cd/m2 <<>> lux

[Currylaw]

Dear experts :

I've got only a lux meter, is it possible to convert lux into cd/m2??
Thanks a lot for your help. :oops:

[Knight]

Dear experts :

I've got only a lux meter, is it possible to convert lux into cd/m2??
Thanks a lot for your help. :oops:

Lux is a measurement of illuminence, where cd/m² is a measurement of luminance.

Lux = 1 lumen/m²
Lumen = The amount of light given out through a solid angle by a source of one candela intensity radiating equally in all directions.

[Currylaw]

Thanks a lot for your soon reply.

But after actual experiment by using two measuring instruments, there would be different readings (such as lux : cd/m2 = 3.6:1).
That's make me confused.

Could you explain further?
Thanks

[Knight]

Thanks a lot for your soon reply.

But after actual experiment by using two measuring instruments, there would be different readings (such as lux : cd/m2 = 3.6:1).
That's make me confused.

Could you explain further?
Thanks

The Lux is defined from the Lumen, which is in turn defined by the Candela.

The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 × 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.

The candela, then simply tells us the intensity of light of being irradiated in all directions. The Candela is independent of distance.

The official definition of the lumen, the unit of luminous flux, is "The luminous flux dF of a source of luminous intensity I (cd) in an element of solid angle dR is given by dF = IdR" This tells us the total amount of light being produced.

Lux, on the other hand, is the number of lumens per square meter striking the surface, regardless of the frequency of the light and of the surfaces ability to reflect that light. This value will be distance dependent, and sums all light striking the surface, regardless of its source.

Perhaps the best way to think of it is that lumens tell you how much light is being produced, and lux tells you how much light is getting there.

[Dano]

I am trying to callibrate the white point and intensity of a high-end graphic arts LCD to match the percieved white point and intensity of graphic arts light booth. I have a spectrophotometer with a serialized white dome for light measurement. I can also adjust the intensity of the special D50 light to match the adjacent LCD screen. This particuliar light booth has special ballasts that maintains the white point when lowering the light intensity so there isn't a color shift.

My question is if I set my LCD to 140 cd/m2 what lux should I adjust the light booth to have a perceived match intensity? Once I get the intensity of the booth and LCD to match I will then measure the light booth's white point to use as the target white point for the LCD at 140 cd/m2.

Thanks.