Hello Martin,
I work with bot the EX cam and the Kona 3 and my first inclination would be to let the Kona do the down-convert. I have never tested this work flow (down-convert on input) but this would be the first thing I would try. Try a small test (both ways) and see which one looks better, my money would be on the Kona.
One caution… I have captured HD/SDI direct from my EX camera only one time, just recently, and it was only then that I found that even though I shot 1080/24p(23.98) on my EX the HD/SDI output was 29.97! I could not find an option to output 23.98. But unless you are shooting @24 this should not be an issue for you.
I am sure once you try about 30 seconds of both work flows you will be able to make a decision on the best for your purposes.
Good Luck. Let us know what you find with your test.
Richard Cooper
FrostLine Productions, LLC
Anchorage, Alaska
http://www.frostlineproductions.com
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