Technical Definitions - VHS vs. DVD

VHS is an analogue videotape format made by a collection of Japanese electronic manufacturers in the early 1980's. In order for the consumer to afford this the standards for NTSC standard broadcast quality video was severely compromised. Luminance bandwidth was cut in half making the resolution detail a mere 220 lines. Broadcast quality recorders at that time could record only up to 450 lines of resolution (Over the air broadcast delivery only gets around 330 lines of resolution viewed at home). In order to fit the color information on the VHS tape, it was cut down to a meagre 20% of the original detail, so there's only approximately 40 lines of color information per horizontal line. Using modern Hi-Fi VCR, you can reproduce Stereo and with some models of Virtual Surround sound. It's close to what you get in the movie theatre?

DVD - Digital Versatile Disc, is mostly used as Digital Video Disc now- it looks like a CD and uses similar data storage technology: image data is recorded as microscopic pits on a reflective surface, except the pits are far smaller and more densely packed than on CD's. Information is recorded as an MPEG-2 highly compressed component digital video signal. Compression rates are about 40 to 1 but the use of careful quality control during the mastering process can usually preserve a lot of the original picture quality in the MPEG-2 data. There's over 480 lines of luminance detail and over 220 lines of color information per line. This is considerably better than VHS or even LD. Although the size of a CD and DVD is the same, up to 4.5 GigaBytes can be stored on DVD (vs. 650 Megabytes on CD).