What are common photo techniques

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As in many areas of technology, there is also an abundant use of technical terms in modern photography, some of which have a real optical, physical or technical basis or origin, but often only owe their birth to the marketing departments of large manufacturers.

I have collected and sorted a number of common and important terms and will try to keep this overview up to date. Of course, it cannot replace the content of a lexicon or an encyclopedia and should not be understood as a WiKi.

 

A - D...E - H...IN... O - Q...R - T...U - Z

 

Adobe RGB color space

Adobe RGB an extended RGB color space that is recommended for images that are to be transferred to the CMYK color space for further processing and printing.

AF auxiliary light

Many autofocus systems have problems setting the focus satisfactorily in poor lighting conditions. Therefore, some cameras can send out their own light signal as support if necessary. In this case, the AF auxiliary light (auto focus auxiliary light) sends a bundled beam of light onto the subject in order to provide the autofocus with additional light for assessing the correct focus.

Aliasing

Aliasing is an image error that can arise during digital recording in the camera or further processing in an image processing program. The aliasing effect can be seen, among other things, in sloping lines that look like a staircase or a sawtooth, although in the original it appears as a smooth line.

Anti-aliasing filter

In order to avoid or at least largely reduce aliasing effects, many manufacturers of photo or video cameras place special low-pass filters in front of the image sensor in order to filter out the high frequencies of the image. Such low-pass filters work in such a way that light that hits a pixel is scattered onto the directly neighboring pixels. As a side effect, however, the anti-aliasing filters reduce the achievable image sharpness.

APS-C format

APS-C as the original film format of 25.1x16.7mm is now often specified as the size format for image sensors in digital single-lens reflex cameras.

resolution

The resolution of digital cameras is mainly influenced by the quality of the lens, the number and size of the pixels in the sensor and the type of image processing performed by the camera.

Shutter release delay

In principle, the release process when photographing with a digital camera can be divided into three phases: focusing, determining the coating parameters and the actual exposure process of the sensor. With many compact cameras, the first two phases take a very long time and lead to an often annoying shutter release delay between tapping the shutter release and the actual exposure, while these phases are much faster in a DSLR and are hardly worth mentioning.

Autofocus

Autofocus (AF) refers to the technology and process of an optical unit, such as a lens or camera, for automatically focusing a subject or object.

Artifacts

With JPEG compression, the image is divided into blocks of 8 x 8 pixels. With extremely strong compression, these square blocks of pixels can become visible, and this is called JPEG artifacts.

bayonet

Some cameras, especially single-lens reflex cameras, are equipped with a quick release, a so-called bayonet connection, which allows lenses to be changed quickly. However, there are various manufacturers' standards that rarely allow the lenses to be used in a compatible manner with one another.

Exposure time

The exposure time of a photo camera defines the length of time a photosensitive medium, be it a film in analog photography or the CCD / CMOS chip of a digital camera, is exposed to light to record an image.

Automatic exposure

Automatic exposure controls control the aperture and / or shutter automatically based on the values ​​determined by the camera's internal exposure meter. Automatics that either only control the shutter or aperture are often referred to as semi-automatic, while fully automatic controls control the aperture and shutter.

Light meter

A camera's exposure meter measures the light reflected from the object. This is used as the basis for controlling the automatic exposure. Since the parameters determined naturally depend on the object's properties and its reflectivity and most light meters assume an average reflectance of 18%, the results can be falsified e.g. in snowy landscapes, on bright beaches, etc.

Image stabilizer

Image stabilizers are used to reduce "blurring", which can happen very quickly, for example when taking photos with the hand with telephoto lenses. However, they cannot help with normal movement blurring. Image stabilizers can either be part of the lens (e.g. movable lens element in connection with a gyrodetector) or the camera, in which the recording sensor is supported and adjusted accordingly.

Flashlight

In photo technology, a flash light is understood to be a lighting device that provides the necessary illumination of the subject or object at the moment the photo is taken by means of a flash of light. The flash of a flash unit usually only lasts a few microseconds and therefore synchronization with the shutter speed of the camera is not a problem. Important parameters of a flash unit are the guide number LZ and the color temperature. There are many different technical versions of a flash unit, but in principle a distinction can be made between flash units that are internal to the camera and flash units to be connected externally.

Bluetooth

Bluetooth is a radio interface with which, in addition to cell phones or notebooks, some digital cameras are also equipped. The range of this interface is about 10 m in version 2.0.

Image noise

Electronic image sensors, as used in digital photo cameras or camcorders, have inherent noise that mainly consists of dark noise (noise even without lighting), shot noise (photon noise) and readout noise (noise from the amplifier or readout electronics). These noise components are largely dependent on the technology and size of the recording sensor, the quality of the electronics and also on the ambient temperature. Some of the noise components can be greatly reduced by suitable signal processing, which is now standard, especially in high-quality cameras.

Image sensor

The term image sensor has a broad meaning, and in digital photo technology it stands for the recording sensor that records the image in two dimensions instead of the film. In practice, this is done by a CCD or CMOS chip. As a reference point for the theoretically achievable resolution of a digital camera, the image points of the sensor are given in megapixels.

cover

The aperture regulates the incidence of light through the lens. The larger the f-number, the less light can pass through the lens. In conjunction with the exposure time parameter, the real exposure of the image sensor or the film can be controlled. At the same time, the aperture changes the depth of field. With an increased f-number, the depth of field also increases, which offers the experienced photographer scope for emphasizing the image between the actual subject and the background.

Shutter priority

If the exposure time of a camera is preselected manually and the aperture is automatically adjusted by the camera to the exposure conditions, this is known as automatic aperture control.

Glare protection

Modern digital cameras often no longer have an optical viewfinder, so that one is completely dependent on the control monitor. But as soon as you take pictures under very bright conditions, such as on the beach in sunlight, the motifs can hardly be seen on this monitor. This can be remedied by a monitor anti-glare protection, which severely restricts the lateral radiation of light on the monitor and thus makes the image easier to assess.

Blooming

The pixels of a digital sensor can only hold a limited amount of charge. If the incident light is above the amount of the storable charge, the resulting charge carriers overflow into neighboring pixels. This manifests itself in "blooming" spots or strokes in such overexposed image areas. In order to reduce the blooming effect or to prevent it entirely, the manufacturers of modern digital cameras use sensors with anti-blooming gates (ABG), which have a kind of barrier or space for the excess charge to "run off" between the individual pixels.

Candela

Candela (cd) is the basic unit for luminous intensity. In contrast to the luminous flux, which is measured in lumens (Im) and describes the entire integral light emission of a light source, the luminous intensity indicates the emission of the light in a certain direction.

DPI

DPI, written out Dots per inch refers to the number of pixels per inch (inch, 2.54 cm). This unit of measurement for resolution is mainly used when printing images and text. The more pixels there are within an inch, the better the print quality should be, provided that other parameters do not negatively affect it.