1. What's a image file?
(>) A image file is a CD/DVD, but instead of insert it into your CD/DVD-Rom, you open it from inside your Hard Disk. So, it's a file that replaces a normal CD/DVD. Inside the image are the CD/DVD files like if it were a CD/DVD.
A cam is a theater rip usually done with a digital video camera. A mini tripod is sometimes used, but a lot of the time this wont be possible, so the camera make shake. Also seating placement isn't always idle, and it might be filmed from an angle. If cropped properly, this is hard to tell unless there's text on the screen, but a lot of times these are left with triangular borders on the top and bottom of the screen. Sound is taken from the onboard microphone of the camera, and especially in comedies, laughter can often be heard during the film. Due to these factors picture and sound quality are usually quite poor, but sometimes we're lucky, and the theater will be fairly empty and a fairly clear signal will be heard.
Knowing your data will be there when you go back to it days, months, or even years later--well, that's a bit harder. Not all discs are created equal, as Fred Byers, information technology specialist at the National Institute of Standards and Technology, can attest.
Byers is part of a team heading up an independent study of DVD media quality. Based on the first wave of testing results, the situation is murky at best.