Using a single pigment with best UV blocking characteristics 4 refilablel cartridges

[Zero_Equals_Infinity]

As per the title: Refillable cartridge systems exist from 3rd parties (e.g. InkRepublic - R2880 CIS, 3880 CIS, 3800 CIS, R1900 CIS, R2400 CIS, R1800 CIS, R800 CIS, R280 CIS, 1400 CIS, C120 CIS) for Epson printers.

Question: Could a single pigment with excellent UV blocking characteristics be used in every refillable cartridge, and would it yield, (as I expect), smoother tonality, and a simpler process for creating a proper QTR curve. Note: I do not think that any steps would be skipped, (i.e. determine Dmax exposure, ink density for white at 0%, linearization curve), but I do think the creation of the curve would be simple and with fewer artifacts than occur when mixing and matching pigments with different UV blocking characteristics. Every nozzle (360 DPI * number of nozzels) could contribute to the overall density for each dot uniformly.

Has anybody explored or tried this idea?

Thanks,

Nick.

 

[pschwart]

As per the title: Refillable cartridge systems exist from 3rd parties (e.g. InkRepublic - R2880 CIS, 3880 CIS, 3800 CIS, R1900 CIS, R2400 CIS, R1800 CIS, R800 CIS, R280 CIS, 1400 CIS, C120 CIS) for Epson printers.

Question: Could a single pigment with excellent UV blocking characteristics be used in every refillable cartridge, and would it yield, (as I expect), smoother tonality, and a simpler process for creating a proper QTR curve. Note: I do not think that any steps would be skipped, (i.e. determine Dmax exposure, ink density for white at 0%, linearization curve), but I do think the creation of the curve would be simple and with fewer artifacts than occur when mixing and matching pigments with different UV blocking characteristics. Every nozzle (360 DPI * number of nozzels) could contribute to the overall density for each dot uniformly.

Has anybody explored or tried this idea?

Thanks,

Nick.

The key to smooth tonalities is to get maximum ink coverage, i.e. overlapping droplets to minimize clear film between droplets, and to minimize tonal jumps between droplets. The opposite of this is half-tones, where tonalities are an illusion created by the dispersion of black droplets. A single ink typically results in grainy images which is particularly unsettling in the highlights. What *does* work is to take an ink with good UV blocking and create dilutions for each ink channel. It was a giant improvement when printers started using inksets with 3 blacks, and 3rd-party inksets like Piezography take this even further by providing a dilution for *each* printer channel to maximize resolution and smooth transitions. The downside to this is you pretty much have to dedicate a printer for the monochrome inks, though this is a good strategy if you also want to make quality b&w prints.

 

[Zero_Equals_Infinity]

I expected that smooth tonalities required that clear film gaps be minimized or eliminated. That was actually why I was thinking that using the same ink uniformly for each dot was a good idea. Droplets would likely have a bell shape from centre to edge and overlap with neighbours to create a uniform appearance.

I can see how using only 1 out of 8 of the cartridges would create the clear film problem you are suggesting, but with all 8 cartridges contributing the same ink, the clear film problem should not manifest. Now instead of 1 black, there are 8, and if one wanted different densities that also could be accomplished with QTR by controlling each cartridge's contribution. That adds a layer of complexity to the mix, but may also offer some freedom to improve things.

Now let's consider another possibility. There are several good pigment choices which have slightly different UV blocking curves. Selecting to fill cartridges with those inks only is another possibility, as is mixing blends. For example, let's say you like the UV blocking characteristics of black, yellow, and cyan. You could use those only, and you could have a (K, K-Y, Y, Y-C, C, C-K, K-Y-C, K) set of cartridges which may be better suited to the UV sensitivity of the emulsion you are exposing. I think it opens up ways to roll-your-own to allow optimization in ways that were previously dictated by Epson. And yes it does essentially mean that a printer is now dedicated to alternate processing. At the very least, it allows the non-blocking pigments to be removed and replaced with something more effective. And don't forget, having the equivalent of clear film occurs if a pigment being used has an effective UV blocking value of 0 so this problem could be stopped in its tracks.

Am I missing an obvious fly in the ointment, and has anyone tried this?

Thanks for your thoughts, as it stimulates me to think more about it.

 

[gmikol]

Am I missing an obvious fly in the ointment, and has anyone tried this?

Thanks for your thoughts, as it stimulates me to think more about it.

Regardless of the number of black cartridges you have, a given gray tone will only use a certain number of dots per unit area. For a particular light tone on the negative (dark tone on the print) there will be relatively few very dark black dots, which will likely print ner pure white, and lots of clear film, which will obviously print at dmax. This has the potential to make this tone look grainy. If you're using multiple dilutions, as Epson does with K, LK, LLK, then this light tone might be using 3 times as many dots of the lightest color dilution of black. Now, there is more area coved with a lighter ink. So on a visaual scale, the print tone is the same. But on a microscopic scale, there is less difference between the areas covered with ink and those areas that are bare film.

