I want to know some technical terms about photography.

Technical terms related to photography:

Disorder: disorder

A photographic lens can not completely restore a point or a light with mixed wavelength to a point, which is called aberration. The aberration of continuous spectrum is chromatic aberration; The aberration of single wavelength includes spherical aberration, comet aberration, astigmatism, image plane bending and distortion aberration. For example, taking a black spot becomes an image similar to a comet dragging its tail, which is called comet aberration.

automatic exposure

Automatic exposure is mainly divided into three categories: automatic program exposure, aperture pre-exposure and shutter pre-exposure.

AF-I Nikon lens

Lens series with built-in autofocus motor and CPU. The built-in chip on the lens will transmit the distance of the focused object back to the camera body as a reference for photometry, so it belongs to one of D-type AF nikkor lens.

AF-S ultrasonic motor lens

Nikon's new series of lenses, equipped with ultrasonic motors, also emphasize the advantages of mute, fast focus and full-time manual focus.

Ais Nikon lens

AIS is the abbreviation of automatic indexing shutter. At first, it was 1982, which was similar to the AI type. There is a semi-circular groove at the connecting ring, which can be controlled by the fuselage to the aperture value of the lens. Suitable for three exposure procedures, and can cooperate with most of Nikon's fuselage. It is the most compatible lens.

Aperture: aperture

In the interchangeable lens of a monocular camera, a plurality of blades are wound in a rainbow shape to adjust the aperture through which light enters. The lens should indicate the maximum aperture of the lens (series called F value), such as 55mm 1:2.8, the former means the focal length is 55mm, and the latter means the maximum aperture is f/2.8. The smaller the aperture number, the larger the aperture, for example, f/2 is one level larger than f/2.8 aperture (1.4 times is one level). F equals the focal length divided by the pupil diameter at the aperture entrance. The larger the maximum aperture, the larger the lens diameter and the more expensive it is.

Aperture priority ∴: Aperture prerequisite

The photographer adjusts the aperture value, and then the camera automatically measures the light to determine the shutter value; Aperture exposure is more suitable for determining the depth of field (such as landscape photography and portrait photography); Because the smaller the aperture, the longer the depth of field.

Aperture ratio: aperture ratio.

The effective aperture of a lens divided by the focal length is called aperture ratio. For example, 50mm f/ 1.8 is 1: 1.8, which is exactly the reciprocal of f value.

APO lens

Sigmapo lens adopts ultra-low dispersion lens to correct dispersion phenomenon (light with different wavelengths cannot be focused on a plane after refraction) and improve image quality.

ASA:: American standard agreement

American Standards Institute, film sensitivity protocol, see ISO.

Aspheric mirror: Aspheric mirror

Aspherical mirrors are used to eliminate the aberration and glare of comets and try to correct the curvature and distortion of the image plane. Because the correction ability of one aspherical mirror is equal to that of multiple spherical lenses, the use of aspherical lenses in the lenses can achieve lightweight.

Bulb setting

Refers to long exposure, and some cameras are marked as T shutter.

Basic autofocus system

The abbreviation of Base-Stored Image Sensor is the focusing mechanism of most autofocus cameras.

Support: bracket exposure

Take three photos with equal exposure, such as less than one level, normal and more than one level, which is suitable for situations where complex light sources or cameras are difficult to measure light correctly.

CCI (color contribution index)

CCI refers to the standard film under a specific light source and protocol, and a lens shows the index of color change. Quantized as CCI coordinates, there are three axes, representing the three primary colors of red, blue and green respectively. 0/5/4 is set as the reference value, which defines the allowable range of CCI coordinates for lens manufacturers' reference. If it exceeds the allowable range, it means that the tone deviation of the lens is too large.

Center weighted average measurement: center focused measurement

The focus of photometry is the center, and the rest of the pictures are measured by average. More suitable for landscape photography. As for the central area, it varies from camera to camera, accounting for about 20-30% of the whole picture.

