Spectrum of a fluorescent lamp, light color 880, acv = 1; Φ = 4000 lm at 25° (54 W).

Change in the spectrum with reduced spectral transmission at the blue end of the spectrum through filters such as plastic materials.

The example of a change in light due to the filter characteristics of dispersion plates is generally valid – irrespective of the type of light source. In actual practice it has an effect principally if the light has a high blue component. The lack of short-wave blue components tends to be inconspicuous and can often only be detected through precise measurements across the entire spectrum. Particular attention must be paid to the aging of plastics under the influence of high temperatures or UV radiation because even slight yellowing can lead to a significant filter effect and therefore to reduced biological effectiveness. A comparable effect with indirect lighting can weaken the biological impact if the wall material or color does not reflect blue light well.