High-Speed Camera Definitions
Aperture - A set of gated blades or similar mechanism inside of a camera lens incrementally adjustable to control the entry and angle of incoming light rays.
ASA Rating - American Standards Association exposure index numbers.
Back Focus - A type of focus concerning the distance of the rear lens element to the image sensor similar to the focal flange length. See Depth of Focus.
Bit Depth (Sensor) - A value used to calculate the number of shades a pixel can register. 8-Bit is 0 to 28= 0 to 256 shades; 12-Bit is 0 to 212=0 to 4,096 shades. Some manufacturers multiply this value by 3 for a Red-Green-Blue color model to seem better than a competitor (12-Bit as 36-Bit Color).
Bokeh - An aesthetically pleasing, mainly subjective, out-of-focus quality of a lens.
C-Mount (Lens) - A small, relatively inexpensive lens type with a 1 inch diameter - 32 threads per inch mount (1-32 UN A2). The flange focal length is 17.526mm (0.69in).
CCD (Sensor) - Charge-Coupled Device
CMOS (Sensor) - A Complementary Metal-Oxide Semiconductor Active Pixel Sensor
Circle of Confusion - The measured diameter on the focal plane (image sensor or film) of a single point source of light including diffraction rings. The circle of confusion is minimal when the object is in focus.
Depth of Field - The range of objects in front of the lens that are acceptably sharp or in-focus (farthest object minus nearest). More specifically defined by a Circle of Confusion measurement.
Depth of Focus - The range of image distances (image sensor or film position) behind the lens that result in an acceptably sharp or in-focus captured image. See Back Focus.
Exposure Time - The amount of time that light is being recorded on an imaging plane. It is displayed as either a fraction of a second which is common for photography (1/8,000 for example), a decimal number which is common for scientific applications (0.000125), or indirectly as a shutter-angle in relation to a frame period or interval which is common for cinematography. Many professional high-speed video cameras specify exposure time in microseconds (125µs). See Shutter Speed.
EF-Mount (Lens) - A lens type developed by Canon with a three-lug bayonet mount. The mounting diameter is 54mm with a flange focal length of 44mm. More commonly associated with Canon EOS lenses.
F-Mount (Lens) - A lens type developed by Nikon with a three-lug bayonet mount. The mounting diameter is 44mm with a flange focal length of 46.5mm.
F-Number - The ratio of focal length to effective aperture diameter.
F-Stop - See F-Number.
F-Sync - Frame Synchronization when operating multiple cameras.
Frame Rate - The rate per second that image frames are displayed. More commonly, it refers to the Sample Rate that frames are captured by a camera.
High-Speed Framing Camera - A high-speed camera that captures images on multiple image planes or multiple locations on the same image plane allowing increased sample rate over conventional high-speed cameras.
High-Speed Streak Camera - A high-speed camera recording a series of thin, line-sized images sequentially recorded across an imaging plane for three-dimensional acquisition (spatial data, intensity, and time).
High-Speed Video Camera - A camera capable of recording images at a rate over 250 frames per second with exposures faster than 0.001 sec (1/1,000).
ISO Rating - International Organization for Standardization exposure index numbers; the successor to ASA ratings. Doubling the ISO value represents a doubling of sensitivity to light.
Macro (Lens) - A lens designed to focus at very short object distances, capturing small subjects at reproduction ratios near or above 1:1 (life size on the sensor).
Megapixel - One million pixels (1,048,576 = 1024² exactly); resolution width × height ÷ 1,000,000.
Micro (Lens) - Nikon’s designation for its macro lenses (Micro-NIKKOR). Separately, microlenses are tiny lens elements bonded over each pixel of an image sensor to increase light-gathering efficiency.
Pixel - The smallest light-sensitive element of an image sensor (picture element). Pixel size is commonly stated in micrometers (µm) and is a key input for field-of-view and motion-blur calculations.
PL-Mount (Lens) - A large, relatively expensive Positive Lock lens type developed by Arri with four notched flanges with a locking ring. It has a 54mm diameter and a 52mm flange focal length.
Resolution - With most CMOS high-speed cameras this term refers to the horizontal and vertical dimension of an image frame in pixels (1024x1024, 1280x800, 1920x1080, etc.).
Sample Rate - The rate at which an electronic device captures data. See Frame Rate.
Schlieren Imaging - An optical technique using collimated light and a knife-edge cutoff to visualize refractive-index gradients in transparent media — making pressure waves, heat plumes, and gas flows visible. Paired with high-speed cameras for dynamic visualization.
Shadowgraph Imaging - A simpler relative of schlieren imaging: light passing through refractive-index disturbances casts a shadow pattern. Long used in spark ranges for ballistic study; well suited to strong disturbances such as shock waves.
Shutter Speed - The Exposure Time in reference to cameras with physical shutters. See Exposure Time.
Slow Motion Camera - A camera that is capable of capturing images at a faster rate than which they will be replayed. A slow motion camera is not necessarily a high-speed camera.
Sub-Microsecond Photography - A type of photography technology utilizing common DSLR cameras operating in a dark environment with flash or strobe units capable of exposures less than 1 microsecond (<0.000001 sec.).
Ultra High-Speed Camera - A camera capable of recording images at a rate over 10,000 frames per second.
(CSR) Current Session Reference - A black reference image calibration feature on Vision Research high-speed cameras to correct image quality including color.
(EDR) Extreme Dynamic Range - A secondary exposure setting on Vision Research high-speed cameras used to prevent saturation of bright areas.
(GB) Gigabyte - Data storage capacity of 10243 bytes or 1,024MB (1,073,741,824 bytes).
(KB) Kilobyte - Data storage capacity of 10241 bytes or 1,024B (1,024 bytes).
(MB) Megabyte - Data storage capacity of 10242 bytes or 1,024KB (1,048,576 bytes).
(TB) Terabyte - Data storage capacity of 10244 bytes or 1,024GB (1,099,511,627,776 bytes).