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Author Topic: Fluorescence of dye colorants  (Read 2219 times)
Czornyj
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« on: March 30, 2014, 02:56:47 PM »
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My client recently brought a print from Epson L800 dye inkjet printer, that had visible green tint in grayscale. I measured it with my i1Pro2 in M2 and M1 modes, but to my astonishment I noticed, that the sensor was reporting magentish tint (+2,5 a*). I came to the conclusion, that C and Y dye inks must exhibit some fluorescence, and the M1 simulation in i1Pro2 doesn't take into account the fluorescence of colorants.

Is anyone familiar with similar issues? Can you confirm my colorant fluorescence hypothesis? Did anyone had any luck with resolving such issue with a different sensor, like Konica-Minolta FD7, Barbieri SpectroPad, i1 iSis, or Spectrolino with D65 filter (I still should have one in basement)?
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Ernst Dinkla
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« Reply #1 on: March 30, 2014, 03:20:55 PM »
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Dyes that have a fluorescent effect is possible. Dyes that filter on the fluorescent effect of the paper OBAs, positive or negative, is possible too. I did not encounter both being without dye ink printers for a long time but what I did experience is the effect of bronzing in B&W target prints on the Lab ab results measured with an i1Pro (UV enabled). The usual 45 degr optics in spectrometers can get influenced by bronzing. The only reference to that effect I found in a Datacolor document.

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Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
January 2014, 600+ inkjet media white spectral plots.

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Czornyj
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« Reply #2 on: March 30, 2014, 03:52:29 PM »
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Ernst, I did measurements using M1 (D50 simulation) and M2 (UV cut simulation) - it resulted in the b* coordinate change, but the a* coordinate was virtually the same in both modes, so I suppose it was related to colorant rather than paper fluorescence. My wild guess is that i1pro2 in simulated M1/M2 mode measures the fluorescence induced by UV emitter, but only assumes that it comes from paper OBA. Thanks for the interesting information about bronzing issue in 45/0 spectrophotometers, I wasn't aware of that Wink

Dyes that have a fluorescent effect is possible. Dyes that filter on the fluorescent effect of the paper OBAs, positive or negative, is possible too. I did not encounter both being without dye ink printers for a long time but what I did experience is the effect of bronzing in B&W target prints on the Lab ab results measured with an i1Pro (UV enabled). The usual 45 degr optics in spectrometers can get influenced by bronzing. The only reference to that effect I found in a Datacolor document.

--
Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
January 2014, 600+ inkjet media white spectral plots.



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Ernst Dinkla
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« Reply #3 on: March 31, 2014, 03:06:06 AM »
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Well it was the complimentary colors you mentioned; green seen in the grey and magenta measured in the grey that made me think it could be bronzing. The spectrometer reading shifted by the bronzing, the profile compensating for the magenta reading and delivering a green bias in the printed grey. Quite like I observed once.
Fluorescence usually shifts shorter wavelength energy to lower wavelength energy, how that would work out on the ink hues you mentioned I do not know but I think the cyan is then the most likely candidate for fluorescence and not the yellow. There is some literature on the web about dyes masking paper OBA effects and fluorescence in dyes themselves.

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Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
January 2014, 600+ inkjet media white spectral plots.
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Czornyj
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« Reply #4 on: March 31, 2014, 04:21:24 AM »
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That's correct - in fact Canon uses green pigment ink to counteract bronzing. But in this case the print was made with dye inks, and I always associated bronzing effect with pigment particles.

I'll try to check what's going on with Spectrolino that has physical UV cut, D65 and Polarising filters.
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Alan Goldhammer
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« Reply #5 on: March 31, 2014, 08:23:10 AM »
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Fluorescence usually shifts shorter wavelength energy to lower wavelength energy, how that would work out on the ink hues you mentioned I do not know but I think the cyan is then the most likely candidate for fluorescence and not the yellow. There is some literature on the web about dyes masking paper OBA effects and fluorescence in dyes themselves.
Not necessarily, depending on the molecular structure of the dye lots of different colored molecules can exhibit fluorescence.  One of the most common dyes used in biomedical research is fluorescein.  The di-sodium salt is yellow and is commonly used in doing 3-D retinal scans.  I had one done about six weeks ago. Back in the old days when I was doing protein research we commonly used a fluorescein derivative to label proteins of interest.
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