essential skills: digital photography in available light
Gaussian Blur A fi lter used for defocusing a digital image.
Genre Style or category of photography.
Gigabyte A unit of measurement for digital fi les, 1024 megabytes.
Gray card Contrast and exposure reference, refl ects 18% of light.
Grayscale An 8-bit image used to describe monochrome (black and white)
images.
Guide number Measurement of fl ash power relative to ISO and fl ash to subject
distance.
Halftone Commercial printing process, reproduces tone using a pattern
of dots printed by offset litho.
Hard/harsh light Directional light with defi ned shadows.
High Dynamic Range (HDR): An image created from multiple exposures where the subject
brightness range exceeded the latitude of the image sensor.
High key Dominant light tones and highlight densities.
Highlight Area of subject giving highest exposure value.
Histogram A graphical representation of a digital image indicating the
pixels allocated to each level of brightness.
Hot shoe Mounting position for on-camera fl ash.
Hue The name of a color, e.g. red or green.
Hyperfocal distance Nearest distance in focus when lens is set to infi nity.
ICC profi le A color profi le embedded into the digital image fi le to ensure
color consistency.
Image sensor Light-sensitive digital chip used in digital cameras.
Image size The pixel dimensions, output dimensions and resolution used to
defi ne a digital image.
Incandescent Tungsten light source.
Infi nity Point of focus where bellows extension equals focal length.
Infrared Wavelengths of light longer than 720nm invisible to the
human eye.
Interpolation A method of resampling the image to alter its pixel dimensions.
Inverse square law Mathematical formula for measuring the fall-off (reduced
intensity) of light over a given distance.
Iris Aperture/diaphragm.
IPTC Metadata information standard designed by the International
Press and Telecommunications Council.
ISO Sensitivity rating - International Standards Organization.