CMOS autofocus system

Canon EOS-3 and EOS 300 are equipped with a new self-aligning focusing system (component) complementary metal oxide semiconductor sensor, which emphasizes the advantages of faster reading speed of focusing data, higher pixels per unit area (which can increase the focus) and low power consumption. The problem in previous applications is that the improvement of pixels will affect the "signal-to-noise ratio" and make the low brightness noise too high.

Coating: coating

Coating is to coat a thin transparent film on the lens surface. The purpose is to reduce reflection, increase light transmittance, and suppress glare and ghost; Different colors of coatings also make the image color balance different. In addition, the coating can also delay the aging and discoloration of the lens.

C-pl: circular polarizer

Natural light vibrates evenly in all directions, and the polarizer only leaves a certain vibration direction for the passing light, so it can reduce the reflection of water and glass and make the sky bluer. Polarizers can be divided into linear polarizers and circular polarizers. The circular polarizer transmits light, and its vibration direction rotates in a spiral way, which is suitable for cameras with automatic focusing and metering.

Field curvature:: image surface curvature

A plane object can't really be imaged as a plane, but as a curved surface, that is, the image plane is curved. This phenomenon will blur the image quality around the picture, and reducing the aperture will not improve the curvature of the image surface.

Depth of field:

When the lens focuses on the subject, the objects within a certain distance before and after the subject will also become clear images. "Depth of field" is the distance range that is clear before and after. In the vernacular, we want a landscape photo with a longer depth of field, that is, we want the foreground and background to be as clear as possible. Aperture, lens focal length and the distance between the lens and the subject will all affect the depth of field. The smaller the aperture, the shorter the focal length of the lens, and the farther away from the subject, the longer the depth of field.

Depth of field preview:: Depth of field preview

If the camera can shrink the diaphragm blade before the shutter curtain is opened (when the film is unexposed), the depth can be previewed from the viewfinder window.

Distortion: distortion aberration

After a straight line is photographed by a lens, it becomes a bending phenomenon, which is called distorted aberration. Diagonal outward bending is "pillow shape" and inward bending is "barrel deformation". Zoom lenses are usually barrel-shaped at the wide-angle end and pillow-shaped at the telephoto end.

DX coding

The black and white grid on the film box is DX code, which can be read by the camera to represent the film speed (ISO value).

The goddess of dawn

Electronic optical system, Canon 135 monocular autofocus camera series. The first EOS camera is EOS 650 of 1987.

Electronic TTL

Through lens evaluation refers to Canon's advanced flash exposure system. The camera will decide the appropriate flash and camera exposure value according to the choice of focus, taking into account the field light, pre-flash reading, the calculation of focus, and even the brightness distribution and subject position of the picture.

EV: exposure value

Exposure value, the EV value is directly proportional to the shutter speed and inversely proportional to the aperture value. For example, if the aperture is f/4, the EV value of shutter1/60s is the same as that of aperture f/5.6 and shutter1/30s.

Telescopic tube: a telescopic tube used for close-up.

The telescopic tube lengthens the distance between the lens and the film, shortens the closest focusing distance of the lens and improves the macro magnification. The aperture value will not be changed, but the light will be weakened because of the lengthening of the lens, but the TTL metering system will not be affected. There is generally no lens in the extension tube, which has limited influence on image quality.

Eye-controlled focusing: eye-controlled focusing

Canon's unique eye-controlled focusing, using the infrared light-emitting diode on the eyepiece, enters the human eye, is reflected by the retina, and then returns to the camera through the SI lens, and is projected to the eye-controlled BASIS sensor, so that the camera can detect the position of the eye for eye-controlled focusing.

Spot: spotlight

Repeated refraction of the lens, reflection or scattering of the inner surface of the lens barrel, scattering of the inner surface of the camera, etc. Part of the film is affected by harmful light, which reduces the freshness and sharpness.

Floating system: floating focusing system

Generally speaking, the lens design has the best aberration correction at the commonly used focusing distance, but there may be kink aberration at the nearest shooting distance. The floating focus system can move a whole group of lenses according to the length of the lenses, which can improve the image quality of close-range description.

