It is the canon law, to which Egyptian artist were mandated to regularize dimensions and scale. A guideline for Egyptian artist to follow.
Added 10/03/09: According to the law, the human body (as depicted in their art) must be 18 units length to the hair lines and just under 19 to the top of the head. The bellybutton should be at 11 units length. This is beginning the measurement from the soles of the feet.
Basically, you take 19 equal-in-high units and you draw the hair line at number 18 and bake sure the bellybutton ends up in the 11th unit.
During this period (as stated by the previous answer), it was literally mandated for artists to follow these rules (freedom anyone?). As known to artists, a canon is the basic model or rule that characterizes a style.
A canon of proportions
canon
A canon is a set of rules regarding pose, proportions, thickness of line, colours, style of dress and so on; it applies equally to drawings as well as carvings and sculpture.The rule (canon) in ancient Egyptian art was always that things should be depicted from their most recognisable viewpoint - even if some other part of the same object was being seen from a different viewpoint. Shoulders, for example, would be hard to understand if drawn from the side - they are always depicted as if seen from the front, while the arms, stomach and legs are always seen from the side. Nobody believes that real ancient Egyptians ever stood like that - it was simply the traditional way of drawing.For setting out the proportions of the human figure, the canon changed over time. In the early scheme six horizontal guidelines intersected the vertical median lines of the body to define its proportions. From the Middle Kingdom, the human figure was fitted into a grid 18 squares high (to the hairline).In the later period the grid scheme was changed to 21 squares high (to the eyes) - the differences in proportion are tiny and can not normally be observed without measurement.
The Greek sculptor Polykleitos designed Doryphoros(Spear-Bearer),as an example of the "canon" or "rule", showing the perfectly harmonious and balanced proportions of the human body in the sculpted form, about 440 BC.
The Greeks used idealism in sculpture, representing people perfectly. That is when you see canon of proportions, and figures such as Doryphorus. This style, however, developed into realism, which is closer to an honest depiction of an individual.
proportions are used in scale factors; scale factors ARE proportions
They are other proportions.
Proportions of differing proportionality
The Canon ribbon is used as a part of Canon's machines. For example, the Canon ribbon might be used for Canon's printers and for Canon's digital cameras.
Nikon D60 Canon Rebel XSi Canon A590 Canon SD950 Nikon S51 Canon SD890 Canon SD790 Canon Sd770 Sony T200 Canon G9
HD video proportions are 1024x720 :)
The Canon A-1 used FD mount manual-focus lenses. The earlier FL Canon lenses are also usable on the Canon A-1, but metering is a bit more cumbersome. The current Canon EF mount was introduced in 1987 for auto-focus lenses. There is no compatibility between FD and EF lens mounts. The Canons with FD mount include: Canon F-1 (1971) Canon FTb (1971) Canon FTbn (1973) Canon EF (1973) Canon TLb (1974) Canon TX (1975) Canon F-1n (1976) Canon AE-1 (1976) Canon AT-1 (1977) Canon A-1 (1978) Canon AV-1 (1979) Canon New F-1 (1981) Canon AE-1 Program (1981) Canon AL-1 (1982) Canon T50 (1983) Canon T70 (1984) Canon T80 (1985) Canon T90 (1986) Canon T60 (1990)