We've all seen new TV shows available in HD. We've also seen very old shows converted to HD, though some have black bars on the sides (known as pillar boxing) since they weren't shot in a widescreen format.

The question is, why can all that really old stuff be be converted to HD, while stuff from the 70's and 80's often can't? Isn't the newer stuff better?

With TV, normally newer stuff looks better as far as image quality. However, the the 70's, there was a revolution in TV known as the introduction of video tape. While video made editing shows a lot faster and cheaper, it meant many shows were no longer being edited on film. Some were not even shot on film, meaning the whole process took place on video tape.

This made television production much cheaper and much quicker to crank out episodes. At the time, no one really thought these shows would be in demand all these years later.

The problem is, video tape from even 10 years ago wasn't very good and it certainly wasn't high definition. Tape from the 70's and 80's was even worse. Not only was the resolution poor, but over the years many of those tapes have degraded quite a bit. Video tape is not a good storage medium since the magnetic particles on video tape tend to shift and degrade the image over a matter of even a few years. Newer stock (especially digital tape) has improved on this problem, but tape is still magnetic and simply doesn't last.

Film, on the other hand, is much more stable if stored properly. Black and white film is even better than color. The reason for this is the dyes in color film are usually the first to degrade. The silver base of film lasts a lot longer, so older black and white films with no color dyes tend to look better than some color films shot later. Of course film isn't indestructable. Improper storage can destroy film and even after the developing process is finished, the the light-sensitive properties of film continue to work. Properly stored, though, film will outlast almost any analog tape stock.

Since many very old shows (such as "I Love Lucy" and its spinoffs) were both shot and edited on film, the images contain enough resolution to be cross-converted to HD video. They won't be widescreen unless they are cropped, though. Of course, this only applies to shows that were actually edited prior to broadcast. Shows that used kinescopes (essentially filming the on set action off a TV screen), offer very poor image quality. For this reason, shows (like the Honeymooners) that used this process won't ever get the HD treatment.

Some more recent shows with great resale value (such as Seinfeld), are being re-edited from the original film footage for HD. These shows were originally edited on tape, so each scene must be re-constructed from scratch from the raw film footage.