Canon C300 Does Great in Low Light but White Wall 'Breaks' the 8-Bit Codec
Here's an excellent test/review of the Canon C300 camcorder by Paul Steinberg. He shoots a number of low light shots with the camera but also manages to "break" the 8-bit codec, in his own words. It's hard to make out what is C300 compression and what is internet h.264 compression, but in Paul's words "you can see a ton of quantizing little blocks" -- even when viewed on a TV. No matter how good your 8-bit implementation is... it's still 8 bits. Is this a deal breaker for you?
Deal breaker or not, the C300 also looks to be the best low-light camcorder on the planet. 20,000 ISO is not something most people will be using regularly, but it's there and useable (in some situations). 5,000 ISO looks good, and in practice more people will notice (as a positive) the ISO flexibility than will have a problem with the 8-bit codec. Paul also notes that the camera does not seem to take well to pushing the exposure in post in terms of shadow detail -- don't be afraid to use the higher ISO settings.