hm. using 5000k results in your camera wb as ~13000k, using the first
daylight one results in ~9300k. you get to choose, i don't have to work
with files from that camera..
j.
On Tue, Dec 17, 2013 at 8:29 AM, Chris Siebenmann <[email protected]>wrote:
> Somewhere in the Darktable Redmine system I have a couple of
> contributed white balance coefficients for a range of D7100 white
> balances (both the presets and a range of absolute K values). I think
> that 5000K should be used as the 5000K normalization point.
>
> (If I remember the D7100 manual's discussion of this correctly, also
> reported in the Redmine system, the plain 'daylight' preset is close
> to but not quite on 5000K. So Darktable might as well use the one that
> Nikon claims is exactly 5000K.)
>
> - cks
>
> | the k values are pretty hacky, so don't shudder reading on..
> |
> | these are normalized to daylight wb, which is said to be 5000k. the
> | values live relative to that. so that's somewhat an approximation,
> | and we have to try to get daylight balance from somewhere. judging
> | from a quick look at your raw i don't think we get daylight white
> | balance values from anywhere, i think we first check the raw file,
> | then the wb presets for something with the name `daylight' and then
> | fall back to something totally idiotic (i'm quite sure that's what
> | happens here). the d7100 seems to have daylight wb presets, but with
> | more esoteric names. which one would you prefer to be used as 5000k
> | reference? daylight fluorescent, white, or 5000k?
> |
> | /me tries a few things.
> |
> | j.
> |
> |
> | On Tue, Dec 17, 2013 at 8:12 AM, Chris Siebenmann <[email protected]
> >wrote:
> |
> | > | > It's easiest to explain what I'm seeing with a sample NEF and its
> | > | > embedded preview:
> | > | > http://www.cs.toronto.edu/~cks/tmp/darktable/DSC_4429.NEF
> | > | >
> http://www.cs.toronto.edu/~cks/tmp/darktable/DSC_4429_preview4.jpg
> | > |
> | > | Your second link is broken, looks like it should be:
> | > |
> | > | http://www.cs.toronto.edu/~cks/tmp/darktable/DSC_4429-preview4.jpg
> | >
> | > Oops, yes. My fault and thanks for letting me know. (I've added a
> | > symlink so that it works now, or at least so that it should.)
> | >
> | > | IIRC, it was stated that the temperature control on the white balance
> | > | module is for convenience only, and the value is not related to any
> | > | objective measure... of course, if it's maxing out, that's not very
> | > | convenient. :)
> | >
> | > My view is that getting it into the rigth ballpark is important for
> | > both adjustability (a 100 kelvin change means more at lower K values)
> | > and for understanding what's going on and general usability. For
> | > example, the D7100 '5000K' white balance present currently comes out
> | > with a DT K value of 8364K and the 'shade' preset to 17199K. And if the
> | > values are arbitrary and way off, clamping them to 23000K is (as you
> | > mentioned) not too useful.
> | >
> | > (Part of the usability is for adopting processing suggestions written
> | > for other RAW processors to Darktable. Right now, 'add 200K of white
> | > balance' is not really useful or easily adoptable directions for at
> | > least some cameras.)
> | >
> | > In fact I would go so far as to say that if Darktable's Kelvin scale
> of
> | > colour temperature is so arbitrary and so far off the scale should not
> | > be called '(kelvin) colour temperature'. Call it 'white balance index'
> | > and scale it differently using whatever units are convenient.
> | >
> | > (Of course I would prefer if DT really had a Kelvin colour temperature
> | > scale and it worked right. But clearly it doesn't right now, so the
> | > easiest fix may be some redefinitions. This might also allow for it to
> | > be in more convenient units for changes.)
> | >
> | > - cks
>
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