- This topic has 13 replies, 3 voices, and was last updated 1 year, 1 month ago by
.
-
Posts
-
Hi !
I’ve a problem of reading differences between my I1 Pro 2 and I1 Display Plus. In fact I calibrated to D65 with my colorimeter using my spectral correction I did for this display. I experimented the E illuminant with my I1 Display Plus and I wanted to see the result spectrum to check if all peaks were at same level. And I saw that the peaks weren’t at the same level especially the blue one. Naturally I checked the xy values and even if my colorimeter gave me ~0.3333 ~0.3333 the spectrophotometer gave me values less than 0.330 0.330. Where is the problem located ? Because if I have a corrected colorimeter using a smoothed CCSS that doesn’t give me the same values as the 3.333 res spectrophotometer, it is rather frustrating. I’m thinking about the 3.3333 nm res sampling being put into the unsmoothed CCSS as a 3 nm res. Does the rounding from the CCSS implies the 3.3333 even if it is registered as an integer of 3 ? The problem doesn’t occure on my AMOLED as much as my White LED monitor.
Copy paste from other web
If an EDR/CCSS truly matches the behavior of some display (or light source in your case), the measurement error with an i1d3 applying that EDR/CCSS to that display is caused by a missmatch between what firmware says about spectral sensivities and actual spectral sensivities of that device. A “non correctable error” unless you create a custom 3×3 matrix using other device as reference.
Maybe i1d3 spectral sensivities stored on firmware near the edges of spectral range were not so accurate vs actual sensivity values, given that you are using an equal energy illuminant rather than a display with peaks focused on the typical blue green and red near humen sensivity peak.
Or maybe it’s an app bug. You should report this to ArgyllCMS mailllist but if I had to bet … it seems related to the limits of CCSS correction explained on the previous sentence on the extreme case of illuminant E.
Calibrite Display Pro HL on Amazon
Disclosure: As an Amazon Associate I earn from qualifying purchases.Thank you for the input ! In fact my hypthesis about the res of 3.333 nm is registered as 3 nm in the CCSS is true. I tried to do a correction matrix and I got the same measured white point with the I1Pro 2 and the Display Plus. So I think there is a problem with CCSS based correction in ArgyllCMS libraries. I will try to see how to report this bug. Is there a way to smooth the I1Pro 2 ti3 datas ? It’s to increase the blue readings accuracy.
matrix = make the test device measure the same as reference… this is the point. But it is not “portable”, you cannot distribute it for other people’s i1d3, it’s just for yours.
ccss = relies on firmware spectral sensivities matching actual spectral sensivities in device + maybe some rounding errors due to method. But you can distribute.
I do not thing that this is an CCSS error, but device’s. its about QC in the extreme regime of illuminant E, and as you said its about 0,0003 xy wich should be very small in dE00
That was rather xy = 0.003
In fact I obtain a match between a Colorchecker and my monitor with CCSS CIE 2015 10 deg + I1DPlus 2015 10 deg than with a matrix profile where only the I1 Pro 2 is set to 10 deg 2015 observer. So I think I’ll stay with a smoothed CCSS and let the software do the rest. I think I gonna try to calibrate with the new CCSS I smoothed with the rounded values rather than the recomputed 3.333… I did last time.
By the way, is it normal that an LED backlit monitor calibrated to an E illuminant has a peak in the blue ?
By the way, is it normal that an LED backlit monitor calibrated to an E illuminant has a peak in the blue ?
IDNK what you mean, please elaborate.
If I calibrate an LED backlit monitor to the E illuminant, will the blue peak be higher than red and green ones ? So is it normal or the blue peak has to be at the same level if we use a spectrophotometer ? Is it clearer ?
If I calibrate an LED backlit monitor to the E illuminant, will the blue peak be higher than red and green ones ? So is it normal or the blue peak has to be at the same level if we use a spectrophotometer ? Is it clearer ?
If you calibrate to some match Illuminant X, that SPD will be weigthed vs std observer and get some XYZ or Yxy coords
Then you calibrate white to those xy coords and depending on display SPD it will have different peaks depending on each display technology.I thought after reading your thread for 1st time that you had some simulation of illuminant E and you wanted to measure that simulation, which is a different task than you really asked for.
If because of whatever reason I cannot imagine right now, you want to get a whitepoint where the peaks of each channel are equal (more or less):
-get a CCSS of that display
-import into Excel or equivalent app.
-find max peak on each channel and teh mas between them.
-scale the non max spectral series so their peaks match the channel with the highest peak
-compute integral over visible wavelengths of the sum of scaled R+G+B channels multiplied by each “-bar” function. If wavelength step is 1, you could use Excel SUM funcion.
Resulting XYZ is the target white you try to aim.
But as said before I do not find what use has this…OK, it remains the same principle as targeting a D65 whitepoint, an E illuminant metamere isn’t always all peak at the same levels. So it’s totally normal
What exactly did you measure? How does the spectrum look like? Illuminant E is theoretical a flat line. I don’t think an actual light source exists which is able to produce a flat spectrum.
Display spectra are not flat and cannot be made flat just by changing RGB channels. Equals peaks maybe, but why? Here is an example which displays D65 white even if the blue peak is considerably higher than the other two.
Here is the spectrum of the White LED LCD calibrated to the E illuminant and CIE 2012 10 deg CMF. The blue peak is rather high compared to the green and red ones. But as it has been said before, the 0.3333 0.3333 xy isn’t all peaks at the same level concidering the used CMF.
There is an infinity of spectra that produces 0.3333 0.3333 under any CMF. This is how metamerism works.
