Hello! Roger Breton wrote: > The lamps these instruments are calibrated against are either PTB, NIST or > NRC traceable, within their respective uncertainty budgets, which usually > translate into fractions of delta Es. This reminds me of an idea I had some days ago... Wouldn't it be very handy to have a small very stable light source for reference purpose, that could easily (at low cost) be shipped between interested ArgyllCMS users? This could be measured with the best (most accurate) instrument available in the user base, to have a reference point. Maybe the results could even be used with the new correction matrices feature? My first thought is, that this should be based on a high CRI white LED with a very stable energy source (regulated/temperature compensated, lithium battery based), all packed in a durable box. I've read lately an interesting text on the inter-instrument agreement by KonicaMinolta: http://goo.gl/kgrr The conclusion "...it is not (or only within a specific tolerance) possible to compare absolute measuring results of different instrument types!" is once more disillusioning. So what do you all think, is it worthwhile to follow up on the "Poor Man's Reference Light Source" idea? Regards, Juergen