Thank you! I just pulled the latest git tip and rebuilt, and now my
sample NEF comes up with a much lower white balance and so on.
- cks
| sorry i was confused, we normalise to D65 daylight, not D50. so i'm
| now using the first preset with `daylight' or similar in the name, not
| 5000k. which unfortunately means that 5000k shows up as 5300odd in the
| gui. not sure i want to special case my way around that, definitely
| not before 1.4 though. fix pushed.
|
| cheers,
| jo
|
| On Tue, Dec 17, 2013 at 9:02 AM, Chris Siebenmann <[email protected]>wrote:
|
| > 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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