Candle & Lumen

[andromeda.73]

I can not make comparisons between candle and Lum. For example, the Polarion PF40 has 4200 lum, many candle match?

 

[Search]

If I understand you right, you are asking what 4200 lumens converts to candlepower. In that case, there is no way of knowing.

Lumens measures total light output.

Candlepower (aka lux) is how much light is at a certain spot.


If all beams were the same, then there would be a formula to convert them.

 

[AlexLED]

As Search stated, for the conversion you need to know the beam angle.

A rough estimate can be found here:
http://led.linear1.org/how-do-i-convert-between-candelas-and-lumens/

beam angle -> cd/lm
5 -> 167.22
10 -> 41.82
15 -> 18.60
20 -> 10.48
25 -> 6.71
30 -> 4.67
35 -> 3.44
40 -> 2.64
45 -> 2.09

 

[andromeda.73]

thanks for explanation.

 

[slappomatt]

As Search stated, for the conversion you need to know the beam angle.

A rough estimate can be found here:
http://led.linear1.org/how-do-i-convert-between-candelas-and-lumens/

I'm sure this would get you pretty close but because of differences in hot spot VRS spill there really is no way to tell exactly with out meters. The ceiling bounce test is pretty effective for comparing different lights total output.

 

[andromeda.73]

Tank's! :wave:

 

[KeyGrip]

In the case of a Polarion light, I think the general rule of thumb for candlepower (intensity at a given distance) is usually "a whole lot"

 

[baher_fawzy]

help the value is half

please i have some problems in calculating the lumen output
of the halogen lamp (dichoric)
when i convert the CD to Lm by using
i use this formula " Lm = Cd 2pi[1 - cos(phi / 2)]
or the table using 36 degree or calculator (http://led.linear1.org/lumen.wiz)
at CD = 1450
1- Lm = 445 lm
2- by calculator 445 Lm

..... BUT
the result is half the value i measured actually by using Goniophotometer
if this formula is valid for Led lamps only ?
if so please i want the formula which i measure the luminous flux of the halogen lamp

thanks too much

 

[Jay R]

I always explain it this way to non-technical people.
What gives off more light, a pinhead at brightness'50' or a wall at '1'.

Or I say, what contains more heat, a teaspoon of boiling water or a swimming pool at 20 degrees.

One may be brighter / hotter but the other has more light / heat