Why do small sensor cameras use proportionally larger mounts?

Question

After seeing the Pentax Q which uses a sensor with 5.6X crop factor that is miniature compared to its mount and now the Nikon 1 system with its 2.7X crop factor also looks like its sensor is small compared to the mount, I am curious to know why these mounts are not much smaller?

At the other extreme, compare this to a full-frame model (technically we see the mirror but the sensor is almost the same size) whose mount is not much bigger than the circle it takes to fit the rectangular sensor.

So:

• Why the mounts were not shrunk in proportion to sensor size?
• Is there an advantage in having a bigger mount-to-sensor ratio?

Answer

I'm going to go out on a speculative limb here and suggest a few possible answers:

1. Ergonomics for ILC. If the lens is too small, it's probably not as easy to handle or may be perceived that way.

2. Optics. For handling wider apertures at longer focal lengths, you probably can only make the lens diameter so small and still make it practical for production costs and retail price.

3. Adaptations. So, if there is an adapter (in the case of the Q, from K to Q), then the larger opening may reduce or eliminate the need for optical correction in the adapter or even make it possible.

It may be some combination of all those as well, or none at all. I'm speculating. :)

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