Aperture stop for an optical system

[fog37]

Hello Forum,

The aperture stop (AS) of an optical system is that physical aperture in the system that limits the amount of light from the object.
Consider a 2D object formed by point objects. The AS is determined by considering the object point that is located on the optical axis. Will the AS for that on-axis point also represent the AS for all the other off-axis objet points forming the object?

If the same 2D object moves to a different position along the optical axis, the AS will change since it is determined by the on-axis object point and its location, correct?

If that is correct, it seems that the AS is not fixed aperture for the optical system but strongly depends on the position of the 3D object being imaged...

Thanks,
fog37

 

[davenn]

If the same 2D object moves to a different position along the optical axis, the AS will change since it is determined by the on-axis object point and its location, correct?

not sure how you come to that conclusion. If I set a f2.8 aperture on my camera lens. it stays at f2.8 regardless of how far or close an object is to the lens or whether it in the axis line of the lens or off to one side of that axis

If that is correct, it seems that the AS is not fixed aperture for the optical system but strongly depends on the position of the 3D object being imaged...

refer to my previous comment

cheers
Dave