1/2" vs. 2/3" lens

[mike_va 0]

I've looked around but cannot seem to find the answer to this.

 

If a lens says 6mm 2/3 does that mean it will be have a higher effective focal length (like 8mm) on a 1/2 sensor camera? Or are all CS mount lens ratings referenced to a 1/3" sensor?

 

Thanks in advance

[NotoriousBRK 0]

The differing effective focal length is a factor of different sensor sizes, not lens properties.

 

A lens is rated for the size of the "sweet spot", or area where it achieves a flat focal plane. It's more expensive to make a lens that can focus clearly over a 12" area than a 12 micron area (using extremes to illustrate a point). However the 12" lens would work fine on the 12 micron sensor, it would just be overkill.

 

Same thing for a 2/3" rated lens. It would work fine on a smaller sensor (assuming that it mounts properly, etc.).

[survtech 0]

I've looked around but cannot seem to find the answer to this.

 

If a lens says 6mm 2/3 does that mean it will be have a higher effective focal length (like 8mm) on a 1/2 sensor camera? Or are all CS mount lens ratings referenced to a 1/3" sensor?

 

Thanks in advance

6mm = 6mm = 6mm. The focal length would say the same but the image would appear closer on smaller imagers (6mm = 90+ degree HFOV on a 1" imager, 72 degree HFOV on a 2/3" imager, 56 degree HFOV on a 1/2" imager, etc.)

 

Of course, if you put a lens made for a 1/3" camera on a 1/2" camera, the picture would have a tunnel effect, ie. it wouldn't fill the frame - like looking through a telescope. The opposite is acceptable, though.

[mike_va 0]

Thanks!