[mark_element]

A note, why do they use such small sensors (11mm) rather than the large sensors in full-frame DSLRs (42 mm)?

Didn't quite get that constraint as being absolutely necessary.

[mozumder]

Smaller sensors mean bigger depth-of-field.

Shallow depth-of-field is incredibly distracting for video and difficult to work with. Everything is out of focus. It's mostly a photography/art thing to isolate your subject.

You can see how sports program would want everything to be in focus, instead of just one player. That would look ridiculous.

[alfanick]

this + Smaller sensor means larger effective focal length, which tends to smaller/cheaper lenses.

86x zoom for 35mm sensor would be much larger (so big that it would be impractical), heavier and much pricier than $200k.

[wmf]

Mostly for legacy compatibility, but the lenses would need to be even larger to cover a larger sensor.