lumens to par/pur conversion


New member
Hey everyone, was talking to a fellow reefer about a new mh bulb I was buying and that it listed lumen count (supposedly 3000 for the 14k I bought) and didn't list par. He said he read about a conversion on RC, but I, for the life of me, can't find it. Anyone familiar with it, if it exists? Or can ya tell me if 3000 lumens is a decent rating for a 70w mh?



New member
Found it on Its made by 'marine color'; came from China, couldn't pass up the fact that it was 20bux w/ shipping. If it puts out crappy light or the sps don't take, I'm only out 20 and can swap the old bulb in until I get something else (moving from a 20k unknown make to this 14k).


New member
the best bulb in the 70watt variety is the astralux 14k. btw, par is the portion of the light spectrum thats referred to as photosynthetically active radiation, lumens are a measurement base on what the human eye can see, im not sure if there is some type of conversion for this and if there is it is probably very complicated


In Memoriam
shag is right, there is no way to convert directly... they are measuring two different sets of wavelengths. Its just like saying, 'how much light 10% blue, 40% green, and 50% red equals the light of 33% blue, 33% green, 33% red?' You cant compare the two directly. That being said, if the wavelength of the bulbs do not change, you could come up with a rough conversion for things that dont change... but comparing different color bulbs will lead to errors if comparing PAR and lumens/lux.

As you can see from the following tables, the direct conversion is not possible, as it varies depending on the color of the bulb/source...