Frame rate

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The image frequency (precise frame rate ), or frame rate is a term used in film and video technology . It describes the number of individual images that are recorded or played back per period of time and is usually specified in the unit fps ( frames per second ), more rarely BpS ( picture frames / pictures per second ) or Hz . High-speed cameras can have millions of them. These are then often used for slow motion. An image frequency above the flicker fusion frequency ensures flicker-free perception. Because of the stroboscopic movement , a sequence of individual images is perceived as continuous movement.

Film and video technology

The human brain perceives successive images from around 14 to 16 images per second (individually different) as moving (but not necessarily jerk-free) scenes, which is why the frame rate in the early days of moving images ( silent movie time), after an experimental phase, is 16 Frames per second was set. At the second international congress of film manufacturers in Paris in 1909, 1000 frames per minute were specified, which corresponds to around 16-17 frames per second. However, many late silent films were made with higher frame rates, such as B. 22 frames per second recorded. With the introduction of the sound film, the frame rate was fixed at 24 Hz.

Current frame rates are 24 Hz (for many movies), 48 Hz (for lavishly produced new movies and 3D cinema), 25i / 30i Hz (for television) and 60–240 Hz (for computer games). An image sequence that is recorded with a low frame rate and played back at normal speed is called time-lapse , at a high frequency one speaks of slow motion .

Common playback frame rates in film technology
Film format frames per second
Normal 8 filmIMAX 16, 16⅔ (standard sound system ETS), 18, 24, 25 in connection with the tape speed 3 3 ⁄ 4  inches per second
Super 8 filmIMAX 18, 24 ( home theater )
16mm filmIMAX 16, 18, 20 (silent educational films ), 24, 25 ( television )
35mm filmIMAX 16–24 (silent film), 24 (cinema), 25 (television)
55mm filmIMAX 24 (cinema)
65/70 mm filmIMAX 24 ( Panavision Super 70 , Ultra Panavision 70 , Todd-AO ), 30 (early Todd-AO ), 60 ( showscan )
65/70 mm film IMAX 24 (IMAX 2D / 3D), 48 (IMAX HD)
Common playback frame rates in video and television technology
format frames per second
PAL / SECAM 25i ( interlaced = twice 25 fields, i.e. 50 fields)
NTSC b / w 30i (2 × 30 fields , i.e. 60 fields)
NTSC color 30 × 0.999 ≈ 29.97i

photography

Even with digital cameras today, a maximum frame rate is often specified with which images can be photographed in succession. However, this is often only maintained for a few photos, since the image files cannot be saved as quickly as they are created when taking the picture, especially if slower memory cards are used or images are saved in a raw data format. Modern cameras can take photos at 20 frames per second.

See also

Web links