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
>> --
>> _________________________________________________________________
>> Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
>> Archives: http://lists.thomasclausen.net/mailman/private/olympus/
>> Themed Olympus Photo Exhibition: http://www.tope.nl/
>>
>>
>>
>
>
--
_________________________________________________________________
Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
Archives: http://lists.thomasclausen.net/mailman/private/olympus/
Themed Olympus Photo Exhibition: http://www.tope.nl/
|