When you mount a lens (whether the camera is on or off), the camera interrogates the lens for its characteristics, including maximum aperture, which one of the focusing parameters.

装上镜头后(不论相机是开着还是关闭的)，相机便会获知镜头特征，包括最大光圈，哪一组对焦参数等。

youdao

Surface mount LED lamp. High efficiency red, super bright green. Lens type water clear.

表面贴装LED灯。效率高红，超明亮的绿色。镜头类型，水质清澈。

youdao

Surface mount LED lamp. Super bright green. Lens type water clear.

表面贴装LED灯。超级明亮的绿色。镜头类型的水清除。

youdao

DENVER, CO (September 10, 2012) - PENTAX RICOH IMAGING AMERICAS CORPORATION (PENTAX), today expands on the innovative Q-system with the new 12.4 megapixel PENTAX Q10 interchangeable lens camera, new Q-Mount PENTAX 06 15-45mm F2.8 telephoto zoom lens and Adapter Q for PENTAX K-mount lenses, expanding its family of compact Q series products.

ENGADGET: Pentax launches Q10 interchangeable lens camera, K-5 II and K-5 IIs flagship DSLRs

That may sound impossible, but it apparently works by concentrating the extra light-gathering area of a full-frame lens down to the smaller E-mount sensor area, turning an f4.0 lens into an f2.8 lens, for instance.

ENGADGET

By using this adapter to attach any K-mount lens onto a PENTAX Q series camera, the focal length of the lens is extended by approximately 5.5 times in the 35mm format.

ENGADGET: Pentax launches Q10 interchangeable lens camera, K-5 II and K-5 IIs flagship DSLRs