The mystery of purple fringing (PF) is seriously deep. There are a number of theories and explanations on the Web (none from the camera/lens makers
). Some say that it is simple longitudinal chromatic aberration (CA). Others claim that it is related to incident light angle against the micro-lens array of the camera sensor. I take the empirical approach and simply state that it appears to be an interaction of certain lens designs with the digital sensor technology. I get PF with some of my lenses (77/1.8 Limited (mild) and Zenitar 16/2.8 (not so mild) for example) on the K10D, but not with others. Those same lenses NEVER behave that way on color film.
In fact, I have only seen one example, in over 40 years of photography, of anything that even remotely resembled PF on film and that was with my Olympus XA near the frame margins. I believe that case to be very nasty CA related to the XA's unique lens design.
So regardless of the cause, it is pretty much a fact of life with current digital sensors. When I tested the DA 15/3.5 Limited, it had mild PF. My 18-55 Kit has it at times as well (so much for digital-optimized lenses). With the exception of the lenses mentioned above, the rest of my kit is relatively PF-free.
Steve
Last edited by stevebrot; 04-30-2011 at 01:43 PM.