The technological transition from ciné film to analog video represented a fundamental shift from chemical to electronic detection and recording of light. The transition from analog to digital video contains no such shift and, from a technological point of view, proceeded in piecemeal fashion. As described above, by the middle of the analog video era, image data were first digitally detected using a CCD, then stored in analog form on tape, displayed in analog on a CRT screen, and finally converted back to digital form for analysis. Later in this era, digital video tape formats appeared that moved the storage encoding to a digital format while continuing to use tape as the medium. Thus, the analog era was actually digital in many of its internals by the early 1990s, and by the end of the decade, commercially available high-speed analog video cameras were capable of recording at more than 1000 frames s−1, yet still used standard VHS tape for storage. In the face of this piecemeal transition, we mark the shift to the digital video era as the point where data were collected, stored and analyzed using digital technology without any intermediate analog steps. In general terms, this came about once personal computer volatile and non-volatile storage (i.e. RAM and hard disk) were large enough for video display and especially storage (Fig. 3A).

As with many other technological advances described here, a few pioneering researchers with specific needs and appropriate skill-sets developed custom fully digital workflows well before the appearance of ‘off the shelf’ equipment with the same capabilities. For example, some groundbreaking early experiments directly coupled a computer frame-grabber board to a CCD camera and used custom computer programs to analyze the live video image to extract relevant kinematic parameters (Godden and Graham, 1983; Dean, 1991; Winberg et al., 1993; Schurmann and Steffensen, 1994). Because the images were processed as they were acquired, it was not necessary to store the videos, which worked around the absence at the time of low-cost and high-capacity digital storage media. As these studies demonstrate, a purely digital workflow was possible with computer technology (i.e. an Apple II) as early as 1983 and the data could be generated instantaneously. However, for most biomechanics research questions, such real-time video analysis was infeasible and analog tape fed by CCD sensors remained the dominant technology. Interestingly, real-time video workflows still have a place in current research (e.g. Fry et al., 2009), where they enable closed-loop experiments on animal sensing and control of movement.