Glossary And Formulas Flashcards
10-bit
A video system where each colour has 1024 possible levels (0-1023).
4:4:4
Highest quality sampling for high-end transcoding, particularly for feature film. Used extensively for visual effects work. For every 4 samples of Y, there are 4 samples of CR and 4 samples of CB.
4K
An emerging set of digital video standards where the horizontal width of a picture is around 4000 pixels.
8-bit
A video system where each colour channel has 256 possible levels (0-255)
Active video
Lines in an analogue video system used for picture.
Aliasing
An artefact where insufficient chrominance information to show clean transitions between areas of significant colour difference, causes stair-stepping, noticeable on curved or diagonal edges of objects in frame.
Alpha channel
A fourth channel stored in some file formats e.g. TIFF. Not usually captured by cameras. Commonly used for encoding transparency for compositing.
Anti-aliasing
A technique used to reduce visible aliasing.
Aperture (iris)
The opening in the lens that lets light fall on the imager. Measured in f-stops or T-stops. large aperture causes shallow depth of field.
Artefacts
Unwanted features in an image, often caused by sampling or compression.
Baby mount
Receptacle for 5/8” pin from stand for a lighting fixture.
Back porch
The part of an analogue video signal prior to the active video that contains colour burst information.
Bail
Mounting point for a lighting fixture where the housing attaches to the stand.
Banding
A sampling artefact: bands of colour become visible when the bit depth does not allow enough colours to accurately show a gradient of colour.
Barn doors
Hinged flaps on a lighting fixture that allow general control of beam.
Bayer filter
A filter used in digital imagers to derive colour information. Each area of a bayer filter allows only red, green or blue light to hit the photosite beneath it.
Bit depth
Refers to the level of data in a given sample. A bit depth of 8 has 256 levels per channel (0-255).
Bit
The smallest unit of information in a digital system. A bit can have only one of two values: on or off, usually referred to as 1 or 0.
Bounce board
A polystyrene or foam core sheet held by a stand to enable a soft light source to be created from a hard source.
Brightness adaptation
Perception of the brightness of a colour can be affected by surrounding colours.
Caboose effect
An approach to film production where the final distribution format is used to make logistical decisions (named for the caboose:in the USA, this is the final car on a railway train).
Candela
A measurement of intensity from a light source (cd).
CCD (charged coupling device)
Longstanding analogue system to record video: light hits a photo-site, a chip chip converts it to a voltage. The camera converts voltage into digital picture information.
Circle of confusion:
CoC: a measure of resolving power used in Depth of Field calculations. The largest blur spot that will still be perceived by the human eye as a point.
Clipped
A colour signal beyond the limit of brightness of an imager, represented as pure white.
Closed face (in lighting)
A fixture that uses a lens
CMOS (complementary metal oxide semiconductor)
The most commonly used sensor in modern digital cameras. Light converted to voltage, amplified and converted to digital data on chip.
CMY/CMYK
A subtractive colour model whereby cyan, magenta yellow (plus black in CMYK) mix to black.
CODEC (compressor-decompressor)
A device or computer program for processing data using fewer bits of information than the original.
Colour burst
The part of an analogue video signal that is transmitted to the receiver to derive colour information.
Colour correction
Post Production process whereby colours are adjusted for aesthetic purposes.
Additive colour
A means of modelling the mixing of light whereby component (i.e. Primary) colours mix ultimately to white.
Colour temperature
A measurement of colour from a light source
Compression
Encoding data using fewer bits of information than the original
Crushed
A colour signal beyond the lower limit of brightness of an imager, represented as pure black.
CTB (colour temperature blue)
Gels to make tungsten sources cooler (toward 5,600K and higher)
CTO (colour temperature orange)
Gels to make daylight sources warmer (toward 3,200K and lower)
CTS (colour temperature straw)
Gels to make daylight sources warmer (toward 3,200K and lower but with less red than CTO.
Daylight balance
A colour temperature used to represent daylight: usually around 5,600K
Depth of field (DoF)
The area along the z axis that appears to be in acceptable focus
Diffusion gel
A gel used to soften hard light sources
Digital cinema distribution master (DCDM)
A common file used in the production of digital cinema. Uncompressed, unencrypted and not for distribution itself. The set of files is used to create the DCP.
Digital cinema package (DCP)
The files that go to the cinema for projection. Compressed (usually using JPEG2000) and encrypted to prevent piracy.
Dithering
A means of mixing adjacent shades to make banding less apparent.
