Not sure if this is a valid question to ask. I am trying to determine an adequate storage capacity for a back-up portable HD. I use a Canon 400D & a Canon G11 to shoot RAW. Although the size of RAW files can vary, is there any basic rule-of-thumb regarding the average RAW file size? If so, I can get a rough estimate of the storage capacity I will need to back up my CF/SD cards.
Check the size of the entire folder of your existing RAWs on your HDD, divide by # of RAWs.
Alternatively, I believe DPReview gives RAW sizes in their camera reviews, and I'm sure some other reviews.