Some mirrorless options for Pentax

Started Aug 25, 2018 | Discussions thread
Barry Pearson
OP Barry Pearson Veteran Member • Posts: 8,723
Re: Mounts matter; cameras come and go

Mark Ransom wrote:

The only reason for doing a new mount is if it brings some substantial advantages over an old one.

Yes, substantial. Both in photographic capability and return on investment. Now and/or in the future.

For mirrorless, the obvious advantage is to allow a shorter registration distance. But it's not strictly necessary; Pentax had a prototype lens for the K-01 that extended behind the mount into where the mirror box would ordinarily go. They never brought it to market.

I too query the need for a shorter registration distance. The point about extending into the body beyond the mount is a good one.

Here are some sizes that may be relevant. First for the D FA* 50mm f/1.4 lens, then for the Laowa 12mm f/2.8 ZeroD, then for the Samyang 12mm f/2.8 Fisheye.

D FA* 50mm f/1.4

The tube containing its rear elements, that slides in and out for focusing, has an outer diameter of about 35mm. So that is the space available (in that version of the K-mount) after the essential features of the mount have been fitted.

The rear element of that lens is about 30mm across, and is (slightly) within the body of the camera when the lens is focused at infinity.

D FA* 50mm f/1.4, focused at infinity. (Centimeters).

Laowa 12mm f/2.8 ZeroD

The rear element is smaller than the rear element of the 50mm f/1.4.

The front element is large. I suspect this applies to any FF 12mm f/2.8 lens.

What would be the equivalent sizes for a 12mm f/2.8 minimum distortion lens designed to exploit lack of a mirror? Could the rear end of the lens fit within the tube size used by the 50mm f/1.4 lens?

Laowa 12mm f/2.8 ZeroD, K-mount. (Centimeters)

Laowa 12mm f/2.8 ZeroD, K-mount. (Centimeters)

Samyang 12mm f/2.8 Fisheye

The rear element is smaller than the rear element of the 50mm f/1.4.

The front element is very large. I suspect this applies to any FF 12mm f/2.8 fisheye lens.

What would be the equivalent sizes for a 12mm f/2.8 fisheye lens designed to exploit lack of a mirror? Could the rear end of the lens fit within the tube size used by the 50mm f/1.4 lens?

Samyang 12mm f/2.8 Fisheye, K-mount. (Centimeters).

Samyang 12mm f/2.8 Fisheye, K-mount. (Centimeters).

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