The term "colour rendering" is sometimes used to refer to the way different types of illumination can cause colours to look different. The characteristics of the light source are therefore referred to as its "colour rendering properties." You can think of a light source's colour rendering properties as a measure of how faithfully it allows you to see colour. When viewed under lighting with poor colour rendering properties, colours will appear differently from what you would expect. For example, candlelight has poor colour rendering properties, making it difficult or impossible to distinguish between subtle differences in colour. It is therefore important to use lighting with good colour rendering properties when you wish to compare or select colours. The colour rendering properties of a light source can be expressed as a number called the "colour-rendering index". This number indicates the degree to which the appearance of colours is distorted under the light source, with a standard, ideal light source having the numerical value, 100. The maximum colour rendering index value is 100. When working with colours, make sure to do so in an environment that is properly illuminated.