Calibrating Light Meters

[Hawaii596]

Trying to Identify standards to cal light meters like the simple Extech Easy View and similar.  I found a Gamma Scientific RS-10A source with RS-1 monitor.  Anyone familiar with light meter cals and/or these standards?  Need to find a low cost method.  I found in GIDEP the Hoffman Engineering equipment.

I'd appreciate any low cost brand name info on how what standard(s) would be adequate for some of the simple light meters.

[scottbp]

We use an International Light IL-1700 research photometer with SED033/Y/W detector for our standard detector. The light source is a 24V 30 watt quartz/halogen standard lamp from Hoffman Engineering, which has been "calibrated" by Hoffman Engineering to find the voltage at which it produces a color temperature that the photodetector is most sensitive to. Our test setup is a 4 foot long rectangular light proof box lined with black felt, with a hole in one end of the box for the detector, and the lamp at about one yard away inside the box. To vary the intensity, we move the light source towards or away from the detector, instead of varying the voltage to the lamp- that way the color temperature stays constant. This setup is quite crude, though. The modern way of calibrating light meters is to use an integrating sphere (a hollow ball with a white reflective coating on the inside) in conjunction with a set of filters to vary the intensity, it has something to do with the way the photodetectors respond more accurately to a uniform spread out source of light as opposed to a point source.

Their website is intl-lighttech dot com, and they even have a light measurement handbook for download.