Re: [darktable-user] White balance on a TrueColor scuadra, using provided Lab values

[KOVÁCS István]

One more thing regarding the colour picker: it works in your display's
colour space, which may affect its Lab readings - the devs would know.
https://www.darktable.org/usermanual/ch03s03s04.html.php


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Re: [darktable-user] White balance on a TrueColor scuadra, using provided Lab values

[KOVÁCS István]

My bad, sorry, I thought the card had colour patches, too - I've only ever
used a simple Whibal card, and does not provide Lab values. Also, I don't
understand why you mentioned exposure in your post, I thought you expected
darktable to adjust it automatically when you picked white balance from the
card. Sorry about that.

Kofa


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Re: [darktable-user] White balance on a TrueColor scuadra, using provided Lab values

[Emmanuel Lacour]

Le 05/09/2016 à 13:47, KOVÁCS István a écrit :
> Hi,
> 
> If I get this correctly, the card has grey patches as well as colour ones.

no, only grey (and blck/white, but I don't really use them):

http://www.scuadra.fr/en/charte.php?Language=en


it's mostly for WB

> The spot white balance tool adjusts white balance only, meaning that:
> - after adjustments, grey should be grey (neutral)


but it's practically impossible to produce materials with exact neutral
grey as standardized in photo. Hence, each grey card gives accurate Lab
values measured by spectrophotometer, so I tried to find a quick way to
adjust the WB based on those values.

> - exposure is to be done independently

of course.

> - colour in non-grey patches, as well as the lightness of all patches
> are influenced by the camera profile. See darktable's documentation on
> that topic.
> 

right, but it seems would be welcome to adjust the spot WB measure using
Lab values if we know them maybe?

> Of course I may have misunderstood something.
> 

me too ;)

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Re: [darktable-user] White balance on a TrueColor scuadra, using provided Lab values

[KOVÁCS István]

Hi,

If I get this correctly, the card has grey patches as well as colour ones.
The spot white balance tool adjusts white balance only, meaning that:
- after adjustments, grey should be grey (neutral)
- exposure is to be done independently
- colour in non-grey patches, as well as the lightness of all patches are
influenced by the camera profile. See darktable's documentation on that
topic.

Of course I may have misunderstood something.

Kofa

On 5 Sep 2016 11:50, "Emmanuel Lacour"  wrote:

> Le 05/09/2016 à 11:13, Sebastian a écrit :
> > Have you tried the spot white balance preset?
> >
> > See also https://www.darktable.org/usermanual/ch03s04.html.php#
> whitebalance
> >
> >
>
> that's what I use, but after using the spot WB, I check the Lab values
> using the color picker on the same area and values are not the one given
> on the grey card. So I have to manually adjust the white balance, which
> is fastidious with many try/check to be done. I also need to use the
> exposure module to get the right L value.
> 
> 
> darktable user mailing list
> to unsubscribe send a mail to darktable-user+unsubscribe@
> lists.darktable.org
>
>


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Re: [darktable-user] White balance on a TrueColor scuadra, using provided Lab values

[Emmanuel Lacour]

Le 05/09/2016 à 11:13, Sebastian a écrit :
> Have you tried the spot white balance preset?
> 
> See also https://www.darktable.org/usermanual/ch03s04.html.php#whitebalance
> 
>

that's what I use, but after using the spot WB, I check the Lab values
using the color picker on the same area and values are not the one given
on the grey card. So I have to manually adjust the white balance, which
is fastidious with many try/check to be done. I also need to use the
exposure module to get the right L value.

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Re: [darktable-user] White balance on a TrueColor scuadra, using provided Lab values

[Sebastian]

Have you tried the spot white balance preset?

See also https://www.darktable.org/usermanual/ch03s04.html.php#whitebalance


On 09/04/2016 07:51 PM, Emmanuel Lacour wrote:
> Dear DT users,
>
>
> I have a TruColor grey card, and I just saw that when I use the WB
> module to spot on it, the measured Lab values are not the one written on
> the card. Trying to adjust using the sliders of the WB module is a night
> mare :(
>
> Isn't there another way to accuratly adjust WB using this card and the
> Lab values provided by the manufacturer?
> 
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> to unsubscribe send a mail to darktable-user+unsubscr...@lists.darktable.org
>

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