Compression
The amount of information discarded to 'save' space.

The higher the number the more information is thrown away. Simplistically, as the information is stored digitally, if the sky is blue, why record it every frame, just record the changes. With new technology, the effects are unnoticeable, until you try things like keying, slo-mos, and colour correcting. With highly compressed formats, we have less information to work with.

Formats

*Most DV cameras have a 16:9 mode, but basically shoot a 4:3 picture, and then electronically stretch it. This is not acceptable for many stations. Channel 4 would prefer you to shoot 4:3, and then Arc to 16:9. (see widescreen).

**Calculated by ratio of bitrate to uncompressed digital RGB.

Formats Suitable for Archive
Working on many archive based programmes, it is horrifying to see how from after the sixties the quality of archive footage gets worse.

Film footage can nearly always be re-telecined to look reasonable, but much more recent footage has been badly copied from one format to the next, as formats changed.

Many broadcast programmes for the eighties are almost unusable.

With Compression this will only get worse.

While some formats cleverly throw away bits that seem unnoticeable, if you later transfer these to another different type of compressed format, it will throw away other parts of the signal.

Eventually when this footage gets broadcast with yet another compression, there may be nothing left.

If you intend to make money from archive footage it needs to be on the least compressed format that is sensibly affordable.

This way in the future you will make a fortune as everyone elses footage disappears!