For a camera it's a diaphragm that governs the amount of incoming light.

相机通过改变光圈的大小来控制曝光度
Even they're both encased in black.

它们甚至都有暗室
The light-sensitive part of the eye

眼睛和相机的感光部分
and part of the camera are both encased in black.

都被包在暗处
The difference is--So in fact,

区别在于事实上
the eye and a camera look a lot alike

眼睛和相机看上去非常像
and we know the camera is an artifact.

我们知道相机是人造品
The camera has been constructed by an intelligent--

相机是由有智慧的人
by intelligent beings to fulfill a purpose.

为达成某种目的而制造出来的
In fact, if there's any difference between things like the eye

事实上如果要说眼睛
and things like a camera,

和相机有什么区别的话
the difference is that things like the eye

那就是眼睛