I'm taking the same kit as I did to Antarctica last year. 5dm2, 40d, 17-40, 70-200/f2.8 is, 100-400, zenitar 16mm, rode videomic, 580ex ii, laptop with 2 usb drives for backup, handful of extreme iii/iv CF, manfrotto 190mf3 with acratech ultimate ballhead. All stuffed in a Burton Zoom 28l photo backpack. New this year are a 24-70, Panasonic LX3, Gopro HD helmet cam and a F-Stop Santori or Tilopa photo backpack.
The only time I used my flash was aboard the ship for some people shots, I felt that the wildlife was harassed enough with the presence of people and didn't want to light them up too.
I wasn't too cautious about condensation when bringing gear back aboard the ship, just left it in the backpack after taking out the CF cards.
40F doesn't sound too cold but it does get chilly while cruising on the zodiac rafts. I'm bringing North Face ski pants and a ski jacket shell, all synthetic lightweight shirts/long johns, fleece pullover/gloves and a balacava.
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