On Mon, Dec 31, 2012 at 5:58 PM, Eckhart Pedersen
<[email protected]> wrote:
> On 2012-12-31 14:37, Pascal de Bruijn wrote:
>>>> Does this mean that if I were to create my own input profile based on a
>>>> test chart and with the correct settings, I would be able to get (more
>>>> or less) natural looking images without a base curve?
>> Yes, because a proper (ICC) camera input profile has an XYZ matrix and
>> curves internally. So it's basically the same thing, just applied in a
>> single step. So you need to disable the basecurve because otherwise
>> you'd have two sets of curves being applied on top of each other.
> Yes, this is exactly what I suspected. So if I were to create my own
> input profile and shoot with a gray card, I should be able to get the
> most faithful rendering that is possible (whether this faithful
> rendering looks good is another matter).

Still, if you have wildly varying lighting conditions, you might need
to do per situation profiles as well. It just depends on how nitpicky
you want to be :)

>> As written earlier, Darktable uses the Adobe DNG D65 XYZ matrices (via
>> dcraw). These do not come with curves. Other raw converters supplement
>> this (visible or not) with an arbitrarily deformed 2.2 gamma curve. We
>> just took it a step further to provide vendor tuned curves out of the
>> box which are user visible and controllable. We are very transparent
>> in that way.
> Yes, I can see how this approach gives the user more flexibility, which
> is great! I just needed to understand why my images did not look as
> expected, and now that I know, I am very happy with the way darktable works.

:)

>> So to get a so-called neutral color rendition, anything but a custom
>> color profile is mostly just an arbitrary choice.
>>
>> Now here are some notes on how to do a custom profile for darktable:
> Thank you very much, this is much appreciated. I am a bit sorry for the
> effort you put into writing this, as I already watched your excellent
> screencast about creating custom input profiles. I don't think a
> separate blog post is needed, the screencast is really great!

The screencast details how to do a matrix-only profile (which DOES
need the basecurve).

So the new instructions might deviate a little, so when doing a (more
normal) matrix+gamma/shaper profile please do follow these latest
instructions.

That said, I haven't worked in this way for some time, so you might
need to experiment a bit for optimal results. But I gave the
instructions in the earlier post a try this afternoon and the result
seemed quite ok.

> Again, thank you for your work and your help, it is greatly appreciated.
> And have a great new year :)

Happy new year. :)

Regards,
Pascal de Bruijn

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