Hi,
I may not have enough room to measure the CDs unless 8 m would be somewhat accurate?? I know I need a lux meter and I remember people building integrating Spheres for the cds? Can the Lux meter measure the CDs by itself? I don’t think it can.
I looked at some Lux meters and none of them went past 200,000 Lux. How does that Translate to cds?
Suggestions for a decent light meter and the possibility of measuring CDs in my apartment.
Budget $500 Max.
Thx
I am getting a flashback! There was a guy I believe from Europe selling these integrating Spheres that he made? It was a catchy name I can’t remember it.
I think I remember that guy’s name who was selling integrated Spheres..Maukka.. that was his username I believe.
From my experience, if your light throws less than 1km (250,000cd), 8m is perfectly adequate. If you want to measure a throwier light, you need more distance to not underestimate.
Integrating sphere, as the name suggests, provides a way to “integrate intensity across the inner surface of the sphere”, which gives you total output, not intensity. Lux meter, as the name suggests, is for measuring lux, i.e., intensity.
Lux and candela are different units that cannot be naively translated. Lux means “lumens per square meter”, which depends on measurement distance because light spreads out in area, while candela means “lumens per steradian”, which does not because light does not spread out in angle. Fortunately, the latter can roughly be interpreted as “lumens per square meter at 1m distance”. So if you normalize lux measurements to 1m, then lux and candela are numerically equal.
If you are out of room indoors, consider performing measurements outdoors or get a giant mirror to double indoor distances. It’s fine that a lux meter can’t measure more than 200,000lx, just increase the measurement distance and later normalize to 1m.
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Thanks QR.. for short.
So the Lux meter will measure the CDs so I can figure out the throw?
Integrating sphere that’s for lumens still a little confused.
Most of my lights are over 250 kcd, I have three that are over a million, several mid-range lights between 300Kcd and 550Kcd.
Lux meter quite literally measures just lux hitting the sensor. It is up to the user to determine the measurement distance and convert the reading to lux at 1m (equivalently, candela), via the inverse square law, i.e., multiplying by square of the distance.
Observe that total output of a light depends on its entire beam, while intensity depends on only the brightest part of the beam. So you can always figure out whether a device measures total output or local intensity by looking at what the device takes as input: the whole beam or just a point in the beam.
What lights are they? You will definitely need outdoor measurements for the >1Mcd lights. I own a 3Mcd light and take measurements more than 50m away.
To add on here, an integrating sphere is used in combination with a lux meter to measure lumens. The sphere integrates the light so that the lux at the measuring point does not depend on how the beam is shaped, only on the total amount of light.
To get lumens from an integrating sphere and lux meter, you’ll also need a calibration factor. The usual method is to measure a calibration light source with known output to get lux per lumen in a given sphere.
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