Paul Antico sent this email to Canon Tech Support:
It seems many are having the issue; everyone who tries to re-create it can. If you take one of your C300 cameras, and aim it at high contrast situation such as a window (try to recreate the shot I sent you as an example), then overexpose over 100 IRE the window itself, and move the camera so that there is an angle of some sort, you will see it too.and received this reply:
Another test is to aim the camera at branches of a tree, but such that the sky is over-exposed past 100 IRE. The branches will show pink and purple fringing not related to the lens, especially on horizontals and angles.
I think it's likely an error in processing when the highlights are concerned. Sony's FS100 does it as well, albeit much more harshly. That said, if one properly exposes the highlights the issue does go away. I didn't notice the problem until I specifically tried to create it. I normally don't let the highlights clip because, well, that's the wrong thing to do.
The concern is when transient clipped highlights happen in areas of horizontal or angular contrast junctions. For example, a window, glints of sunlight off water, etc. Basically difficult to plan for clipped whites. If there is any strong contrast in the vicinity, the camera may bloom or show chroma aliasing as green/purple blocks.
Thanks for following up with us.
I took a look at those forum posts, and I can see how that would be distracting. The cyan/purple fringing seems to be more notable when the shooter is deliberately trying to blow out the highlights. Keep in mind that the camera has 12 stops of latitude, which goes beyond what many cameras can do, plus it has 3 built-in ND filters that can cut down in the light coming into the camera, so this seems to be a situation that can be avoided by adjusting the settings accordingly. Still, it is something that I will pass along to our senior engineers. We will investigate the situation, and see if there is anything else that can be done to reduce the fringing.
I hope this information is helpful to you. Please let us know if we can be of any further assistance with your Canon equipment. Thank you for choosing Canon.
Canon Technical Support Representative