Edit decision list (EDL)
A lost of all edit points for picture and sound. Traditionally written by hand, now usually created by NLE.
Ellipsoidal reflector:
Creates a beam that focuses to a point
Exposure index (EI)
A working measure of the speed of an imager, usually based on the ISO modified by filtration or desired exposure results.
Exposure time
The amount of time the imager is allowed to collect light. This is controlled by the shutter in a film camera. Also known as shutter speed and measured in fractions of a second. Long exposure time (low shutter speed) causes motion blur.
Fall off
In lighting is the area between the edge of the spread and the edge of the beam.
FireWire
An interface for transmitting data, commonly used for digital video systems.
Footcandle (fc)
A unit of illumination common in the US and the film industry in general 1fc=10.76lux)
Fixture (in lighting)
A lamp used in film or TV
Flag (in lighting)
Opaque matte black cloth on a frame that blocks light from hitting certain areas.
Flood (in lighting)
Beam is roughly even over the lit area.
Fluorescent
Lighting technology with good power efficiency and cool running temperature, producing very even soft beam
Fresnel lens
Compact lens with the same focusing ability as a conventional lens, made thinner by removal of non-refractive glass area.
Front porch
The part of an analogue video signal that leads up to the horizontal sync pulse.
F-stop
A measure of aperture based on a standardised design specification
Gamma
A function applied to a video signal to alter the output, i.e. To achieve a look or to alter exposure.
Gamut
The range of hues available within a colour space
Gel
Heat resistant transparent polyester sheets used to accurately change the colour of light.
Graticule
The face plate of a waveform monitor or vectorscope
Hard light
Light that casts distinct shadows
High definition (HD)
A set of digital video specifications used worldwide. Common variants include 720p, 1080i and 1080p
HMI (mercury medium-arc iodide)
Efficient lighting technology often used for daylight sources.
Hot spot
The brightest area of a beam of light
Housing
The main body of a lighting fixture
HSV
A colour model used commonly in colour grading. Comprises hue (the perception of a specific wavelength), saturation (the amount of hue present) and value (brightness or luminance).
Hyperfocal distance (H)
The closest distance where both objects at infinity and closer objects are in acceptable focus
Illumination
The amount of light falling onto a subject area
Imager
The component of a camera that captures the image i.e. The digital sensor or film
Incident light
Light falling onto a subject or area
Incident meter
A device for measuring incident light
Interframe coding
Operations done over more than one frame
Interlace
Each frame is recorded in two fields: one comprising odd lines, the other even lines
Intraframe coding
Operations done within an individual frame
IRE
A scale used to measure luminance in video (stands for institute of radio engineers)
ISO
The sensitivity to light of an imager. In film this is referred to as film speed. The higher the ISO, the more sensitive to light the imager is. High ISO settings often result in noise or grain in the image and lower colour fidelity/
Junior mount
1 1/8” pin (spud) that goes into a receptacle on a stand for a lighting fixture.
Lantern
A lamp used in film or TV
Lateral colour adaptation
Strong background colours will impart a perceived colour cast on foreground objects.
Latitude
The dynamic range of an imager: i.e. How many f-stops between under and over exposure.
LED (light emitting diode)
A power efficient, cool running, lighting technology
Length (of a lens)
The focal length measured in millimetres
Local colour adaptation
The way the human visual system attempts to adapt reading colour under changing light conditions. the brain always seeks to establish a base white.
Lossless compression
Reduces the amount of storage (or bandwidth) required but all date is intact.
Lossy compression
Can reduce the amount of storage (or bandwidth) required but some data is lost.
Luminaire
A lamp used in film or TV
Lux
Metric unit of illumination
1lux=0.093fc
Metadata
Extra information stored alongside video data in a file. This might include contextual information (camera model, lens settings, times etc.)
MIRED (micro reciprocal degrees)
A measurement used to calculate shifts in colour temperature.
Net
Stand-mounted devices for reducing the light from a fixture
Neutral density filter
A filter used on a camera to reduce the amount of light entering the lens without affecting colour.
NLE
Non-linear editor. An editing system permitting cuts to be made non-sequentially.
NTSC (national television system committee)
The specification for standard definition TV in the USA, Japan, the Americas, Polynesia.
Open face (in lighting)
A fixture that does not use a lens
PAL (Phase alternating line)
The specification for standard definition TV in the UK, Europe, some of the Middle East and Africa.
