Part 2: Lighting Standards

There are two commonly used lighting standards, the D50 and D65 standards defined by the International Commission on Illumination, CIE (Commission internationale de l'├ęclairage). The D series of illuminants are constructed to represent natural daylight.

D65_Spectrum

D65 corresponds roughly to the average midday light in Western Europe / Northern Europe (comprising both direct sunlight and the light diffused by a clear sky), hence it is also called a daylight illuminant. "[D65] is intended to represent average daylight and has a correlated colour temperature of approximately 6500 K. CIE standard illuminant D65 should be used in all colorimetric calculations requiring representative daylight, unless there are specific reasons for using a different illuminant."ISO 10526:1999/CIE S005/E-1998, CIE Standard Illuminants for Colorimetry. Because D65 is a combination of direct midday light and light from the northern sky it is slightly blue in colour. It is used in the television industry and is the standard lighting for the sRGB colour space and from this the World Wide Web.

D50_Illumination

D50 Illuminant

ISO 3664:2009 specifies the CIE illuminant D50 with a correlated color temperature of approximately 5000┬░ Kelvin as the standard illuminant to be used as a light source for viewing and assessing color for the graphic technologies and photography. Being slightly warmer than D65 makes the D50 standard better for print matching as photographic papers tend to be slightly warm.

 

In summary so far, if you want to display photos on a computer monitor for example web display you should use the following parameters in your calibration setup:

White Point -  6500 degrees kelvin

Gamma - 2.2

Brightness - 80 cd/m^2

 

 

Contrast Ratio - 200:1 (Black Point of 0.4 cd/m^2)

Most monitors and projection systems are set very bright so depending on where you are displaying your images it may be better to set your calibration brightness to 100 - 120 cd/m^2. Most projection systems seem to be much brighter than our computer monitor screens.

 

If you wish to match to a print then the following settings should be used as a starting point:

White Point -  5000 degrees kelvin

Gamma - 2.2

Brightness - 80 cd/m^2

Contrast Ratio - 200:1 (Black Point of 0.4 cd/m^2)

Depending on how sophisticated your calibration system is you may not have control over all the above parameters. For example I have been trailing the Spyder3Pro software and it does not have control of the black point and therefore does not dave control over the contrast ratio. It also suggested a brightness that was not in line with what I wanted. The system could be fooled to use the desired value because the setting of the brightness is done manually utilizing the monitor brightness control.

 

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