The foam shouldn't be an issue on a turret model since IR is not enclosed or sharing same space with camera like those on bullet or dome.
i disagree. even a turret lens needs to be sealed off from internal reflections.
improperly fitted ring will let light in from the side that normally will not get in, like from an internal LED.
in the daytime, it's not enuf to cause a problem, but at night, the internal reflection from that LED is enuf to cause the halo.
these super-low-light cams are especially sensitive to such light polution.
and right, the ring does not move when the lens moves to zoom, as the lens is inside a fixed sleeve and the foam/rubber ring is supposed
to keep that sleeve sealed off from the rest of the assembly