Help with Math

[Michael Barosky]

Currently shooting with a super 35 format lens. (Mitakon Speedmaster 35mm) on my Komodo. Looking to upgrade to a Zeiss CP Prime which is Full Frame. To get a similar field of view would I choose the same 35mm focal length or would I need a wider, perhaps 25mm?

 

[Phil Holland]

You would choose a 35mm lens as it would be the same approximate field of view with the only subtle differences coming from the different lens design.

In this case, you'll get more rounded bokeh by going to the CP prime designed for the larger format.

 

[M Harvey]

Same focal length.

There is no difference in the field of view of a lens designed for super 35 and a lens designed for full frame 35. The only difference is that the FF 35 lens has more coverage—the circle of illumination it projects is larger to cover a larger sensor. (And if you did the reverse and put the super 35 lens on a full frame camera, it would also show the same field of view. It just might not fully cover the sensor, and therefore have a hard vignette or get soft at the edges.)

This is what people mean when they say (for a 50mm lens), “a 50 is a 50 is a 50.”

 

[Michael Barosky]

Thanks to both of you!