I'd say go with the 5000k value(s) in the abscence of better information.
Unfortunately I don't have Nikon's official software (or any commercial
software) that could be used to double-check the nominal official WB to
try to match their results. If someone does have Capture NX or Lightroom
or etc to check I'd be interested in what the results are.
(I tried Nikon's free View NX2 software in a Windows VM but I couldn't
get it to report the actual white balance colour temperature. It did
seem to avoid the initial magenta colour bias, though.)
- cks
| 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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