Candela vs lumen

**chuckman** · 01-19-22, 07:32

To me they appear (key word) to have the same definition, just worded differently. What's the difference, and how does it impact real-world use? Explain it like I am 6 years old.

**dmd08** · 01-19-22, 08:07

Lumens is the overall light output measured in an integrating sphere with no regard for which direction the light is going.

Candela is a measure of how powerful a beam of light is, or how well the lumens are concentrated into a beam.

Two different units of measurement but can be correlated depending on reflector or optic design. As lumens go up, candela will go up given the same reflector or optic. But a very efficient reflector or optic could have higher candela but lower lumens than another light with a very diffuse beam pattern even though technically it puts out more light.

That's my basic, layman's understanding at least. I'm open to correction from the professionals.

**Defaultmp3** · 01-19-22, 09:21

Originally Posted by dmd08

Lumens is the overall light output measured in an integrating sphere with no regard for which direction the light is going.

Candela is a measure of how powerful a beam of light is, or how well the lumens are concentrated into a beam.

I think the most obvious thing to note that lumens = candela * steradian (and so candela = lumens / steradian), steradian being a unit of solid angle.

From Wiki:

A good rule of thumb for current WML technology is that high candela is oriented at high throw, minimal spill, while high lumens is oriented at minimal throw, but great spill.

**Five_Point_Five_Six** · 01-19-22, 09:23

Lumens can be deceptive, candela isn't.

The SF M600DF is a 1500 lumen light with 16,000 candela, and is less desirable to me than my Arisaka/Malkoff 500 lumen light with 55,000 candela.

Lumens is overall output, candela is how far that light can punch out there.

**chuckman** · 01-19-22, 09:34

Originally Posted by Five_Point_Five_Six

Lumens can be deceptive, candela isn't.

The SF M600DF is a 1500 lumen light with 16,000 candela, and is less desirable to me than my Arisaka/Malkoff 500 lumen light with 55,000 candela.

Lumens is overall output, candela is how far that light can punch out there.

Thank you, THIS I understand.

**markm** · 01-19-22, 11:32

I'm flashing back to the candlepower forums.

**Adrenaline_6** · 01-19-22, 12:06

Think of it like a garden hose. Lumen is total gallons of water being dispensed per minute. With a certain lens, you can have it spray wide where it covers a lot of area but doesn't go very far or you can have a tighter stream where it doesn't cover a lot of width, but goes a lot farther.

Candela is the definition of how far it goes.