Hi Sakari,
On 05/16/2012 08:57 AM, Sakari Ailus wrote:
...
>>>> +
>>>> + <row id="v4l2-auto-n-preset-white-balance">
>>>> + <entry spanname="id"><constant>V4L2_CID_AUTO_N_PRESET_WHITE_BALANCE</constant> </entry>
>>>> + <entry>enum v4l2_auto_n_preset_white_balance</entry>
>>>> + </row><row><entry spanname="descr">Sets white balance to automatic,
>>>> +manual or a preset. The presets determine color temperature of the light as
>>>> +a hint to the camera for white balance adjustments resulting in most accurate
>>>> +color representation. The following white balance presets are listed in order
>>>> +of increasing color temperature.</entry>
>>>> + </row>
>>>> + <row>
>>>> + <entrytbl spanname="descr" cols="2">
>>>> + <tbody valign="top">
>>>> + <row>
>>>> + <entry><constant>V4L2_WHITE_BALANCE_MANUAL</constant> </entry>
>>>> + <entry>Manual white balance.</entry>
>>>> + </row>
>>>> + <row>
>>>> + <entry><constant>V4L2_WHITE_BALANCE_AUTO</constant> </entry>
>>>> + <entry>Automatic white balance adjustments.</entry>
>>>> + </row>
>>>> + <row>
>>>> + <entry><constant>V4L2_WHITE_BALANCE_INCANDESCENT</constant> </entry>
>>>> + <entry>White balance setting for incandescent (tungsten) lighting.
>>>> +It generally cools down the colors and corresponds approximately to 2500...3500 K
>>>> +color temperature range.</entry>
>>>> + </row>
>>>> + <row>
>>>> + <entry><constant>V4L2_WHITE_BALANCE_FLUORESCENT</constant> </entry>
>>>> + <entry>White balance preset for fluorescent lighting.
>>>> +It corresponds approximately to 4000...5000 K color temperature.</entry>
>>>> + </row>
>>>> + <row>
>>>> + <entry><constant>V4L2_WHITE_BALANCE_FLUORESCENT_H</constant> </entry>
>>>> + <entry>With this setting the camera will compensate for
>>>> +fluorescent H lighting.</entry>
>>>> + </row>
>>>
>>> I don't remember for quite sure if I replied to this already... what's the
>>> diff between the above two?
>>
>> No, you didn't, otherwise I would certainly remember that ;)
>>
>> V4L2_WHITE_BALANCE_FLUORESCENT_H is for newer, daylight calibrated fluorescent
>> lamps. So this preset will generally cool down the colours less than
^^^^^^^^^
Sorry, I put it wrong. It should have been "warm up", since "cooling down"
the colours happens only for V4L2_WHITE_BALANCE_INCANDESCENT, other presets
just generally warm up colours, with various degree.
>> V4L2_WHITE_BALANCE_FLUORESCENT. I was even thinking about a separate control
>> for V4L2_WHITE_BALANCE_FLUORESCENT, since some ISPs have several presets for
>> fluorescent lighting. I dropped that idea finally though.
>
> I don't know about the daylight calibrated ones, but the older ones often
> tend to give colder light. Nevertheless, I think it'd be good to mention
> this in the documentation. I couldn't have guessed it. :)
Do you think something like this would be OK:
+ <entry><constant>V4L2_WHITE_BALANCE_FLUORESCENT_H</constant> </entry>
+ <entry>Variant of <constant>V4L2_WHITE_BALANCE_FLUORESCENT</constant>
+ for fluorescent lamp lighting with spectral power distribution more similar
+ to daylight.</entry>
+ </row>
?
>>> The colour temperature of the fluorescent light depends on the lamp; 2500 K
>>> is not uncommon here in Finland. It's the spectrum that's different from
>>> incandescents, not necessarily the colour temperature.
--
Regards,
Sylwester
--
Sylwester Nawrocki
실베스터 나브로츠키
Samsung Poland R&D Center
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