Converting milliwatts/cm2 to lumens/cm2

OK, I noticed on the tech sheet for the gray resin that Formlabs determined the optimal UV light output is 1.25 milliwatts per square centimeter. Does anyone know how to convert that to lumens per square centimeter?

The reason I’m asking is lumens is how my UV LED’s are measured in.

Should I assume the value Formlabs published is the area of their test chamber?

Thanks, Matt

Try this:

But… Lumens is a measure of how light is perceived by the human eye. You can’t really convert it to Watts which is a measure of power.

1 Like

Thanks Randy! That’s what I’m looking for. Thanks for the conversion website; I’ll be adding it to my collection of units converters.

Even if it’s not an exact conversion and I’m trying to compare apples to oranges; ballpark is good enough for my needs.


Just remember, Lumens is what the eye sees (which is why lightbulbs are rated in Lumens). A Lumen is how much energy is present at 555nm, which is the sensitivity peak in human visual perception. But the frequency we care about is 405nm (or so). The LEDs ought to be “brighter” at the lower frequency. So while you won’t know how many watts you’re getting at 405nm you’ll know the wattage at 555nm and that the LEDs are brighter than that at 405nm.

I think.

I’m not an expert in physics or optics…

1 Like

It sounds like you know more about optics than I do. I appreciate your help.