Effective focal length of anamorphic lenses on different sensors

[Alex Birrell]

Hi everyone,

 

I've been trying to find information online about the effective focal length of anamorphic lenses on cameras that crop their sensors to allow 2x anamorphic. For example, the selling point of the Alexa 4:3 is that a 40mm anamorphic lens will give the same field of view as it would on 35mm with an anamorphic gate.

 

If this lens were used on a Sony F55 or Red Epic (which window box the Super 35 sensor) what would be the "effective" focal length?

 

I know the 40mm remains a 40mm but would it become more of the equivalent of a 50mm anamorphic on 4 perf 35 etc.

 

Many thanks!

[David Mullen ASC]

You just have to find out the recorded sensor HEIGHT then multiply by 1.2 to find out the usuable sensor width for a 1.20 : 1 image area with a 2x optical squeeze.

[Alex Birrell]

Thanks!