Unlike older SLR systems, Four Thirds has been designed from the ground up
to be entirely digital. Many lenses are extensively computerized, to the
point that Olympus offersfirmware
<http://en.wikipedia.org/wiki/Firmware> updates
for many of them. Lens design has been tailored to the requirements of
digital sensors, *most notably through telecentric
<http://en.wikipedia.org/wiki/Telecentric_lens> designs*. The size of the
sensor is significantly smaller than for most DSLRs and this implies that
lenses, especially telephoto lenses, can be smaller. For example, a Four
Thirds lens with a 300 mm focal length
17.3mm x 13mm , diagonal = 21.6mm .. flange focal distance = 38.67 mm.
This means the angle of convergence / divergence is closer to 30 degrees
than the 60 degrees of many 35m camera systems. Still no closer to parallel
really, the light is still convergent.
" near telecentric construction " is marketing talk. Not unlike a
politician saying he nearly kept his promise. He did or he didn't. A
lens is telecentric or it isn't - you have malaria or you don't.. Saying
they chose to put the lens on their camera further from the film plane than
some other makers and *almost as far* as some 35mm film cameras is really..
well, weak. Heck, this would suggest a standard K mount lens is even
*more* telecentric (it's not) as it's registration distance is even greater
