[argyllcms] Re: More direct method of measuring FWA?

  • From: Ernst Dinkla <info@xxxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 27 Jul 2010 10:38:06 +0200

Graeme Gill schreef:

Ernst Dinkla wrote:
What factors are considered in the creation of an FBA algorithm is unknown to me but looking at spectral curves of FBA containing papers I would think it can not be as simple as a negative b in Lab value. If the absorption of UV is considered as well then another effect should be taken care of. The excellent TiO2 whitening agent, not an FBA as we know

I detailed how it works in my 2003 CIC paper:
<http://www.imaging.org/IST/store/epub.cfm?abstrid=22190>
I can send you a copy if you are interested.

Graeme Gill.


An interesting read. I skipped the formulae, there are better qualified people for that :-) It should give a sufficient representation of FBA influence.

I think that the straight line from the high point in the 650-700 nm through the lowest point between 450-520 nm may stay too high and straight beyond that lowest point at the short waves side, papers without FBA tend to curve more downwards there. It may be a range with less practical value for profile creation though. Where you verified the FBA compensation with different illuminants it could be interesting to measure an FBA free paper with a UV measuring spectrometer and apply the algorithm in that case too and see what is altered where no change should happen. Creating that curve from a third value between 450 and 700 nm will not work, papers vary too much on that range and I see no relation between that range and the lower than 450 nm range.

While reading I got the idea that the UV filtering of colorants could be taken into account.. To refine the estimation of the FBA influence it could be a route to explore further. I guess the UV filtering and fluorescence properties of the most common colorants is a shorter list than all the paper reflectancy data and it can be made more absolute if the software gets the ink brand name so use the data of that ink. Ink layer thickness being the unknown then with varying media presets.



--
Met vriendelijke groeten,      Ernst


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