Diaphragm placement

[badler]

Typically the diaphragm for the aperture is between the front and rear elements. Is there a reason it can’t be in front of the lens or behind?

Thanks

[Dan Fromm]

It depends on the lens' design. Some lenses have the diaphragm in front of the glass, for example the meniscus lenses used in low-end Kodak folders. Some have the diaphragm behind the glasses, for example the 200/4 MicroNikkor AIS.

[Jim Jones]

Changing the position of many lenses from that specified by the optical designers in some cases can cause much deterioration of the image. As for the old Kodaks with a simple meniscus lens, the concave lens surface faces the diaphragm whether the lens is either in front of or behind the diaphragm. Having the diaphragm in front of the lens lengthened the camera, but improved image quality.

[maltfalc]

look through a lens from different angles and see what happens to the aperture.

[Vaidotas]

Diaphragm put in that manner will induce vignetting, at least.