In previous article, we mentioned about the concept that under different circumstances people feel different light brightness. Even these lights come from the same lamp. The most important reason is that radiations energy will change the brightness of this light in our eyes. For example, if the ground and walls are blue. In same luminous flux, high efficiency white LED looks much brighter than filament lamp. In the optical spectrum of white LED lights, the peak value of the light intensity distribution is between 466nm and 485nm (blue-ray). Thus most of the light coming from white LED lights will be reflected by the ground and walls. On the contrary, if the ground and walls are red colored, more light from filament lamps will be reflected. In such condition, we cannot simply conclude that high efficiency white LED looks brighter than filament lamp in same luminous flux. That is all depends on surroundings.
So far, we have concluded two different results. One is from the measurement result of illuminometer and the other one is from our eyes’ feeling. Differences between them are caused by the unscientific measuring method. In the matter of fact, using illuminometers to measure luminous flux is not as accurate as we all considered. The light measured by illuminometers is light directly coming from light sources, and the light caught by our eyes is mostly from the ground. They are totally different objects. But why designers and engineers still use this method to measure the luminous flux? Firstly, this method is relatively easy compare to other methods. Secondly, it can provide a rough measuring result in most conditions. Finally, illuminometers are much cheaper. These three advantages make illuminometers frequently used in situations that accurate brightness data is not necessary. Many design houses for residential decorations use this method to reduce their cost.
In conditions that LED high bay light intensity results are required, methods measuring light intensity are more accurate. Engineers can measure the light intensity on the surface of the ground and walls directly. Values measured by this method will be much more closed to results perceived by human eyes. Brightness meter is an optical instrument typically used to measure light intensity. But this instrument is more expensive than illuminometer and Eneltec LED Flood Lights. In commercial field, brightness meter is not so popular as illuminometer.