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black and white inks for making digital negatives/prints?
On 10/27/2009 6:09 AM Lew spake thus:
You still have more or less full access to the usenet through Google groups and, possible, Yahoo. Thanks but no thanks. I'd rather not post or read at all than use Google's ill-conceived brain-damaged spam portal. -- Found--the gene that causes belief in genetic determinism |
#22
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black and white inks for making digital negatives/prints?
John Navas wrote:
On Sun, 25 Oct 2009 08:21:00 -0700, "Don Schmidt" Don red_1987 wrote in isition: "Matt Clara" wrote in message ... I know it's possible to purchase "B&W" inks comprised of black with shades of gray to replace the Cc,M,Y, cartridges in my old Epson 1270, but I don't know where to buy inks with a good reputation for this purpose. That's a new one to me; my inkjet printer produces shades of gray by the amount of black it uses to cover the area being printed, no matter how small the area. (The white is the paper being printed on) Gray inks produce a much superior result for critical work. For more information, see http://www.normankoren.com/makingfineprints4.html They're not "grey" inks. They're often called light-black and light-light black etc. They are weaker (diluted) versions of black ink. For the higher end inkjet photo printers carbon black pigments are used. Problem with carbon black and other "black" pigments is that they aren't black - they're usually a very very dark brown. So when they're applied at low density, they don't look very black. To overcome that, they add a blue/violet pigment (sometimes a dye) to make the black neutral when applied at different densities. They do the same with black for 4-colour (and more) litho press printing inks. All good so far, but carbon black and the available lightfast dark blue pigments had stability problems when used together in low viscosity aqueous formulations, and blue dye faded too fast for archival inks. AFAIK the first inkjet ink formulations to overcome this were Epson Ultrachrome K3 inks, with three "strengths" of black. The data explaining this together with example formulations is all there in US patents. So with neutral (or very close to neutral) at different densities, smooth tonality was limited by minimum droplet size, so having the ability to apply same minimum sized droplets of progressively "weaker" ink is an advantage, and bound to be more neutral than using CYM colours to achieve this. But some C,Y&M is still used with "neutral" black inks - it's not perfect, Droplet size isn't fixed, Epson Piezo heads can vary droplet size by varying amplitude and waveform of the signal (IIRC 8 sizes) HP have different sized thermal nozzles, so many more nozzles per head, and Canon are in-between, by having several different sized thermal elements driving each nozzle. The results are good. You can still see the droplets with a loupe. I can't with naked eye. |
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