On Tue, Jul 2, 2013 at 10:04 PM, johannes hanika <[email protected]> wrote:
>
> On Wed, Jul 3, 2013 at 7:41 AM, Emmanuel Lacour <[email protected]> wrote:
>>
>> On 02/07/2013 20:10, Pascal de Bruijn wrote:
>>>
>>>
>>> I just downloaded three random 5DmkII samples from photographyblog,
>>> and imported them into darktable-1.1.x which has the same temperature
>>> code as git master.
>>>
>>> I got the following three Kelvin values for shots that seem to have
>>> been shot in plain daylight:
>>>
>>> 6173K
>>> 5768K
>>> 4638K
>>>
>>
>>
>> on this one:
>> http://img.photographyblog.com/reviews/canon_eos_5d_mark_ii/sample_images/canon_eos_5d_mark_ii_08.cr2
>>
>> I have 3223°K and a visual near the jpg one (a little bit warmer)
>>
> comparisons to the jpg are really very useless, there is such a lot of
> differences between the two processing pipeline that it's not enough at all
> to look at white balance. actually the wb coeffs might be the only thing
> that we read out of the raw in a meaningful way and apply similarly to the
> jpg processing in your camera.
>
> about the kelvin numbers: these are dreamed up by taking what the camera or
> our presets claim to be daylight balance, identifying it as about 5000 or
> 5500K and inferring a value for your current rgb coefficients from that (as
> pascal said, very unscientific that part). it does seem a little odd that
> the daylight preset ends up at 3400K, that's true. as mentioned somewhere in
> this thread, this is a mere UI thing though, the number doesn't matter at
> all for image processing, that's done using the rgb coefficients.
>
> reverting pascal's commit will result in 5507K for daylight balance instead,
> so i guess you have a valid point there.

Not at all...

The "Daylight" wb-preset lists 4923K over here (darktable-1.1.x tree,
but it should have the same code as master for temperature). around
5000K is fine.

Regards,
Pascal de Bruijn

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