See http://www.cis.rit.edu/research/mcsl2/online/cie.php Under CIE Standard Illuminant Data, they have A, D65, F1-F12 sampled in 5nm increments, either on a webpage or in Excel format. If you graph F1 and F5 in Excel, you'll see they are very similar, but slightly different. Same general shape and peak points, just slightly different amplitude here and there. Also see http://en.wikipedia.org/wiki/Standard_illuminant#Illuminant_series_F I prefer the home-made Excel graph from RIT's data, as the wikipedia graph doesn't quite do it for me. Someone may correct me, but comparing the two, I don't think you will see a practical difference using F5 or F1 in ArgyllCMS. I think the other variables will make the difference between the two spectrums inconsequential. It seems common practice to include a few of the Fx's but not all of them. A few other programs that I use that allow you to choose the illuminant don't have them all, which furthers me believing there's not a real-world difference between the types they group together. Obviously a bigger difference when you jump categories, F1-6, F7-9, and F10-12. On Fri, Nov 22, 2013 at 8:40 PM, Stephen T <stwebvanuatu@xxxxxxxxxxxx>wrote: > Hello, > > Both F1 and F5 are "standard" fluorescent daylight illuminants. > F1 has CCT=6430K and CRI=76. > F5 has CCT=6350K and CRI=72. > What is the difference? > > F5 is widely available in ArgyllCMS. F1 is not. > > I have some compact flourescent bulbs which are 6500 K Cool daylight and > CRI 80. F1 could be a better match than F5 for these? Are the spectra of F5 > and F1 very different? > > P.S. I do not have a spectrometer to measure the bulbs. > > Stephen. > >