The colour rendering index is determined by a comparison with the standardised black body radiator which is defined as having the "ideal" colour rendering Ra of 100 at every temperature.

The greater the differences in colour between the comparison lamp and the black body radiator at the same colour temperature, the smaller the colour rendering index Ra.

Colour temperature and colour rendering are therefore needed to define the light colour of a lamp.

Note: Every colour temperature can have the ideal value of Ra 100. This means that the colours are rendered in the typical manner for this temperature. This is not always satisfactory, however. For example an incandescent lamp may render blue tones only in a subdued manner despite an Ra value of 99. If fine distinctions are required for blue tones a light colour with a higher colour temperature needs to be selected.

The Ra groups however provide a simple means of classifying light sources in different colour rendering quality levels:

Standard compact fluorescent lamps meet the requirements of colour rendering group 1B or colour rendering group 1A. Rules of thumb for selecting fluorescent lamps.

Basic Information
- Principal of Compact Fluorescent Bulbs
- Compact Fluorescent Lamp Structure
- Luminous efficacy and economy
- Light colour
- Colour temperature
- Colour rendering
- Guaranteed to save electricity. Whatever the shape
- Good for the environment
- The right light colour for each lighting task
- Cultural influences

Replace & Install Compact Fluorescent Bulbs

Incandescent VS Compact Fluorescent Light Bulb
- It's Your Money -- Incandescent VS Compact Fluorescent Light Bulb
- Incandescents - the usual light bulbs

FAQs for Compact Fluorescent Light Bulb

Base for Compact Fluorescent Bulbs
- Normal Base for Compact Fluorescent Bulbs
- Pin-based Compact Fluorescent Bulbs