Fluorite: fluorite

The scientific name of fluorite is fluorite, unlike ordinary optical glass, which is made of silicon dioxide, barium fluoride and lanthanum at high temperature. Fluorite has the advantages of low tortuosity and low dispersion because of its unique crystal structure. When applied to lens design, it can achieve the benefits of improving the surrounding image and shortening the total length of the lens. In addition to natural fluorite, crystals (fluoride calcifications) can also be cultured artificially, but the cost is very high.

Ffplash: high-speed flash

Also known as high-speed synchronization, flash can cooperate at a higher synchronization speed than ordinary flash, even at the highest shutter speed of the camera. However, the flash index will weaken with the increase of shutter speed.

Focal length: focal length

When the focus is at infinity, the distance from the main point on the back of the lens to the film plane.

Focus: focus

A beam of parallel light will be imaged as a point at a certain distance after passing through a convex lens. This converging point is called the focal point.

Focus preset: focus preset

Set the focus lock on the subject at a certain distance in advance, and then do other shooting work; When the subject suddenly appears at the preset point, the lens can be quickly driven to focus by memory, which is suitable for shooting in sports fields.

Full-time MF: full-time manual focusing

When autofocusing, you can also adjust the final focus yourself, which is "full-time manual focusing". There are two types: "electronic manual focusing"-it is installed on the large-caliber telescope head, and the electronic circuit detects the rotation of the manual focusing ring and then drives the mirror motor; "Full-time mechanical manual focusing"-it does not need power consumption when it is turned on, but drives the lens group through a wheel and a rotating ring different from those in AF.

Ghost image:: Ghost image

When sunlight or a point light source enters the lens, after many reflections, a clear bright spot is formed at the relative position of the light source, just like a ghost, which is called a ghost. A ghost is a kind of light.

Gn: flash index

Derivative, when using 100 degree film, the GN value divided by the aperture value is equal to the correct exposure distance of the flash (in meters or feet).

HSM ultrasonic motor

The lens developed by Sigma Hypersonic Engine Company has built-in ultrasonic engine.

Hyperfocal distance: hyperfocal distance distance

Focusing on a certain point in the distance makes the other extreme of depth of field just infinite, and the shortest photographing distance from infinity to depth of field is called "hyperfocal distance distance". If the focus is set to hyperfocal distance distance first, it will fall within the depth of field from half of hyperfocal distance distance to infinity.

ISO∶: sensitivity

Iso (International Organization for Standardization) international standard agreement: film sensitivity to light; Low sensitivity refers to films below ISO 50, medium sensitivity refers to ISO 100~200, and high sensitivity refers to ISO 400 or above.

Image Stabilizer: Anti-vibration Mechanism

IS can slow down the speed of the security shutter by two levels (four times the time). When focusing is activated, the correction optical system is awakened at the same time. Gyroscope sensor will detect the direction and speed of lens vibration and send it to microcomputer. The microcomputer calculates the amount to be corrected and sends a signal to the movable coil to make the correction optical lens group move in parallel. The microcomputer will compare the amount of lens vibration with the correction amount, and then adjust it quickly to keep the image stable.

Internal focus: internal focus

In order to cope with the high zoom lens, reduce the weight and keep the lens length unchanged, the lens is divided into even groups instead of the whole group when focusing, and only the middle lens group is moved to focus, which is called internal focusing.

Mirror lock: The mirror is locked.

Before the shutter curtain is opened, the reflector will jump up and let the light enter the film (two actions are completed in succession); But for cameras with mirror lock function, you can jump first and then press the shutter (the two actions are separate). Its purpose is to prevent the mirror from bouncing up instantly when it vibrates, resulting in slight blurring of the image.

Modeling light:: modeling flash (finishing: sum of wind)

Modeling flash means that the flash flashes continuously for several seconds for photographers to preview the flash effect. Generally, high-end electronic flashlights have this function. When using modeling flash, pay attention to its high power consumption and prepare more batteries.

