10-04-2021, 03:13 PM
PF was dealt with by Sigma (at least) by applying a coating to the back element. They called this "DG" (that, and the upgrade of the electronics for EF, was the only difference between DG and non-DG lenses).
PF is related to the amount of light, it is not a chromatic aberration from the optics of the lens. My understanding is that it has to do with the amount of (UV?) light that hits the sensor, gets reflected back to the lens, and ends up back at the sensor again, gives this PF (purple, magenta, blue depending on camera/lens) fringe.
You don't see it with just "contrast", but at the edge of strongly exposed/over exposed areas (see the sample image Klaus provided as example).
PF is related to the amount of light, it is not a chromatic aberration from the optics of the lens. My understanding is that it has to do with the amount of (UV?) light that hits the sensor, gets reflected back to the lens, and ends up back at the sensor again, gives this PF (purple, magenta, blue depending on camera/lens) fringe.
You don't see it with just "contrast", but at the edge of strongly exposed/over exposed areas (see the sample image Klaus provided as example).