Camera Output
What are some common terms associated with camera development and manufacturing?
As important as understanding camera terminology, features and accessories is understanding the industry that surrounds them. A familiarity with these terms should help you navigate the mazes of acronyms, abbreviations and industry standards that await you.
Gamma video related - A term that describes quality of data transfer of collected light input to light output. In most systems data is corrupted at some point during transfer and so requires gamma correction.
Horizontal Drive Signal [HD]/ Vertical Drive Signal [VD] video related - each is a signal that comprises half of an image’s information. The HD signal combined with the Vertical Drive Signal or VD signal are collected and synchronized with an external viewing or receiving device.
Sony High Definition Video System ™ video related - Sony’s HDVS uses a 1125 line rate and 16:9 aspect ratio, providing a sharper image than the standard viewing resolution and ratio. Essentially, the image requires less modification, scaling and distortion to be viewed on HDVS viewing devices than standard definition image viewing devices.
What are some often referenced camera parts or associated accessories that I should be aware of?
Following is a list of parts and accessories that are common to most cameras on the market. Knowing the function of these devices is paramount to making an informed decision on your next camera purchase.
Aperture - The opening in the center of the iris that allows various levels of light to pass into the camera. The larger the aperture, the larger the opening, thus the more light allowed into the imager. Aperture size is generally referred to by measure of f/stops.
Charge Coupled Device [CCD] - A semiconductor that collects light information collected from various sensors. The device can create an electrical output analogous to the amount of light collected by the sensors. Often this information is used to automatically adjust aperture size to compensate for various lighting conditions automatically.
Camera Control Unit [CCU] - A device stationed on a camera that electronically adjusts the focus, angle of view, and scene of its associated camera head.
Iris - The adjustable mechanism that creates and adjusts a camera’s aperture. The iris is effectively the outer ring the center of which forms the aperture. The thicker the ring (iris) the smaller the hole at its center (the aperture) and visa versa.
ND - A filter placed behind the camera’s lens that reduces the overall amount of light contacting the imager. An ND filters extreme light conditions greater than what an aperture could compensate for.
What are some common terms used to reference imaging properties and characteristics
Following are a list of terms commonly used to communicate about the details or specification of a cameras output capabilities.
Chrominance - The signal used in image reproduction systems that communicates the level of color in an image. A black and white image, for instance has a zero Chrominance value.
Committee Consultative Internacional des Radio Communications [CCIR] - video related, This is the standard video signal for black and white television signals. The CCIR has a line rate of 625.
Electronic Industries Association [EIA] video related - The monochrome, or black and white version of the NTSC video signal. The EIA signal has a line rate of 525.
Field video related - A reference particular to television frame rates. A field is constituted by half of a television frame signal. The field is composed of half of the frame’s horizontal lines (either even or odd). When corresponding fields are interlaced they create the full image of one frame.
Horizontal Resolution - Resolution is specified by horizontal measure. The Horizontal Resolution measures how closely pixels across a line are placed and read by a viewing system.
Interlace Scanning - The method by which one half of the horizontal lines of a television frame are partitioned to a particular field while the remaining lines are distributed to another. The signals from alternating adjacent lines are split (odds in one field evens in another) and interlaced upon distribution to a video output to be read as a single frame.
Infrared Light [IR] - Light waves on both ends of the spectrum that fall outside of the range visible to the unaided human eye.
Luminance - The measure of brightness of the Y or gray scale portion of a television signal.
Lux - The metric measurement of light intensity. 10.76 lux is equivalent to 1 footcandle.
National Television System Committee [NTSC] video related - The standard for color television signals in the United States. The NTSC signal is 525 horizontal lines per frame and 30 frames per second.
Phase Alternating Line [PAL] video related - The European color video standard. The PAL signal is 625 lines per frame with 25 frames per second. PAL and NTSC signals are not compatible and cannot be viewed on a single image viewer.
Pixel - The smallest bit of signal information processed by a video viewer.
Raster video related - The pattern by which a television or video image viewer refreshes frames. Generally the raster pattern moves from left to right and from top to bottom. The NTSC refreshes a frame 30 times every second.
RGB - This is the common abbreviation for Red, Green and Blue, the primary colors of light mixed to create video images. An RGB system delivers each color signal from an isolated source over separate wires to the display device. Generally RGB systems produce high quality imaging and is used by most computers.
Resolution video related - A measure of definition on a television or other video viewing device. The horizontal resolution is limited by bandwidth and describes the number and detail of pixels across a given horizontal line. The vertical resolution is limited by the total number of horizontal lines scanned into a single frame. The higher the vertical and horizontal resolution, the sharper the image that the viewer produces.
RS170 video related - Synonymous with EIA. The monochrome, or black and white, version of the NTSC signal.
Sync - The common abbreviation for synchronize. The sync is the pulse that maintains the vertical and horizontal scanning process on a video imaging device.
Tri-level Sync video related - This refers to the type of synchronization signal used in a HDVS television system. The faster the scan or refresh rate of a signal, the sharper and more dynamic image is produced.