Modulation transfer function

Modulation transfer function, using the concept of contrast to verify the sharpness of the lens. The horizontal axis is the distance from the center of the picture (the farther to the right, the edge of the picture), and the vertical axis is the contrast. The MTF curve is divided into different spatial frequencies (such as 10 line /mm, 30 line /mm, etc.). ), and the closer the former is to 1, the better the contrast characteristics are. The closer the latter is to 1, the higher the resolution. In addition, there are generally solid lines and dotted lines on the picture, which represent the up-and-down axis and the left-and-right axis of the picture respectively.

Multiple exposure: multiple exposure

When the same film is exposed more than once, multiple exposures are made; Suitable for shooting fireworks or other special effects.

Multi-zone evaluation and measurement: multi-zone evaluation and measurement.

The photometric system divides the whole picture into several areas (different cameras have different shapes and ways), and determines the photometric weighting ratio of each area according to the position of the subject. After all the tests are finished, exposure value is sure.

PC lens

Perspective control, or "axis shifting lens", can move the optical axis of the lens in parallel to correct the deformation of the object. For example, in architectural photography, you can use the "translation" function to correct the situation that buildings are large, small and upside down.

Range finder: ranging linkage camera

Ranging cameras, so-called binocular cameras, such as Leica M6, Hexar RF,

BESSA-R et al.' s "Real-image Linkage Ranging Camera", that is, the mechanical device of the camera uses triangulation to find the distance of the subject, so that the focusing system of the lens is linked.

Back focus: back focus

In order to cope with the high-magnification zoom lens and lightweight, the lens is divided into even groups instead of the whole group when focusing, and only the last group of lenses is moved to focus, which is called rear group focusing.

Rear curtain synchronization: Hou Lian synchronization.

Hou Lian synchronization, also known as two-curtain synchronization, will flash before the shutter Hou Lian starts to move (it is conceivable that the shutter will flash before closing, which is different from "front curtain synchronization"). It can be used when the shutter is slow and the main body is moving, and a more suitable effect can be obtained.

RGB photometry

Nikon F5' s unique photometry method can not only analyze the light and contrast in the picture, but also analyze the color of objects in the picture through 1005 RGB sensors (red/blue/green). Such as snow, blue sky, yellow flowers and so on. , easy to appear photometric deviation, can be analyzed through the rich database in the computer, to find out the best exposure value.

RMS particle properties

RMS is the abbreviation of root mean square, which measures the particle density per unit area on uniformly exposed film; It is an objective and definite film granularity. It is formulated according to ANSI standard; The smaller the RMS value, the finer the film particles.

Shutter priority: shutter prerequisite

The photographer adjusts the shutter value, and then the camera automatically measures the light to determine the aperture value; The first exposure of the shutter is more suitable for flashing or holding hands to worry about camera shake.

Slide:: positive film

Positive film is also called color review film or color positive film, commonly known as slide show. It can be divided into color positive films and black and white positive films.

SLR: SLR mirror

Single lens reflex, the so-called "monocular camera", can look at the scene in the lens from the observation window and focus it through the semi-transparent and semi-reflective mirror and prism.

Transistor-transistor logic.

The abbreviation of Through the lens means that the light measurement (AE) system measures the light through the lens, so there is no need to consider the influence of the filter.

UD glass

UD stands for ultra-low dispersion, and its refractive index and dispersion are between fluorite and ordinary glass. It can be used for large-aperture zoom lens or telescope head to improve lens quality.

USM:: ultrasonic motor

The abbreviation of ultrasonic motor first appeared in Canon EF 300mm f/2.8L USM of 1987, and now it is applied to most Canon EF lenses. The principle is to use ultrasonic vibration energy to drive rotation, and with its characteristics of low speed and high torque, to achieve the purpose of silent and fast focusing.

Halo: a dark corner of the periphery

The brightness of exposure on the negative decreases from the center to the four corners, resulting in a dark phenomenon around. The vignetting may be a natural expression caused by the lens, or it may be an improper use of the hood or filter.

