P.J. Are you are on the fringe and turning purple?
Then it's the right cure! ;-)
Now, seriously:
I didn't have a chance to listen to the video Rob posted (I am at a
conference all day today).
I think the explanation that you referenced/mentioned in the other message
makes sense. Your situation with multi-pixel fringing is indeed puzzling.
I wonder if it is somehow related to how the optics coating is done.
Here is my guess based on the knowledge of physics of optics.
And, sorry, it is still somewhat vague, as I don't have a complete
scenario.
Typically, the antireflection (AR) coating is tuned to a particular
wavelength, or a set of those, not the entire spectrum. AFAIK, it is the
centered in the yellow-green part of the spectrum, which is where the
majority of the daylight is. (That's the reason why you see purple
reflection when your look at the lense.)
Now, that can change the balance between the amount of light that comes
through that lense in the yellow-green part of the spectrum relative
to that in red and blue parts of the spectrum. This would in turn
contribute to the disbalance due to what you described about the
compensation/balance between the green and red-blue pixels.
This may explain why certain lenses are more prone to this effect than
others, - due to the difference in the AR coating.
Now, why can it be several pixels wide? I am guessing that in some cases,
the edge of the image feature is more than one (more exactly four in the
Bayer pattern) pixel wide. And if the contrast is high, it means that
there is a high light intensity gradient that happens over several pixels.
(You don't need to have highlights blown out, just a disbalance.)
Hence, the multi-pixel purple fringing.
If my guess is right, how this effect shows should depend on the object
boundaries (broad or narrow, relative to the magnification [read: pixel
size]) and the lighting condition (light contrast).
I am looking forward to listening tonight to the video's explanation.
Igor
Mon Oct 6 23:01:28 EDT 2014
P.J. Alling wrote:
It's nothing that a couple of aspirin and a shot of whiskey won't cure...
Really not a problem at all...
On 10/6/2014 8:23 PM, Rob Studdert wrote:
PJ has a purple fringing problem? How unfortunate :(
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