I'm just beginning learning Esperanto, using the materials available on lernu, and I can't clarify the difference between the verbs "regardi" and "spekti".

When might either be used? Is there a difference? Which would be used in relation to TV or film?

Note spelling: rigardi, not regardi.

Spekti would be for watching (a film, TV, etc). It's for watching some ongoing activity, presentation, etc where something is actually happening and you want to follow the progress of it.
You can perhaps remember it by the mnemonic that a spectator would "spekti".
Mi spektis la tutan filmon - I watched the whole film.
Mi spektis la ludon - I watched the game.

Rigardi is for simply literally looking at something, perhaps even very briefly.
Mi rigardis ŝin - I looked at her.
Mi rigardis la horloĝon por ekscii kioma horo estas - I looked at the clock to see what time it was.

If that is the case, then rigardi seems very similar to vidi. Could you clarify the difference between these?

Thanks for your help

Scalex:If that is the case, then rigardi seems very similar to vidi. Could you clarify the difference between these?

Thanks for your help

vidi = see
rigardi = look at

"Vidi" simply happens automatically because your eyes are open and something is in your field of vision.

"Rigardi" is intentional and conscious, focused and directed.

E.g. right now I happen to see (vidi) books on my shelf and papers on my desk, but I'm not looking at (rigardi) them - I'm looking at my computer monitor.

It is the difference of whether you just happen to be perceiving something, or if you are consciously paying attention to it.

There is a similar distinction between hearing something (aŭdi) and listening to something (aŭskulti). E.g. right now I hear cars outside my window, but I'm not really listening to them.

I listen to someone when we're conversing, or to music that I'm interested in, for example.