[argyllcms] Re: Capture One Profiles
- From: Maciej Bryński <maciek@xxxxxxxxxx>
- To: argyllcms <argyllcms@xxxxxxxxxxxxx>
- Date: Sun, 7 Jul 2013 18:29:52 +0200
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
Other related posts:
