If it's recording fast, it covers most of the tape in less time. If it records slow, it uses as much of the tape in longer time. To get the best quality picture, recording on SP mode is suggested. The slower the speed of a recording the more crammed up the information is on one single tape, and the worse the quality of the image. But nevertheless, many find it very convenient to be able to fit six hours or more on one single T-120 tape.
Videotapes have the ability to hold a specific amount of recorded material on different speeds.
Here is a simple chart with tape types, and speeds and how much recorded material they can hold in minutes. More technically, it refers to the actual makeup of the metallics in videotape which effects sensitivity. A higher-grade tape is more sensitive to detail, and while it picture quality may not be noticeable from one look, in the long run, the difference is obvious less noise. Standard grade videotape is good enough for any VCR or camcorder. Other grades include high grade and extra high grade.