An old school super 8 film has 3600 frames, which at standard speed is played at 18 frames per second
That 3 and a third minutes (3mins 20 sec.)
Now 640x480 is a VGA frame in pixels, at 24 bit colour (8 bits / 256 shades for each red green blue) is about 900k per a frame, uncompressed
That’s under 4GB for 3 minutes 20 seconds for 3600 frames, uncompressed
So one 4GB SD card in almost any digital camera will when set to its lowest resolution equal at least one roll of super 8 film
Add in the fact you will be saving jpg and not bmp and you can divide that by 15
So a 256MB SD card recording VGA resolution images to jpeg is about the same as one roll of 50ft super 8 film