The purple fringing, or similar problems, are common to a great many digital cameras to various degrees. However, in all the examples which I have encountered, that particular phenomenon is always associated with areas of high contrast - particularly with the transition between dark regions and brightly lit areas at sharp edge and especially with high intensity bright spots. There are no edges in these shots at all, so I do not think that particular problem has anything to do with it.
Your comment about software is an interesting one. Certainly my problem does follow the camera, not the scene, so lens and sensor are candidates - but you are right in that the software does process the image data the same way, no matter which way the camera is oriented. I would expect software, though, to have a consistent effect across the image - or at least one with some (hopefully observable) pattern.
Still, some tests were in order.
Parameters which I varied:
- Image size
- Image quality
- Zoom level
- Flash on/off
- White balance
and I also took a shot in RAW format.
To summarise, ALL images showed the same basic reddish discolouration in the left and lower left, and on the right to a lesser degree. This includes the RAW image.
Varying the image size and quality did show something interesting ... there were some combinations which made the problem less noticeable than others, but it was always there. This would indicate the software is not being consistent in its processing.
Another observation is that on all images under extreme saturation, there was a quite obvious pair of 'train tracks' running up alongside the right edge. These look to me like the sort of 'edge' irregularities you might get in chip manufacture. The same thought crossed my mind about the circular shape of my main problem - reminiscent of the shallow puddle that forms in the gentle dip of a 'flat' piece of concrete.
Will try some more tests .. and then look at the firmware update, followed by some more testing.