Originally Posted by Abbazz 
I beg to differ. Certain lenses (mostly zooms, but also some prime lenses with many elements) are much more likely to cause purple fringing (call it sensor bloom if you prefer) than others. Lenses with a very contrasty rendering are also more sensitive to this problem.
I think nobody here was talking about chromatic aberrations (I guess this is what "CR" means), which is indeed a different problem.
Cheers!
OK I stand corrected. From Wikipedia lots of potential reasons.
Purple fringing - Wikipedia, the free encyclopedia Other explanations
Purple fringing is usually attributed to
chromatic aberration, although it is not clear that all purple fringing can be explained this way. Other attributed causes of purple fringing include:
- Sensor effects:
- Chromatic aberration in each CCD cell (microlenses)
- Digital noise in dark areas
- Image processing and interpolation artifacts (almost all CCDs require considerable processing)
- Stray ultraviolet light
- Stray infrared light
- Image bloom from overexposure
- Leaks between cells of the CCD