On Sun, Sep 13, 2009 at 5:48 AM, Niels Kristian Bech Jensen
<[email protected]> wrote:
>> From: [email protected]
>> To: [email protected]
>> Date: Sat, 12 Sep 2009 18:56:38 +0200
>> Subject: Re: [UFRaw-Devel] AHD interpolation and maze/mosaic artifacts
>>
>> In the following file, it's especially apparent in the grey border of
>> the chart:
>>
>> http://files.pcode.nl/temp/IMG_4500.CR2
>>
>> Using VNG4 completely fixes the issue.
>>
> Thanks for the image file.
>
> I have searched for explanations of the maze effect and it seems to be a
> common problem with AHD interpolation (and similar algorithms). Some people
> suggests that it happens when the green channel is either underexposed or
> clipped - or when the two green channel values are too different to be
> handled as one. Other suggests it is luminance noise being interpolated.
>
> The developers of perfectRAW are working on new interpolation algorithms and
> some code to equilibrate the green channels
> (http://www.ojodigital.com/foro/perfectraw-perfectblend/257378-labyrinth-artefacts-green-equilibration.html).
> You can find their main discussion forum here (much of it is in Spanish
> which is not my main language):
> http://www.ojodigital.com/foro/perfectraw-perfectblend/

They seem to have solved the issue for AHD as well:

  http://img88.imageshack.us/img88/719/patternnoisehj42zu5.jpg

Regards,
Pascal de Bruijn

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