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Message: <blockquote data-quote="ostling41" data-source="post: 1371278" data-attributes="member: 62109">The entrance pupil in a complex lens may be further aft than the front lens element.  In the case of the G9 it is quite evident that the entrance pupil retracts during the zooming, while the outermost lens element goes out -- you can see it happening. The entrance pupil is a lot more obvious if you can take the lens off the camera, and hold it up to the light. You can't do this on the G9, but you can still see the smallest diameter of what is covering the sensor. That is the entrance pupil. You'll see this on whatever digital compact you own. You can see the exit pupil of a lens, too. For example, hold up a pair of binoculars, and look at the eyepiece. That small bright spot is the exit pupil --  it will be much smaller than the diameter of the eyepiece lens, and typically at an axial distance not coincident with the outermost glass surface.</blockquote>