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 G-type lenses Nikkor AF-D lenses introduced in 2000. They don't have an aperture ring. Aperture setting is made through a "Sub-Command Dial" on modern auto bodies. G lenses were designed to weight less and be less expensive than their counterparts with an aperture ring. AF bodies without a "Sub-Command Dial" can use G-type lenses in Program and Shutter priority modes only. The first was the 70-300mm f/4-5.6G AF. A G lens, being an AF-D lens, provides Distance information to the camera body.
GammaThe values produced by a monitor from black to white are nonlinear. If you graph the values, they form a curve, not a straight line. Gamma defines the slope of that curve at halfway between black and white. Gamma adjustment compensates for the nonlinear tonal reproduction of output devices such as monitor tubes. Gray Gamma 1.8 matches the default grayscale display of Mac OS computers. Gray Gamma 2.2 matches the default grayscale display of Windows computers.
GamutThe total range of colors produced by a device. A color is said to be "out of gamut" when its position in one device's color space cannot be directly translated into another device's color space. For example, the total range of colors that can be reproduced with ink on coated paper is greater than that for uncoated newsprint, so the total gamut for uncoated newsprint is said to be smaller than the gamut for coated stock. A typical CMYK gamut is generally smaller than a typical RGB gamut. The most appropriate gamut for Internet display is sRGB.
GIFCompuServe Graphics Image Format. A raster-oriented file type for image sharing across multiple platforms, either 1-bit or 8-bit, rendering from 2 to 256 colors or shades of gray.
GradationThe tonal contrast range of an image. Also the range of light and dark tones in a scene that a film or digital sensor is capable of registering, and gradual changing of one tint or shade into another in very small degrees.
GradeRefers to the contrast rating of black and white enlargement papers. Zero is the lowest contrast and 5 is the maximum contrast.
Graduated FilterOr “Gradated” Filter. A filter that is not uniformly dense, but that gradually changes its density across the filter’s field. A Graduated neutral density filter is clear from one edge to approximately the middle of the filter, then gradually increase in density towards the opposite edge. Colored gradated filters gradually change color density across the filter’s field. Used to balance the light of a scene with overly bright highlights.
GrainExposed and processed silver halides on the film emulsion that turn black and form miniature "grain" that make up the image on a piece of film. The equivalent efect at high ISO in digital photography -which is grainless- is "noise".
Gray ScaleAn image made up of varying tones of black and white. Grayscale images are distinct from black-and-white images, which in the context of computer imaging are images with only two colors, black and white; grayscale images have many shades of gray in between. The 256 gray levels system divides the gray scale into 256 sections with black at 0 and white at 255.
Ground GlassFrosted glass used as a viewing mechanism in cameras without prisms. The glass is placed so that the lens projects the image against the glass for focusing and composition purposes.
Guide NumberA number used to describe the output capacity of a flash. Usually measured using an ISO sensitivity or speed of 100. Divided by the distance from flash to subject it yields aperture.
HazeAtmospheric condition characterized by fine particles of dust, smoke or moisture in the air, causing loss of contrast in an image because of light scattering.
High Eye pointApplied to a viewfinder that allows a user to see the entire frame in the viewfinder from a close distance from the eyepiece, for eyeglass-wearing digital photographers.
High KeyHigh contrast with mostly highlights and little shadow detail.
HighlightsThe bright to white parts of an image.
HistogramA representation of a frequency distribution by means of rectangles whose widths represent class intervals and whose areas are proportional to the corresponding frequencies. A graph defining the contrast and dynamic range of an image.
Hot ShoeAccessory holder usually built on top of the camera to mount a flash and other accessories. It has the necessary electric contacts to communicate with a dedicated speedlight.
HueColor. Gradation of color. Also, the attribute of colors that permits them to be classed as red, yellow, green, blue, or an intermediate between any contiguous pair of these colors.
Hyperfocal DistanceThe closest point at which a camera can be focused where the depth of field includes infinity, starting at half the hyperfocal distance.
