Do you want to replace your High Pressure Sodium (HPS) Lights with LED (Light-emitting Diode) but do not know which watts will be ok? You will get the answers by reading the below article which based on some scientific facts and practical experience.
First of all, we need to know what the scotopic Lumens is. It is a concept developed by scientists to estimate the amount of light, more accurate than traditional lumens.
The scientists use S/P ratio to convert the traditional Lumens into pupil Lumens which perceived by our eyes under mesopic light conditions.
We can calculate the approximate pupil lumens by the formula below.
Pupil Lumens = Photopic Lumens * [S/P] 0.78
Here are some types of lights with their traditional and pupil lumens
* A good general idea of what wattage of LED will replace an equivalent HPS wattage , is to divide the HPS wattage by 3.
Except the Lumens output, the color temperature is another important parameter that should be taken into account when replacing HPS fixtures with LED fixtures in some cases. We can see some differences from the below pictures.