16mm is not as good of quality 35mm, the grain of the film is bigger and you can see it, especially if a shot isnt exposed properly. As for HD if by that you mean digital obvisouly there is a difference in resolution but the main difference is in the quality of the picture you will not have as many colors, also it will give you a more clear picture without scratches on the film etc.... and there is no grain to be see.
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Teddy Knape
TeddyKnape@sbcglobal.net