Conditions of shooting a white and a black lusterless sheet of paper: a lens is unfocused, ISO 320.

Light sources:

I - daylight, cloudy,

II - incandescent lamp, 150 W,

III - luminescent lamp LÁ6,

IV - halogen lamp, 150 W 220V,

V - candle.

	I	II	III	VI	V
Manual
7500K
6500K
5500K
4500K
4000K
3700K
3000K
Auto

When adjusting a white balance manually one can obtain a normal balance with actually any source. An auto balance mode mustn't actually work normally if daylight is not a main source (you can see it from the table). It is necessary for a fine adjustment of a white balance if a spectrum of the source doesn't differ much from that of daylight.

Measurement of signal level and noise level: levels of a signal and a standard deviation according to "Histogram" option from Photoshop 5.5 for L 185 and 25 brightness, 15*15 pixels area (linear dimensions changed with area remaining the same in order to prevent illumination space discontinuity effect). Noise level is given in dB; the calculation was implemented according to 20Lg formula (deviation/signal).

	signal	standard deviation	noise, dB	R	standard deviation	noise, dB
I	186.4	0.68	-48.8	190	0.87	-46.8
	27.6	1.36	-26.2	30.13	2.42	-21.9
II	187.3	1.16	-44.2	192	1.93	-40
	26.6	1.57	-24.6	26.16	2.18	-21.6
III	185	1.5	-41.8	185.6	1.9	-39.8
	25.6	1.46	-24.9	26.7	2.77	-19.7
IV	182	1.07	-44.6	182	1.6	-41.1
	26.6	1.42	-25.4	27.1	2.37	-21.2
V	185	2.08	-39	207.6	2.22	-39.4
	25.5	1.6	-24	31	2.3	-22.6

	G	standard deviation	noise, dB	B	standard deviation	noise, dB
I	185	0.8	-47.3	182.7	1.25	-43.3
	26.3	1.56	-24.5	28.13	1.6	-24.9
II	187.7	1.6	-41.4	173.7	3.17	-34.8
	24.8	1.99	-21.9	38	4.93	-17.7
III	186	1.79	-40.3	178	2.88	-35.8
	23.5	2.07	-21.1	33.2	4.45	-17.5
IV	182.3	1.5	-41.7	182.2	2.7	-36.6
	25	1.88	-22.5	33.6	5/13	-16.3
V	182	2.3	-37.9	141	4	-30.9
	20.8	2.3	-19.1	351	5/2	-16.6

When adjusting white balance a signal in every R G B channel is different. That is why you should note that an additional light source which will shift the total sensitivity to a "noisy" channel can spoil an image. In case of a candle (its color temperature is 1800 K, what is out of a range of manual balancing of the camera) all channels "make noise". In case of an incandescent lamp it is a blue channel that makes noise most of all. Indoors you'd better use a halogen lamp, a luminescent will lose in a red and a green channel, and an incandescent will lose in a blue channel.

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