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.
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.
Light emitting diode lamps are flavour of the month, and deliver big energy savings, good colour rendering, dimmability and a long life. The best ones are difficult to distinguish from incandescent lamps. But they come with a hefty price tag – of up to £30 a lamp. And many Chinese versions are, well, rubbish.