In filmmaking, video production, animation, and related fields, a frame is one of the many still images which compose the complete moving picture.
The term is derived from the historical development of film stock, in which the sequentially recorded single images look like a framed picture when examined individually.
The term may also be used more generally as a noun or verb to refer to the edges of the image as seen in a camera viewfinder or projected on a screen.
When the moving picture is displayed, each frame is flashed on a screen for a short time (nowadays, usually 1/24, 1/25 or 1/30 of a second) and then immediately replaced by the next one.
Persistence of vision blends the frames together, producing the illusion of a moving image.
In North America and Japan, 30 frames per second (fps) is the broadcast standard, with 24 frames/s now common in production for high-definition video shot to look like film.
[a] This leads to many synchronization problems which are unknown outside the NTSC world, and also brings about hacks such as drop-frame timecode.
In film projection, 24 fps is the normal, except in some special venue systems, such as IMAX, Showscan and Iwerks 70, where 30, 48 or even 60 frame/s have been used.
The maximum frame size is 18 by 24 mm, (silent/full aperture), but this is significantly reduced by the application of sound track(s).
A system called KeyKode is often used to identify specific physical film frames in a production.
With the dominance of digital technology, modern video systems now represent the video frame as a rectangular raster of pixels, either in an RGB color space or a color space such as YCbCr, and the analog waveform is typically found nowhere other than in legacy I/O[clarification needed] devices.
So a compromise should be reached in system designs both for satisfactory image quality and affordable price.
To increase the sense of motion it is customary to scan the very same frame in two consecutive phases.
[4][5] Video and film artists sometimes use still frames within the video/film to achieve special effects, like freeze-frame shots or still motion.
[6] For criminal investigations it has become a frequent use to publish still frames from surveillance videos in order to identify suspect persons and to find more witnesses.