How to measure light temperature

[Alan Thompson]

I have a light booth that has 5000k bulbs in it that I view my proofs in. My customer gets back to his studio and looks at the proof in his lighting. Is there a device that I can use to measure the color temperature of a particular setting? I remember a paper sales person having a small sheet of paper that would tell him if the light was 5000k or not when he held it in the viewing booth. Thanks, Alan

 

[meddington]

Re: How to measure light temperature

The GATF/Rhem indicator will diplay stripes when viewed under non-5000 K lighting and is likely what you're referring to. This is a cheap and easy solution to confirm color temperature, however, I almost always see strips, even in viewing booths that are measure 5000 K with light meters. ISO 3664 puts forth some requirements of lighting conditions, taking into consideration more than just color temperature (luminance/brightness, color rendering index, metamerism index, uniformity, ect). If you have an i1 spectrophotometer, there are a few solutions that allow for more thorough analysis of lighting ...i1 Share (free) , and BabelColor CT&A (inexpensive) , both allow for measurement for more than just color temperature.

 

[ASM]

Re: How to measure light temperature

Alan,
Yes the GATF/Rhem strips are useful but as Michael says, not the total solution. I'm in Australia but you have an excellent colour viewing company there in US called GTI GraphicLite and the people there (esp Fred McCurdy) are very helpful. They will explain the 50D or 5000K bulb/lamp will vary in colour response, spectral sensitivity etc from manufacturer to manufacturer, and also with hours of use over time, so if you want a really close match, your client needs to be viewing on the same device, under the same ambient conditions.
Minolta make a colour temperature meter; could also be useful.
G'Day