What difference is there between CIF, HALF D1 and D1 resolutions?

The essential difference lies in the resolution:

- CIF: 320x288 PAL / 320x240 NTSC
- HALF D1: 720x288 PAL / 720x240 NTSC
- D1: 720x576 PAL / 720x480 NTSC

By analysing these data against video quality (which can be low, normal, high or very high), we can determine how much space in kB a video frame occupies on a HDD.
CIF ranges from 1.8 kB with low quality to 6 kB with very high quality
HALF D1 ranges from 3.6 kB with low quality to 12 kB with very high quality
D1 ranges from 7.2 kB with low quality to 24 kB with very high quality

From these figures it is a simple matter to calculate how much space is occupied by recordings made by a camera operating in real time, i.e. at 25 Fps for an hour of recording.

For example:
CIF format, High quality = 6 kB 1 Frame
6 x 25 Frame = 150 kb per Sec
150 x 60 = 9000 Kb per minute
9000 x 60 = 540,000 Kb per hour
540,000 : 1024 = 527.35 MB

1 MB = 1024 KB.
Likewise, 1 GB is equivalent to 1024 MB and 1 KB to 1024 byte. 1 byte is equivalent to 8 bit.