FNO - Fading in black/cyan/"photo" dye based inks

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Grandad35,

This is very informative. The saturation is more varied than I would have expected. Did you note any differences in the spectral distributions?

 

[Grandad35]

... Did you note any differences in the spectral distributions?

Here are 4 comparisons from the spectro. In each case, the red plot is from the photo paper sample and the black plot is from the "liquid ink" sample (the Lab values are for the photo paper samples).
1. The top left plots are for the paper itself to get a baseline. For the "liquid ink" sample, two layers of the same food wrap were added to the paper to measure the effect of the plastic on the distribution.
2. There is nothing on the cyan comparison that would not be consistent with a simple dilution of the color (from previous posts in this thread).
3. At first look, the magenta appears to show a spectral shift, with the longer wavelengths behaving differently from the shorter wavelengths. However, when the effect of the two layers of film is considered at the longer wavelengths, these differences can be explained in the same way as the cyan differences.
4. The yellow gets the same analysis as the magenta, except that the difference in light absorption at the shorter wavelengths is much more pronounced at the shorter wavelengths. This is consistent with what I saw on the samples and was reported by the spectro on the 9 color samples in a previous post.

... I began thinking about doing comparative ink tests with different papers, and wondered what you would think of that.

I think it is a good idea, especially since we do sometimes have something to print which we would prefer to do on other than glossy, like matte.

I agree that we should test several papers, printing only C/Y/M on each paper. Because you have bulk MIS CLI-8 inks available, they should be used for the paper tests. In the list below, you have the first paper and I will send you samples of 2-5.
1. Kirkland Professional Photo Paper - this will be the "baseline" paper. This should be one of the new packages with 150 sheets, and the same package should be used for all ink tests.
2. Ilford Classic Pearl - a matte finish swellable paper that has good longevity.
3. Ilford Smooth Pearl - similar to Classic Pearl, but with a nanoporous surface.
4. Canon Photo Paper Pro - a glossy, nanoporous paper.
5. Kodak Ultima - a matte finish, swellable paper.

Other common papers can be added if someone else is willing to supply them.

 

[canonfodder]

I do have a new package of the Kirkland Professional Photo Paper of the new 150 sheet quantity, and will set aside a large quantity as the "Baseline" paper. I will keep the paper in a zip-lock bag to reduce changes in moisture content as much as practical. Standard ink test samples will be prepared on that paper only.

In so far as possible, other papers to be used in paper comparison tests should have their dates given. This probably will be the purchase date in most cases. If no real date information is available, the best estimate may be used, but it must be identified as an estimate.

Other papers supplied for the paper comparison tests may be either one 8.5" x 11" sheet, or three 4" x 6" sheets. Send a PM to Grandad35 if you wish to suggest comparison testing of a paper which you could supply. He will give you information on the submission of papers for test.

 

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Looking at the spectra from Grandad35's tests, I would speculate that the internal reflections within the layer may be increasing the order of the filter. This is in line with the effect of cascading multiple similar optical filters whereas the final observed spectra is the result of those individual spectra multiplied together, resulting in sharper cut-offs. I would also speculate then that the yellow dye has a low-pass passband very close to 1. Multiple reflections would then only tend to sharpen the filter response resulting in a perceived increase in saturation. Having the passband close to 1 would also allow long wavelength light to pass, even through a concentrated bottle of the dye solution. Cyan's peak of much less than 1 would result in a bandpass that would pass less and less light as the path length increases, hence the opaque appearance of a cyan dye bottle

I also see sharpening of the filter response in the magenta PP color. As for cyan PP, it is difficult to compare unless the curve was normalized to the cyan "dye only" curve.

I can't take into account mordants, as there are just too many variables.