Thanks for that. I've downloaded, installed & tried reducing the brightness of the footage captured by Studio but I can only achieve a darker, washed-out image! It looks like you can only adjust contrast during the capture process so I'm going to have to re-capture the footage in Movie Maker & see what it can do.
I really appreciate your help

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Found a useful site
here with lots of Freeware tools & help including editing S/W
here. Not exactly user friendly but it IS free.