212 
Psyche 
[March 
Analysis 
Analysis of audio-visual synchrony must consider the following 
factors : 
1 ) A video field is scanned from top of the screen to the bottom 
once in 16.67 msec at a maximum resolution of 262.5 lines per field; 
the horizontal sweep time for a line is 0.0635 msec. The vertical 
blanking interval (retrace time for the electron-gun to move from 
bottom of the screen to the top) requires up to 21 lines, and sub- 
tracted from the maximum resolution leaves a net resolution of 241.5 
lines per field with a net duration of 15.5 msec, and a vertical blank- 
ing interval of 1 to 1.2 msec. 
2) A video frame consists of two interdigitating video fields with 
a total net duration of 31 msec and a total net resolution of 483 
lines. 
3) Transduction of light and electronic impulses can be regarded 
as instantaneous, however the speed of sound in air is a variable. 
Near sea level, at 37 C and no greater than 10 cm from the micro- 
phone, one can calculate that the maximum time interval between 
sound production and electronic transduction is no greater than 0.4 
msec and can be neglected as an important factor. 
4) A crucial discrepancy in visual-acoustic synchrony and visual 
analysis of movements is the time taken by the electron-gun of the 
video camera to trace any action within a field. This factor causes 
three time-related distortions in the image which must be considered 
in the analysis, namely (a) vertical loss of resolution, (b) excessive 
curvature of a rotating image, and (c) inability to record events 
which occur after a scanning trace has passed until the next field scan. 
5) Vertical loss of resolution: the image formed during a single 
field has a maximum vertical resolution of only 241.5 lines per field 
whereas a 16 mm optical-film frame has 50-60 lines of resolution per 
mm (at the center) or about 700 to 800 lines of resolution overall 
(allowing for loss of about 20 lines of resolution at the front and rear 
edge of the frame). On the other hand, the horizontal resolution of 
a good video system probably approaches that of a comparable optical- 
film system. However evaluation of information content of a video 
field and an optical film frame encompassing 15 msec is obscured by 
the next considerations. 
6) Excessive curvature of rotating image: the time required for 
scanning a single field naturally produces a distorted image in any 
movement having lateral components. Plate ia-e illustrates this 
