I have not idea how to judge where the purple fringe came from but I'm sure
OM 180/2.8 has purple fringe with both film and digital. At the mean time
the pruple fringe can be reduced by stop down the lens even on a digital
sensor.
C.H.Ling
----- Original Message -----
From: "Chuck Norcutt" <chucknorcutt@xxxxxxxxxxxxxxxx>
> Regardless of what you think the lenses are guilty of, what you showed
> on that image is not chromatic aberration. It's not the lenses but
> could be the sensor combined with blown image areas. I don't think
> you're using Canon lenses on the Leica are you? Perhaps you're more
> likely to overexpose the Canon? Rather than complain about the lenses
> or software you need to critically examine some of them as I did that
> one to get to the real cause. It could still be hardware but it's not
> likely the lenses.
>
> Chuck Norcutt
>
>
> On 2/22/2014 5:51 PM, Tina Manley wrote:
>> I just know that I get purple or green or red fringing with the Canon
>> lenses that I never get with any Leica lens. It drives me crazy! I will
>> try your suggestions.
>>
>> Thank you,
>>
>> Tina
>>
>>
>> On Sat, Feb 22, 2014 at 4:38 PM, Chuck Norcutt <
>> chucknorcutt@xxxxxxxxxxxxxxxx> wrote:
>>
>>> I don't think it's chromatic aberration. The "purple defringing" slider
>>> under lens corrections in ACR significantly reduces the saturation of
>>> the purple fringe there but does not eliminate it.
>>>
>>> There are two types of chromatic aberration, axial and transverse and
>>> this image doesn't seem to fit either. Axial CA appears throughout the
>>> image while transverse CA doesn't show in the center but gets gradually
>>> worse the greater the angle off-axis. The only place we see "chroma" in
>>> this image is a small area nearly in the center. Therefore this is not
>>> chroma but "purple fringing". The following is from the Wiki article on
>>> chromatic aberration, the photography section that discusses purple
>>> fringing:
>>> <http://en.wikipedia.org/wiki/Chromatic_aberration#Photography>
>>> -----------------------------------------------------------------------
>>>
>>> The term "purple fringing" is commonly used in photography, although not
>>> all purple fringing can be attributed to chromatic aberration. Similar
>>> colored fringing around highlights may also be caused by lens flare.
>>> Colored fringing around highlights or dark regions may be due to the
>>> receptors for different colors having differing dynamic range or
>>> sensitivity – therefore preserving detail in one or two color channels,
>>> while "blowing out" or failing to register, in the other channel or
>>> channels. On digital cameras, the particular demosaicing algorithm is
>>> likely to affect the apparent degree of this problem. Another cause of
>>> this fringing is chromatic aberration in the very small microlenses used
>>> to collect more light for each CCD pixel; since these lenses are tuned
>>> to correctly focus green light, the incorrect focusing of red and blue
>>> results in purple fringing around highlights. This is a uniform problem
>>> across the frame, and is more of a problem in CCDs with a very small
>>> pixel pitch such as those used in compact cameras. Some cameras, such as
>>> the Panasonic Lumix series and newer Nikon and Sony DSLRs, feature a
>>> processing step specifically designed to remove it.
>>>
>>> On photographs taken using a digital camera, very small highlights may
>>> frequently appear to have chromatic aberration where in fact the effect
>>> is because the highlight image is too small to stimulate all three color
>>> pixels, and so is recorded with an incorrect color. This may not occur
>>> with all types of digital camera sensor. Again, the de-mosaicing
>>> algorithm may affect the apparent degree of the problem.
>>> ------------------------------------------------------------------------
>>>
>>> Note especially the discussion about about purple fringing around
>>> highlights and especially about blown highlights. The area of fringing
>>> follows much, but not all, of the contour of his light colored cap which
>>> is also in bright sun. This area does not now measure as blown but may
>>> have been before you started processing or perhaps was only blown in the
>>> green channel. Also, looking at his right hand there is a great deal of
>>> motion blur. I suspect that he also moved his head slightly and the
>>> purple fringe area is somehow mixed up with motion blur and blown
>>> highlights. In any case I don't think this is any fault of your lens.
>>> Fixing this is going to take some PS work. I think I'd try a selection
>>> on the fairly uniform purple color followed by desaturation or color
>>> change to match the cap or any of several other possible methods to
>>> cover it up or eliminate it.
>>>
>>> Chuck Norcutt
>>>
>>>
>>>
>>> On 2/22/2014 1:39 PM, Tina Manley wrote:
>>>> The Remove Chromatic Aberration button in LR did not work on this one:
>>>>
>>>> http://www.pbase.com/tinamanley/image/154578993
>>>>
>>>> It has done a remarkable job on most of the awful CA from the Canon
>>> wides,
>>>> but it barely touched the purple fringe on his cap. UGH!
>>>>
>>>> Tina
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>>>
>>>
>>
>>
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