I think a useful term is "circle of confusion". http://fslashd.com/2015/04/circles-of-confusion/ http://fslashd.com/2015/04/circles-of-confusion/ http://www.v

I think a useful term is "circle of confusion". http://fslashd.com/2015/04/circles-of-confusion/ http://fslashd.com/2015/04/circles-of-confusion/ http://www.villageinframe.com/how-big-should-the-hole-be-in-a-pinhole-projector http://www.villageinframe.com/how-big-should-the-hole-be-in-... This is a useful image. https://qph.fs.quoracdn.net/main-qimg-e92438d691243116d52f9945c3fdff17 https://qph.fs.quoracdn.net/main-qimg-e92438d691243116d52f99...