Zack Matush has about 50 of them, and film and video lecturer Rod Bingaman has twice that.

They're DVDs -- digital videodiscs most people are familiar with, that feature full-length commercial motion pictures, additional material such as outtakes, commentary from actors, director's notes and movie trailers.

Matush (senior-math) prefers DVDs to VHS tapes because they have a better picture and better overall quality.

"People collect them," Bingaman said. "I have 100 or so [DVDs] on my shelf."

How a DVD made

Bill Kelly, head of the integrative arts department, said DVDs contain many layers of plastic.

The layers include a protective polycarbon layer and inner layers made of gold and aluminum, which make the discs colorful when they are spun.

Each disc contains microscopic bumps arranged as a single, continuous and extremely long spiral track of data.

The bumps hold the information on the DVD.

The information is extracted from binary codes of zeros and ones that are burned onto each disc by a laser, said Michael Schomer, an audio and video technician.

Zeros and ones determine the picture and audio that go on the DVD, Schomer said.

The information is formatted and stored in the disc, he added.

It has to be encoded and compressed to go on the DVD, Bingaman said.

DVD manufacturers use a code scheme that looks at the image and saves space for information with movement or a lot of detail, he added.

A movie with fewer colors will save space for scenes or menus with more colors and detail, Bingaman said.

"All of the various encoded messages are formed through computers," Maura Shea, senior lecturer of film and video, said.

"Computer stuff makes it work."

A professional DVD can cost thousands of dollars to produce, but there are software programs made for home use that cost around $500.

"Home software has pretty decent quality," Bingaman said.

How a DVD is read

Once the disc is manufactured and bought, it is viewed on a DVD player.

All players read the disc's information using a laser, which reads the microscopic bumps as the disc spins, Kelly said.

Pirated DVDs

While professionally produced DVDs are not usually problematic to play, pirated DVDs, which are increasing in popularity, may be difficult to play on DVD players.

All computers can play the pirated discs, but some commercial players don't recognize all codecs, Bingaman said.

"Pirated DVDs are made on different file types," Shea said.

"Computers can read anything, but not all DVD players can read all file types."

Most new DVD players will read pirated DVDs, Bingaman said.

DVD vs. VHS

"DVDs have the purest quality," Schomer said. "The DVD reads the zeros and ones and pulls back exactly what was written. There is no distortion of the signal. Plus, resolution isn't as high on a VHS tape."

DVDs store the information digitally. They can store 500 full lines, as opposed to VHS tapes, which can only store about half of that, Bingaman said. A DVD can hold up to eight gigabytes.

"VHS has line resolution and loses information in the scan," Bingaman said.

With a VHS, as it is watched more times, the image will degrade and the tape will start to wear. The magnetic tape in the VHS gets distorted after a while.

"Tapes are mechanical and can break ... DVDs don't break easily," Kelly said.

Shea added that commercial DVDs can hold bigger image files. Bingaman said he expects a better-quality DVD will be produced within the next five years.

With the quality of DVDs increasing, the demand for VHS tapes continually decreases.

"Stores are trying to phase out VHS tapes," Shea said. "I was trying to get a tape that isn't available on DVD, and nobody in town had it."

Although DVDs are popular, they do have some downsides.

"DVDs are made of natural materials and will eventually degrade over time," Kelly said. "We don't know the use life of DVDs yet."

Bingaman said he thinks that, eventually, video on demand will become more common than DVDs. He added that he thinks people will record movies off of video on demand and onto a DVD.

Kelly also said the technology will eventually change.

"Eventually, costs of DVDs will come down," Kelly said. "Ultimately, DVDs will be replaced by networks. We'll have the ability to access any movie ever made."