Exporting 720p video from iMovie...Does Prores setting help the quality or degrade it?

Do not use ProRes !

It is there for one specialised purpose . . . to retain quality in a movie you may intend to re-edit in the future assuming you no longer have access to the original media.

For all normal purposes .mp4/H.264 is the way to go and gives top quality.

Theoretically ProRes will give better quality but we are talking about microscopic differences which I can guarantee you will never notice.

The choice of Low, Medium and High is also misleading as it simply refers to bit rate.

The only time bit rate matters is when there is motion in an image.

If the bit rate is too low, you will get those unpleasant digital artefacts during movement or transitions.

The Low setting will give very small file sizes and top quality in a video consisting of little or slow movement.

It is not an exact science, you have to use trial and error or experience.

To be safe, just choose High and you will get the best quality available but you may get a file that is slightly larger than necessary.

DO NOT USE PRO_RES!

If TVs improve the videos won't look any better . . . the imperfections will just be more noticeable!

Always keep the files at the resolution they were shot.

There is no advantage in increasing the resolution to 1080p in spite of what some misguided people may claim.

It doesn't improve the quality . . . if anything, the reverse and you end up with unnecessarily large files.

One thing I have discovered about saving things for posterity is that family members couldn't care less and all our efforts will probably be a complete waste of time.

It was only after my parents died and I had retired that I started being interested in the family history and then it was too late. So many questions I should have asked . . .

I inherited around 200 photographs (real ones you can hold!) but quite a few were of unknown people and nobody had bothered to write names or dates on them.

What on earth will happen with the present generation when that number of photos can be shot every day, I do not know. Where will they store all that garbage or will it simply be deleted?