optical brighteners in lustre paper - ok or avoid?

Started Jan 8, 2011 | Discussions thread
E Dinkla
Contributing MemberPosts: 540
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Re: optical brighteners in lustre paper - ok or avoid?
In reply to E Dinkla, Jan 11, 2011

Addition

From a discussion on the ArgyllCMS mailing list: The ColorMunki LED lamp doesn't emit any light below 430Nm wavelengths, the 380 to 430 measurements in the output files are actually copied from the 430 reading. There are issues with blue reflectance readings as well.

The Eye One comes in two variations: One without an UV-cut filter and with a lamp with UV content in its spectrum It will measure the absorbance (FBA and TiO2) or reflection (Barite etc) of UV light by whitening agents and the paper base and it will measure the reemitted blue light of FBAs. I have that model for measuring the spectral plots. Of course it will measure the reflection in the visible light range too. The TiO2 UV absorbance is at lower UV wavelengths than FBAs do and the energy is reemmitted in heat mainly so outside the other side of the visible spectral range.

The UV-cut version of the Eye One has the filter in front of the lamp and the sensor I think, so no fluorescent effect is created and measured. Colorimeters and spectrometers with a white LED lamp as the light source usually have no UV content in the light so are by nature UV-cut on the lamp. In profile creation programs there are often settings to compensate the UV-cut effect of a UV-cut spectrometer with an artificial FBA effect. ArgyllCMS does it the other way around, it simulates an UV-cut filter on the readings of a non-UV cut spectrometer. Given the diversity of FBA content in papers I find both tricky business but I think the ArgyllCMS method is more sound as it measures the FBA effect first before taking it out more or less. Opinions differ though.

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Ernst Dinkla

New: Spectral plots of +200 inkjet papers:
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm

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