The UGR method (Unified Glare Rating) is an international index presented by CIE, the international lighting research body, in its publication 117 and is used to evaluate and limit the psychological direct glare from luminaires. Contrary to previous methods where the glare was rated using the luminance values of a single luminaire, this method calculates the glare of the entire lighting installation at a defined observer position.
Colour rendering is also important. This is the ability of a light source to show surface colours as they should be, usually in comparison to a tungsten or daylight source. Lamps with poor colour rendering will distort some colours.
One aspect of lamp colour is its colour appearance; whether the light from the lamps looks ‘warm’ or ‘cool’, measured by the correlated colour temperature (CCT). Lamps with a warm appearance having a CCT of 2700 – 3000K are generally considered appropriate in a domestic setting. Lamps of 4000K and above are considered ‘cool’ and are more appropriate for office and some retail applications.