X-sync: flash synchronization speed

The highest shutter speed that a camera can achieve with an electronic flash. The higher the camera, the faster the X-sync shutter.

Area system:: area exposure method

An exposure method created by Anser Adams can accurately grasp the contrast tone of photos when shooting. Firstly, the photo is divided into 1 1 region from all black to all white, and the gray part in the middle is called V region. Measure the brightness of the object, and use various control methods in the process of development and amplification until the desired result is obtained, showing the best sense of hierarchy.

distant view

Depending on the focal length of the lens (wide-angle lens or telescope head), the subject feels closer or farther away from the background. This visual effect is called perspective.

Tone and saturation (sorted by Summicron 35)

Humans can describe the concept of color in many ways, among which the recognized description methods are as follows:

1.HSB mode

Color description mode based on "human visual perception". It was invented by American Albert Henry Mancel. Color can be defined by the following three parameters:

Hue: refers to the wavelength of light waves reflected (or transmitted) by objects to the human eye. This is the color we usually see, such as red, orange, yellow, green and so on.

Saturation: refers to "the intensity or purity presented by color". Saturation shows the percentage of gray contained in the hue. For example, a saturation of 0% means full gray, and 100% means full saturation. Saturation is sometimes expressed as chromaticity, and some people translate it into chromaticity.

Brightness: refers to the lightness and darkness of a color. Generally, 0% means all black, and 100% means all white. Brightness is also called value, which translates to lightness.

2.RGB primary color mode

In human visible spectrum, "a large part" can be expressed by different mixing ratios of three primary colors of light. This is the well-known three primary colors of red, green and blue. When the three primary colors are mixed, secondary colors (blue, magenta and yellow in this case) will be produced. When the three primary colors are mixed in equal proportions, white light will be formed. This mode is usually used for lighting, video systems, movies or monitor screens. That is to say, these systems emit different proportions of colored light to present various colors, which is also called additive color.

3.CMYK mode

This is the color representation standard of magenta (M), yellow (Y), blue (C) and black (K) used in four-color printing or prepress operation. Compared with RGB mode which requires light source to produce color, CMYK mode is based on the spectrum absorbed by printing ink. When light is projected onto printing ink, part of the spectrum is absorbed by the ink, and the unabsorbed spectrum is reflected to people's eyes to "produce" color. Theoretically, the mixture of magenta, yellow and blue ink will produce black, because this black "theory" will absorb all visible spectra and let us "see" black, so it is also called subtractive method. However, ink always contains some impurities that affect the absorption effect, so the mixed color is not pure black (but brownish gray). In order to express all black, all black ink (denoted by K to avoid confusion with light blue) is introduced.

4.CIE L*a*b mode

In view of the fact that there are too many unified color standards at present, the International Standard Color Association has formulated a set of international common color expression standards in 193 1. This color system has nothing to do with printing equipment and equipment. L*a*b is represented by the vertical axis from all white to all black, and two horizontally extending faces represent colors, one of which represents red to green and the other represents blue to yellow.

5. Full color scale mode

This is a color representation method that integrates the colors that can be represented by human visible spectrum. These include "colors that the device can display" and "colors that the device can print". According to this integration method, the color expression ability is as follows: cmyk < RGB < lab.

That is, the system equipment can see and display some natural colors, but it is beyond the performance range of CMYK.

Color temperature:

The degree of color temperature is in K, which was formulated by the British physicist W.T.Kelvin. The standard of dividing color temperature is the same as that of thermometer in Celsius, but the starting point is different. The color temperature of zero degrees is equivalent to -273. 15 degrees Celsius. The calculation method of color temperature is to add 273 degrees Celsius to the temperature required for a standard black body (metal) to emit a certain color light after heating, which is the color quality of the color light. For example, the color temperature of tungsten lamp for photography is 3200K, which is the light emitted when a standard blackbody is heated to 2927 degrees. When the color temperature of light is below 4800k, it will appear orange when photographed with solar film, and blue when it is above 5200 K..