light output depreciation will result from optics over the led light

As LED light travels through an object such as a pc len, it loses intensity depending on the clarity of the optics. This is due to inherent losses through  the pc optics as LED light travels from air through the lens back to air.

These losses are present no matter the type of LED light. The losses related with the lens material and optics can vary from 5% to 20%. An open optic lamp will produce higher effective lumens as the light doesn’t have to shine through anything, but the reflector of the open optic has to be precisely focused to get the maximum result from the LED light. A dirty, scratched or dull lens or reflector will greatly influence the beam pattern of light.