PAR
A parabolic reflector lamp
Parabolic reflector
Creates an even beam with parallel rays
Pedestal
Refers to the signal level representing black
Photosites
The sensitive areas of a digital imager:usually sensitive only to brightness: see bayer filter
Progressive scan
Each frame is recorded in one pass, exposure or scan. (The ‘p’ in 1080p)
Quantization
The reducing of luminance or chrominance information into bit depth
RAW
Unprocessed 12 bit linear colour space
Reflected light
Light coming from a subject or area
Resolution
The amount of detail captured by an imager. Usually measured in a video as pixels: e.g. 1920x1080
RGB
An additive colour model whereby red, green and blue channels are mixed to derive different colours. Commonly used for TV recording and reproduction.
Run-length Encoding (RLE)
A means of aggregating like areas of data designated by: number of pixels, R value, G value and B value.
Sampling rate
Refers to how many samples are taken in one second, measured in cycles per second (Hz or MHz).
Sampling
A means of approximating and analogue signal digitally
Scrim
Mental mesh screens that reduce light from a fixture
SECAM
(Sequential coluleur a memoir) the specification for standard definition TV in France, Russia and much of Eastern Europe.
Shiny Board
A large reflector on a stand to bounce light into an area.
Snoot
Extension to a housing fixture that limits the beam to a circular pattern
Soft light
Light that casts minimal or diffuse shadows
Spatial compression
Compression of information within a frame
Speed (of a lens)
The largest aperture the lens has
Spherical reflector
Creates a broad beam-used in Fresnels and floods
Spot (lighting)
Beam is brightest in the centre and falls off rapidly
Spot meter
A device for measuring reflected light from a subject
Spread or beam area
In lighting is the main beam area that has a roughly even level of illumination
Subsampling
A technique whereby luminance and chrominance information is sampled independently and at different levels of detail.
Super black
A video signal of 3.5 IRE (1-15)
Telephoto
Refers to a lens with a long focal length
Temporal compression
Compression of video information by looking for repeated data between different frames
Thick negative
A slightly over-exposed film negative
Thin negative
A slightly under-exposed film negative
T-stop
A measure of aperture based on actual measured transmission of light.
Tungsten balance
The colour temperature of studio tungsten lamps: around 3,200K
Ultra-high definition (HD)
An emerging set of digital video specifications, where resolution is greater than HD.
Vectorscope
A device used to measure chrominance
Wattage
How much energy a piece of equipment uses.
Waveform monitor
A device used to measure luminance in a video signal
White balance
The colour temperature used to represent white in a video system
Wide angle
Refers to a lens with a short focal length
Y:CR:CB
A colour model used in sampling. Components are Y (luminance), CR (chrominance-red) and CB (chrominance-blue) green is calculated because our eyes are more sensitive to green
Zebra
A stripy horse. Also a type of reflected-light meter commonly found on video digital cinema cameras.
Calculating necessary illumination
fc=(25xf^2)/txEI Lux=(269xf^2)/txEI fc=footcandles, F=T-stop/F-stop, T=exposure time, EI=exposure index
Calculating depth of field
H=F^2/fxCoC
ND=HxS/H+(S-F)
FD=HxS/H-(S-F)
H=hyperfocal distance, F=focal length of lens, f=f-stop, CoC=size of circle of confusion, ND=near distance, FD=far distance, S=distance from subject to camera
Storing video information calculation
Storage per frame (bytes)=resolutionx3xbit depth/8
(3 colours and 8 bits in 1 byte)
Storage per second=storage per frame frame rate
X60=minutes, X60=hours
Inverse square rule: calculating falloff of light
The level of incident illumination is inversely proportional to the square of the distance from the source
fc=cd/ft^2
Lux=cd/m^2
Calculating a MIRED shift
MIRED shift=1,000,000/target temp - 1,000,000/current temp
Calculating transmission of light with gels
Required illumination =target illumination/gel transmission
Ampacity
The maximum amount of current the cable can handle in amps
Amperage
Or current (I) the rebate of flow of electrons measured in amps (A)
AWG
American wire gauge: a rating indicating a cables current carrying capacity
CMIL
Is the measurement of the cross sectional area of the cable
Line loss
The drop in voltage in a cable due to resistance
Resistance (R or K)
The opposition to flow measured in ohms♎️
Tie in
A connection to mains electricity
Voltage (E)
The force that current flows through resistance measured in volts (V)
Wattage or power (P)
The total power being used measured in watts (W)
Power measurement
P=IxE
P=power
I=amperage
E=voltage
Calculating voltage drop (line loss)
VD=(2xRxIxL)/Cmil R=resistance I=amperage L=length Cmil=cross section of cable