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IF (Internal Focusing) SystemA system used where the internal elements in the lens are the only parts that move during focusing, i.e. This prevents the physical length of the lens from changing, or the lens barrel rotating; allows for faster focus, reduces aberrations, and facilitates use of filters that require specific alignment such as polarizers and graduated neutral density.
ImageA two-dimensional representation of a scene.
Image EditorA computer program that enables adjustments to a digital photo to improve its appearance. With image editing software, it is possible to darken or lighten a digital photo, rotate it, adjust its contrast, colors hue and saturation, crop out extraneous detail, remove red-eye and more. Adobe® Photoshop®, is the professional image-editing standard.
Image PlaneThe area at which a lens forms an image, i.e. the film plane if, and when focused correctly.
Image ResolutionThe number of pixels in a digital photo is commonly referred to as its image resolution.
Incident LightLight as measured as it falls on a surface, rather than light reflected from a surface.
InfinityIn relation to camera focus: the horizon.
InfraredLight not visible with the human eye. Measured at the red end of the spectrum. Can be photographed with special film.
Infrared Compensation IndexAn index on a camera lens used to compensate focusing using infrared film. With most lenses, the plane of sharpness for infrared film is slightly farther away than for normal visible-light photography.
InkjetA printer that places ink on paper by spraying droplets through tiny nozzles.
Inverse Square LawA proven statement in physics, repeatable through experimentation. A given physical quantity (as illumination) varies with the distance from the source inversely as the square of the distance. As applicable to flash photography, doubling the flash-to-subject distance reduces the light falling on the subject to one-quarter.
IR SettingMark on lenses for focusing infrared film.
ISOThe International Organization for Standardization (ISO), based in Geneva, is a worldwide federation of national standards bodies from over 150 countries, one from each country. ISO is a non-governmental organization established in 1946. The mission of ISO is to promote the development of standardization and related activities in the world with a view to facilitating the international exchange of goods and services, and to developing cooperation in the spheres of intellectual, scientific, technological and economic activity. ISO's work results in international agreements, which are published as International Standards. "ISO" is not an acronym, it is a word, derived from the Greek isos, meaning "equal", which is the etymological root of the prefix "iso-" that occurs in a host of terms, such as "isometric" (of equal measure or dimensions) and "isonomy" (equality of laws, or of people before the law). As applied to photographic film or digital sensors, it refers to its speed or sensitivity in conjunction with a number, like ISO 100, twice as "fast" as ISO 50.
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JaggiesSlang term for the star-like appearance of angled or curved lines in digital imaging.
JCIIJapan Camera and optical instruments Inspection and testing Institute, founded in 1954. Formed to inspect all cameras and lenses exported from Japan in order to maintain quality standards.
JPEGAcronym for Joint Photographic Experts Group that describes a digital image file format standard in which the size of the file is reduced by compression. A JPEG image file name carries the extension "jpg". JPEG compression is "loosy", meaning it looses some image information as opposed to other formats like TIFF. A "high quality" JPEG file looses less than a "low quality" JPEG file.
JuxtaposeThe placement of two objects close together or side by side for comparison or contrast. At times to illustrate the scale in an image, or to contrast old and new, old and young, tall and short, etc.
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K (Kelvin)Thermodynamic temperature scale measurement. In 1933, the International Committee of Weights and Measures adopted the temperature at which water, ice, and water vapor coexist in equilibrium as a fixed point, the "triple point of water"; its value was set as 273.16. The unit of temperature on this scale is called the Kelvin, after William Thompson Lord Kelvin, and its symbol is K (no degree symbol used). In digital photography it is used to measure the color temperature of light at different wavelengths.
Key LightWhen lighting a digital photographic subject, the main light source.
KeystoningDistortion of a projected image when the projector is not directed perpendicular to the screen. Also applied to the convergence of vertical lines in tall buildings when not digital photographed with a Perspective Control (PC) lens.
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