Re: CororChecker SG CIE reference values (or lack of)
Re: CororChecker SG CIE reference values (or lack of)
- Subject: Re: CororChecker SG CIE reference values (or lack of)
- From: Robin Myers <email@hidden>
- Date: Fri, 18 Dec 2009 01:08:28 -0800
That should read "Until recently I used the Mini Classic ..." in paragraph 6, line 2.
Sorry for the omission.
Robin Myers
On Dec 18, 2009, at 1:04 AM, Robin Myers wrote:
> There are always tolerances in the manufacturing process, ColorCheckers, any of the family, have them too.
>
> There are two major reasons why you should measure your own chart; reformulation over the years, and manufacturing tolerances. Depending on the patch, a small tolerance could be insignificant, or huge, depending on the patch. Some of the ColorChecker Classic patches have been reformulated over the years, by my count at least 4 times, including the 4 patches I noted has having changed in the ColorChecker Passport.
>
> As for the number of colorants used, I never wrote that the ColorChecker Classic uses more pigments than the ColorChecker SG. Both of these two charts are made by the same division of X-Rite from the pigments used to make the Munsell Book of Color. So I suspect they have overlapping sets of colorants. Only those working in X-Rite's Munsell Color division would know the exact amount.
>
> There was an article several years ago where the authors used Principle Component Analysis to reduce the Munsell Book of Color to a set of theoretical basis pigments. If I remember correctly, the authors concluded that it took from 8 to 11 theoretical pigments to make the Book of Color. I was told by someone at X-Rite that the actual number was higher.
>
> As for the usefulness of the Classic over the SG, I wrote an article a few years ago where my tests showed that the average color error for a camera profile using the SG is about half that of using the Classic.
>
> The SG is the better chart if you can afford it and if you are using it in the studio; the semigloss surface may require careful reflection control only available in the studio and the chart's size is not very handy for field work. Until recently I used the Classic for my field work because of its convenient size and matte surface. The Passport, with its protective plastic case and extra neutral patches, is now my choice for field work.
>
> Robin Myers
>
>
> On Dec 18, 2009, at 12:23 AM, edmund ronald wrote:
>
>> I beg to differ. Colorcheckers have been known to vary considerably,
>> the only way to really know what one has is to dig out a spectro and
>> measure.
>> BTW, weren't you the one, Robin, who said that the original
>> Colorchecker is actually more useful than the SG because it is based
>> on more pigments? I wonder how many base pigments are used for the
>> Passport?
>>
>> Edmund
>>
>>
>> On Fri, Dec 18, 2009 at 7:40 AM, Robin Myers <email@hidden> wrote:
>>> Every digital camera profiling application I know, with the exception of those designed to work with their own chart (e.g. QP Color 201 chart), work with at least one of the ColorChecker chart family.
>>>
>>> Since X-Rite makes the SG charts very consistently, these other software vendors simply measured their copy of the SG chart to get reference values.
>>>
>>> I think X-Rite should provide reference values, but the workaround is easy enough that it is not a big problem.
>>>
>>> Robin Myers
>>>
>>
>
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