Conversion 16mm/35mm

[C.K.]

Simple question:
A friend of mine tells me that:
"when in 2K mode, a 20mm lens given for 35mm camera is equivalent term of field of view to a 20mm lens given for 16mm cameras"

Is this statement true?
If not, how does the 16mm lens convert to 35mm lens ?

Not sure I'm making myself clear...

[David Mullen ASC]

To make the math simpler, just assume 16mm is half the width of Academy 35mm, so a 20mm lens has twice the view on a 35mm camera (or RED in 4K mode) than on a 16mm camera (or RED in 2K mode.)

So if you want to maintain the same field of view when switching to 16mm or 2K cropped mode, you'd have to use a lens with half the focal length, i.e. switch from a 20mm lens to a 10mm lens.

By the way, not all lenses made for 16mm cameras will cover the 35mm frame, whereas all lenses that cover 35mm will also cover 16mm.