[argyllcms] Re: Capture One Profiles
- From: "Matthew H. Owens" <matt@xxxxxxxxxxxxxxxxxxxx>
- To: "argyllcms@xxxxxxxxxxxxx" <argyllcms@xxxxxxxxxxxxx>
- Date: Sun, 7 Jul 2013 09:55:10 -0700
And all of that, my friends is why I bought one of those crazy expensive Cruse
Museum Scanners. Lighting is so much more controllable. Yes it has its
limitations, as do cameras, variable lighting arrays, and the various cameras
that do the capture, and the post processing methodologies used to create a
usable image. Blech!!! Fun, Fun, Fun!!
Matthew H. Owens
Founder
Druidian Archival Service
www.druidian.org
Archival Studio +1(602)492-3770
On Jul 7, 2013, at 9:29 AM, Maciej Bryński <maciek@xxxxxxxxxx> wrote:
> 2013/7/7 Ben Goren <ben@xxxxxxxxxxxxxxxx>:
>> On Jul 7, 2013, at 6:50 AM, Iliah Borg <iliah.i.borg@xxxxxxxxx> wrote:
>>
>>> On Jul 7, 2013, at 2:21 AM, Maciej Bryński wrote:
>>>
>>>>
>>>> I tried on this (it has the smallest a* and b* values)
>>>> GS11 14.77 15.32 12.62 46.07 -0.00 0.06
>>>> 0.16 176.17 0.81 0.81 0.81 0.81
>>>
>>> I see. However Lab values are not enough to judge the spectral response
>>> flatness, one needs spectral measurements to be sure. On my cards GS11 is
>>> far from spectrally flat.
>>
>> As an example, one would hope that your display that you're reading these
>> words on would have a white that lies on the neutral axis (for D50 or D65 or
>> whatever your chosen white point is), but it's as not-spectrally-flat as it
>> gets: three narrow spikes of red, green, and blue. (PTFE (Teflon) thread
>> tape and Tyvek, on the other hand, both have very flat (visible) spectra and
>> are 98%+ reflective.)
>
>> This is why I'm a fan of using the profiling mechanism to determine the
>> white point. You could have a chart with nothing even remotely close to
>> spectrally flat or even with neutral tristimulus values, and you'll still
>> get perfect white balance and exposure.
>
>
>
>>> QPcard
>>> http://www.qpcard.com/en_b2c/color-reference-cards/qpcard-203-card.html is
>>> not very expensive, and it allows better camera profiles compared to IT8.
>>
>> I think Maciej might have mentioned that he's got a ColorChecker Passport,
>> which is better than the QPCard (which is, in turn, better than an IT8) for
>> camera profiling. And the latest version of Argyll has reference files for
>> the Passport.
>
> I have ColorChecker Passport.
> WB on grey card varies from 5150 to 5250 K with tint from -1 to 0.
> So it's not impressive.
>
> Graeme,
> Have you thought about adding option to calculate profile without WB shift ?
>
>> Maciej, it's also worth considering making your own chart. Assuming you've
>> got a spectrophotometer, all you need is a bunch of artist's paints and a
>> printer. Get as many different paints as you can. Golden Fluid Acrylics is a
>> good choice if you're buying, or just spend some time in a painter's studio.
>> Plan it all out ahead of time. You'll want at least the base paint by itself
>> and another patch (or more) mixed with white. Other mixtures aren't a bad
>> idea. Figure out how many patches total you'll have, how many painted
>> patches, and generate the difference with Argyll. Lay it all out in
>> Photoshop (or whatever), print it on whatever paper you've got that has no
>> optical brighteners and the largest possible gamut (and glossy is fine,
>> since you need to light it in a way that doesn't throw specular reflections
>> even if it's a matte target), and paint squares by numbers. Measure with the
>> spectrophotometer and you're done.
>
> Unfortunately I have only colorimeter (I1Display Pro). And device like
> I1 Pro 2 is out of my price range.
>
>> You could spend as much on paint as you would on a ColorChecker Passport and
>> have a chart that far surpasses any you can buy commercially -- and have
>> enough paint left over to make many dozens more.
>
> Maybe I can show what I'm talking about.
> One photo, two profiles. (ProfileMaker and Argyll). Both have average
> dE less than 1. And I DO see a difference. (photos are in AdobeRGB)
> http://public.brynski.pl/profile/argyll.jpg
> http://public.brynski.pl/profile/profilemaker.jpg
>
>> Cheers,
>>
>> b&
>
> Regards,
> --
> Maciek Bryński
>
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