[christopher pupillo] "... there is no magic combination of lens/adapter/DOF attachment that could bring both a servo zoom and prime lens to a lower cost camera like the AF100?"
They're not magic, and I don't know how well they work, but there are solutions out there (kinda). Some examples:
Geared lever:
http://dfocussystem.com/dzoom.php
Non-geared lever:
http://panasonic.net/avc/lumix/systemcamera/gms/gh2/optional_accessories.ht...
As noted above, best results will be with a parfocal-type lens.
Speaking of the AF100: If you're interested in this cam, you owe it to yourself to also consider the similarly-priced Sony FS100. They are both very good values.
As for DOF adapters, there're reasons why folks mostly abandoned them by the hundreds of thousands in favor of DSLRs. The main reason appears to be convenience, or the lack thereof in using DOF adapters vs. DSLRs and other large sensor cams.
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http://www.peterdv.com 
