 on the Internet Archive ); Z for small format cameras 0.03 mm, for medium format cameras about 6 × 7 cm 0.05 mm for large format cameras 9 × 12 cm 0.09 mm to 0.1 mm or more per picture or recording format).

If the Sharpness wedge designed in two halves, even the part before and once the part behind the focal plane, is small divergent angle can result. As an approximation, the angle of the wedge in front of the focal plane, the nearest point to focus:

Here, D = distance of the lens axis to wedge the beginning; S = Sharpness setting on the lens axis; A = camera extension; N = near point of the specific focal length of the lens axis.

Simplified, this angle may be doubled for all the sharpness wedge.

The distance on the lens axis from the nearest point of the focus area to the focal point is about as great as that of the focal plane to the far point, the ratios change with each longer set distance at a very dense distance setting on camera - the distance between the focal plane to the farthest point then grows continuously compared with the distance to the nearest point.

Lenses are lens systems that are equipped with an orifice (and often a lock) combined. From the same location, on the same optical axis they draw all the same picture from your subject, so draw out equal areas and angles at different image sections - like the zoom lens, in which various focal lengths are fluidly connected with each other.

Normal lenses have about the screen size as focal length. Lenses with further viewing angle (wide angle lens) draw more off the subject smaller. Lenses with a smaller viewing angle ( distance lens ) are distinguished less by the subject larger. Accordingly, the circles of confusion are magnified in the latter and the focus range is small (especially small for macro shots ).

Remote lenses - with a low viewing angle - telephoto lenses differ from the fact that the latter within the lens system a magnification system (Tele - converter) and therefore included in its overall length is shorter than its focal length.

In the infinity (∞ ) of an - in moving its levels - AF is nominally the distance from O to F is equal to the focal length. This Anlagemaß from F to O is shorter and in some wide angles around longer than the focal length with telephoto lenses. For calculations, for example, the image scale, the nominal focal lengths apply.

Denser distances into focus the subject than infinity requires longer excerpts of the camera ( for the 1:1 scale is needed twice the focal length).

When shooting the subject with the same scale can be up to 1:1 picture size m in practice approximated with all lenses at the same aperture ( and the same image format) are assumed as clear areas; at larger scales in the macro range into does not apply anymore. Are to be considered may still normalized blur circles for the various image formats ( Z), resulting in different screens for different formats. With different formats, different image formats result.

Designs

Cameras can be distinguished by a number of criteria, such as the recording format, an optical system, used film type or application. Due to the different classification criteria, a camera can appear simultaneously in several categories, for example, a camera viewfinder at the same time be a small image and a bellows camera. Be divided cameras especially ...

A) according to the recording format

• Large-format or large format cameras (formats from 6x9 cm on sheet film, historically also on glass plates)
• Medium format cameras (formats 4,5 x6, 6x6, 6x7 and 6x9 cm on roll film )
• Film Cameras ( 24x36 mm on small -screen and 35 - mm film, but also Instamaticfilm )
• Half-format cameras (format 18x24 mm also on miniature film )
• Smallest format or miniature cameras

B) after the optical construction

• Viewfinder camera - equipped with a see-through viewfinder (often a compact camera )
• Viewfinder camera with distance measurement uncoupled rangefinder - the measured distance must be manually transferred to the taking lens
• Coupled rangefinder - setting parallel to the receiving lens, separate insight

• Single-lens reflex ( SLR = Single Lens Reflex) and
• Twin-lens reflex ( TLR Twin Lens Reflex = )

C ) to imaging

The image can be recorded on a film or an image sensor.

Film

• Roll film cameras ( for roll film )
• 35 mm cameras ( for small- or 35 - mm film )
• APS cameras ( APS film)
• Disc cameras ( for disc film )
• Pocket cameras ( for Pocket movie)
• Instamatic cameras ( for Instamatic cartridges)
• Polaroid Camera ( for instant film )

Image sensor

• Digital camera with CCD image sensor
• Active pixel sensor
• Vidicon tube
• Iconoscope
• Nipkow disk
• Microbolometer
• Pyroelectric array

For camera systems of larger sizes ( roll film cameras and professional cameras ) existed Polaroid backs, today are corresponding digital modules available as so-called Digibacks.

Based on the recording medium is also a distinction between cameras with chemical recording media (" analog camera " with photographic film and instant print film camera ) as well as electronic recording media (digital camera, still video camera). If a camera is able to adjust with an active or passive process, the focus itself, it is called an auto-focus camera. In all cases, the camera can be configured as a single-lens reflex viewfinder or camera.

There are also several special cameras for specific technical domains, such as high-speed cameras, measuring cameras, panoramic cameras, stereo cameras, Topographic cameras, surveillance cameras, underwater cameras, thermal imaging / infrared cameras / infrared cameras and two-room cameras. Another special type of photographic camera is the AstroCam. It consists of a model rocket with a pocket camera in the tip and allows the taking of aerial photographs.

Historical cameras

Even vintage cameras can be on the recording format, divide and rename optical design or film type. In addition, however, other historical terms have naturalized:

Cameras with certain structural properties

• Balgenkamera
• Folding camera folding camera
• Box Camera
• Sliding box camera
• Color camera
• Standards camera
• Clockwork camera
• Change magazine camera, etc.

Historical Special cameras:

• Handheld
• Press camera
• Secret camera
• Paperback book camera and camera
• Miniature camera
• Snapshot camera
• Vest pocket camera, etc.

Furthermore, film cameras can be distinguished ( with roll film ) and plate cameras with wet or dry plates and possibly with cassette (Tray camera).