FILM FRAME

Film Frame:

In filmmaking, video production, animation, and related fields, a film frame or video frame is one of the many still images which compose the complete moving picture. Historically, these were recorded on a long strip of photographic film, and each image looked rather like a framed picture when examined individually, hence the name.

The term may also be used more generally as a noun or verb to refer to the edges of the images as seen in a camera viewfinder or projected on a screen. Thus, the camera operator can be said to keep a car in frame by panning with it as it speeds past.

When the moving picture is displayed, each frame is flashed on a screen for a short time and then immediately replaced by the next one Persistence of vision blends the frames together, producing the illusion of a moving image.

The frame is also sometimes used as a unit of time, so that a momentary event might be said to last 6 frames; the actual duration of which depends on the frame rate of the system, which varies according to the video or film standard in use. In North America and Japan, 30 frames per second is the broadcast standard, with 24 frames now common in production for high-definition video. In much of the rest of the world, 25 frames is standard.

In systems historically based on NTSC standards, for reasons originally related to the color subcarrier in analog NTSC TV systems, the exact frame rate is often the nominal frame rate divided by 1.001 --so, for example, a nominal 30fps sequence is actually shot at 30/1.001=29.97002997...fps. This leads to many synchronization problems which are unknown outside the NTSC world, and leads to hacks such as drop-frame time code.  

In film projection, 24 frames is the norm, except in some special venue systems, such as IMAX, Showscan and lwerks 70, where 30, 48 or even 60 frames have been used. Silent films and 8mm amateur movies used 16 or 18 frames.