MrTwist1
Well-Known Member
haha u beat me to it.
Spectrum shift in COBS due to dimming/current reduction....
- Thread starter thetr33man
- Start date
Abiqua
Well-Known Member
Did anyone actually read the paper: http://www.lrc.rpi.edu/programs/solidstate/cr_effectsofdimming.asp
1st it compared Red Green Blue AND and white...which had the narrowest range of chromaticity shift out of the 4 diodes tested in this paper...but the white isn't what is being used in Vero/CxaCxb....
before moving on.....green had the worst shift, red's shift was due to it Tj temp [not a surprise and why sanding heatsinks was even necessary....not with Cob's though...Supra proved that over and over again.... ] blue wasn't terrible and white had the least amount of shift....
Just a few lines down is a study on White led and PWM vs CCR dimming...done just a year earlier and [really needs to be updated 11 years later....]
http://www.lrc.rpi.edu/programs/solidstate/cr_chromaticityShifts.asp
and it shows a much smaller if not miniscule shift according to the CIE 1931 Chromaticity
This whole conversation needs to be restarted imho....it is important topic no doubt...... but to say chromaticity shift is occuring based on the suggestions of the 1st paper, without at least referencing the 2nd is just cherry picking the data and I am still hanging up on where there is a comparison to correlate? ...
Edit: in fact, it seems to fit within the MacAdam 3 step let alone 4....pointing to a chromaticity shift that is guaranteed in the Datasheet according to what step your diodes might be...[aka 2 or 4 step is most common]....I would say this pokes holes in the shifting theory...
search StarDustSailor too, there were a few succint posts covering this on the proddings from Guod above I believe, but you might have to dig back about 2 years....
1st it compared Red Green Blue AND and white...which had the narrowest range of chromaticity shift out of the 4 diodes tested in this paper...but the white isn't what is being used in Vero/CxaCxb....
before moving on.....green had the worst shift, red's shift was due to it Tj temp [not a surprise and why sanding heatsinks was even necessary....not with Cob's though...Supra proved that over and over again.... ] blue wasn't terrible and white had the least amount of shift....
Just a few lines down is a study on White led and PWM vs CCR dimming...done just a year earlier and [really needs to be updated 11 years later....]
http://www.lrc.rpi.edu/programs/solidstate/cr_chromaticityShifts.asp
and it shows a much smaller if not miniscule shift according to the CIE 1931 Chromaticity
This whole conversation needs to be restarted imho....it is important topic no doubt...... but to say chromaticity shift is occuring based on the suggestions of the 1st paper, without at least referencing the 2nd is just cherry picking the data and I am still hanging up on where there is a comparison to correlate? ...
Edit: in fact, it seems to fit within the MacAdam 3 step let alone 4....pointing to a chromaticity shift that is guaranteed in the Datasheet according to what step your diodes might be...[aka 2 or 4 step is most common]....I would say this pokes holes in the shifting theory...
search StarDustSailor too, there were a few succint posts covering this on the proddings from Guod above I believe, but you might have to dig back about 2 years....