From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mailout4.w1.samsung.com ([210.118.77.14]:20240 "EHLO mailout4.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966066Ab2EPJeg (ORCPT ); Wed, 16 May 2012 05:34:36 -0400 MIME-version: 1.0 Content-transfer-encoding: 8BIT Content-type: text/plain; charset=UTF-8 Received: from euspt2 ([210.118.77.14]) by mailout4.w1.samsung.com (Sun Java(tm) System Messaging Server 6.3-8.04 (built Jul 29 2009; 32bit)) with ESMTP id <0M43007XTZY09030@mailout4.w1.samsung.com> for linux-media@vger.kernel.org; Wed, 16 May 2012 10:34:48 +0100 (BST) Received: from linux.samsung.com ([106.116.38.10]) by spt2.w1.samsung.com (iPlanet Messaging Server 5.2 Patch 2 (built Jul 14 2004)) with ESMTPA id <0M4300ESKZXJ7Z@spt2.w1.samsung.com> for linux-media@vger.kernel.org; Wed, 16 May 2012 10:34:32 +0100 (BST) Date: Wed, 16 May 2012 11:34:33 +0200 From: Sylwester Nawrocki Subject: Re: [PATCH 03/23] V4L: Add an extended camera white balance control In-reply-to: <20120516065715.GK3373@valkosipuli.retiisi.org.uk> To: Sakari Ailus Cc: Sylwester Nawrocki , linux-media@vger.kernel.org, m.szyprowski@samsung.com, riverful.kim@samsung.com, sw0312.kim@samsung.com, Kyungmin Park Message-id: <4FB374A9.60901@samsung.com> References: <1336645858-30366-1-git-send-email-s.nawrocki@samsung.com> <1336645858-30366-4-git-send-email-s.nawrocki@samsung.com> <20120514000234.GG3373@valkosipuli.retiisi.org.uk> <4FB2CA63.2000605@gmail.com> <20120516065715.GK3373@valkosipuli.retiisi.org.uk> Sender: linux-media-owner@vger.kernel.org List-ID: Hi Sakari, On 05/16/2012 08:57 AM, Sakari Ailus wrote: ... >>>> + >>>> + >>>> + V4L2_CID_AUTO_N_PRESET_WHITE_BALANCE >>>> + enum v4l2_auto_n_preset_white_balance >>>> + 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. >>>> + >>>> + >>>> + >>>> + >>>> + >>>> + V4L2_WHITE_BALANCE_MANUAL >>>> + Manual white balance. >>>> + >>>> + >>>> + V4L2_WHITE_BALANCE_AUTO >>>> + Automatic white balance adjustments. >>>> + >>>> + >>>> + V4L2_WHITE_BALANCE_INCANDESCENT >>>> + White balance setting for incandescent (tungsten) lighting. >>>> +It generally cools down the colors and corresponds approximately to 2500...3500 K >>>> +color temperature range. >>>> + >>>> + >>>> + V4L2_WHITE_BALANCE_FLUORESCENT >>>> + White balance preset for fluorescent lighting. >>>> +It corresponds approximately to 4000...5000 K color temperature. >>>> + >>>> + >>>> + V4L2_WHITE_BALANCE_FLUORESCENT_H >>>> + With this setting the camera will compensate for >>>> +fluorescent H lighting. >>>> + >>> >>> 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: + V4L2_WHITE_BALANCE_FLUORESCENT_H + Variant of V4L2_WHITE_BALANCE_FLUORESCENT + for fluorescent lamp lighting with spectral power distribution more similar + to daylight. + ? >>> 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