Popularly referred to as energy-saving lamps, compact fluorescent lamps have a poor image because of perceived deficiencies in colour, power and speed to full output. But massive improvements have been made in all these areas thanks to substantial investment by the big lamp manufacturers.
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.
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.