Quick question

If I use lets say 80mm lens on 35mm camera and set it to f2.8 (this is just example)
and on a 16mm camera I use the 80mm 16mm lens and set it agian to f2.8

what is going to be a difference in the frame? do I get same picture or is one wider or another, what about DOF? is it going to be the same?

Also can I use 35mm lens on 16mm camera? and if so what is going to be with the frame?

16mm or 35mm just refer to the size of the film print used in millimeters.

well, both I mean if we compare 16mm and 35mm film prints, and in both cases I use the same size lens (but one designed for 16mm film camera, another for 35mm film camera), and set both on same iris, how the pictures are going to be different from each other? in terms of framing and in terms of DOF.

The field of view will be narrower for the 16mm film for a given focal length lens.

thanks, is there a formula to convert this? I mean which s16 lens would match 35mm lens in terms of FOV?

This is based on approximation and not accurate values. Basically for s16, the field of view of an 80mm lens has a roughly similar field of view and angle of view of a 160mm lens on the 35mm format for the same subject-to-camera distance.

You can use the following link for actual calculations:
http://www.panavision.com.au/Information/DOFCalc.htm