I captured the footage shot by Z1 to computer. The file size is about 11.3GB for one hour footage. The data rate of HDV is 25mbps. So the following calculation shows how 11.3GB comes from:

25mbps x 60 seconds = 1500 mbit per minute
1500mbps x 60 minutes = 90,000 mbit per hour

8 bits = 1 byte

so 90,000 mbit / 8 = 11,250 MB per hour which is 11.25GB

When I examine the data rate of miniDV, it is also 25mbps. My experience with my Sony 3CCD DV camcoder is the file size of one hour footage in computer is 13GB! I don't understand how it calculates. Someone suggests that 3.6MB x 60(seconds) x 60 (minutes) = 1,296MB.

If the date rates of miniDV and HDV are the same, that is 25mbps, the file sizes in computer should be equal.

Could you help me to clarify the above calculation?

It's content-dependent. How much is going on in there?

Should be the same... is the MPEG-2 footage somehow writing the audio to a separate file when you capture? That might account for the space difference...