This is basically what Phil was saying , but I hope it clarifies things a bit.

--Greg

 

[pschwart]

I expected that smooth tonalities required that clear film gaps be minimized or eliminated. That was actually why I was thinking that using the same ink uniformly for each dot was a good idea. Droplets would likely have a bell shape from centre to edge and overlap with neighbours to create a uniform appearance.

I can see how using only 1 out of 8 of the cartridges would create the clear film problem you are suggesting, but with all 8 cartridges contributing the same ink, the clear film problem should not manifest. Now instead of 1 black, there are 8, and if one wanted different densities that also could be accomplished with QTR by controlling each cartridge's contribution. That adds a layer of complexity to the mix, but may also offer some freedom to improve things.

Sorry, not going to work. Consider: QTR cannot make a cartridge filled with black ink print a gray droplet. If all your cartridges are filled with black ink, how are you going to print a lighter droplet immediately adjacent to a black droplet? Pick any color ink -- you won't be able to print gradations in tone without resorting to using more dispersed droplets, i.e. fewer droplets in a given area, resulting in a grainier image.
I have never tried loading all the cartridges with the same, undiluted ink, but my guess is you would end up with heavily posterized images -- all black and white with no midtones.

 

[Zero_Equals_Infinity]

Maybe I am being thick as a brick, it is always possible, but let me describe what I am thinking, and you can tell me why my interpretation is flawed.

Axioms (which is likely where my thinking runs askew):
1) A printer has cartridges (8) which apply ink with nozzles over a matrix on a substrate.
2) The smallest "addressible" space on that matrix can contain output from one and only one nozzle, (not continuous tone printing) for Epson.
i) But it can receive a greater or lesser density (i.e. number of drops) from a given nozzle hence altering the opacity at the location on the film.
ii) The opacity of an ink plus the density determine the number of photons per second which can pass.
a) Opacity of an ink is different for different wavelengths of light, (of which a narrow band in the UV part of the spectrum is important).
iii) If gaps exist between droplets, (clear film spaces), a limit to opacity exists which is equal to the percentage of clear film vs the ink covered area.

If each addressable space can contain only droplets which have a high opacity per drop for wavelengths of interest, the number of clear film spaces is minimized, and the ability to create a pure white area exists. Density and drop opacity then determine the number of photons per unit time which can pass for wavelengths which can effect the print.

Ideally, the opacity of a pigment would be uniform across the spectrum of light emitted from a given light source. In practice different pigments have differing opacities based upon the wavelength of a photon. Using several pigments which together provide a net high opacity over the sub-spectrum of interest is about as much as we can hope for, while eliminating the use of pigments which have little or no opacity in the sub-spectrum of interest reduces the clear film problem to allow a full tonal range to be created on the print.

Hence, substituting pigments which have significant opacity for those which do not should provide the means to realise smoother tone transitions by eliminating clear film spaces.

Assuming that pigments can be mixed in a given cartridge, and that mixed pigments are reasonably well distributed and remain that way, a mixture that covers the sub-spectrum of interest as uniformly as possible would be ideal. Then a uniform opacity over the sub-spectrum of interest could be realised with the benefit of smoother tonal transitions on the print.

If I have either made axiomatic omissions or errors which are substantive, or if my logic is substantively incomplete or in error, please let me know since I would prefer not to spend time and money exploring this if the outcome is no better than what I am able to realise with the existing set of pigments.

Sorry if that was long-winded, and I hope it is clear enough. As usual, my thanks in advance for your patience and assistance.

Nick.

 

[pschwart]

i) But it can receive a greater or lesser density (i.e. number of drops) from a given nozzle hence altering the opacity at the location on the film.

You are counting on overprinting locations on film to deliver a range of densities. That means you won't be using black but a dilution or some other color that has less UV blocking. I don't know if the native driver or QTR lay down ink this way. Maybe the dither is sufficient to make this appear to be the print methodology even if it is not.

I do know that some practitioners of black-only printing developed methods of making relective prints using 2 and 3 channels of MIS Eboni ink (the goal being to print with 100% carbon ink). The paper prints looked pretty good (better than black-only with 1 cartridge), but there is substantially more dot gain on paper than film. More channels with a range of UV blocking is still going to produce a smoother tone ramp. Sounds like you have some testing to do Get some refillable cartridges, fill them all with yellow, cyan, light black or whatever you like (the QTR ink calibration page will be helpful) and start profiling.

 

[Zero_Equals_Infinity]

I love experimenting.

I may have to contact the author of the QTR software to get his input. That would be a wise thing to do before proceeding further.

Thank-you,

Nick.