What is a photo black cartridge for?

ColourKid

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If you print photos (on photo paper) then you use the dye-based black (denoted K often times I gathered) instead of the pigment-based black (Bk). Now when does this "photo black" actually get used? Is it only for the parts of the photo where it is completely black ("true black")? Or does it also do some dithering to make other colours darker?

If it's only for the "true black" parts then I ask: what use is that? Since a photo is on average never truly black in 99% of the photo, it would use the colour inks (C, M, Y) for the majority of the print. In that case it might as well use a mixture of CMY to create black as well. That is, unless you photograph something way too under-exposed or if you are clipping your colours on the low-end, in which case it probably gives a better result to use a photo black for that.

So I suspect the printer uses the photo black also for making the colours darker. Is that true? How does that work? It just prints some black dots in between the colours? But would that not lower the quality actually since it cannot mix colours on the same spot on the paper? That is, you can only "dither" the true black in between the other inks, you cannot mix then since it will come out black anyway, which seems worse than just mixing the desired level of brightness using CMY. A grey dye-based ink then I would understand (which indeed some photo printers have) since you can use it to lower the brightness and then adjust it by mixing it with the colours. Or can printers also use lower droplets of black ink to truly mix a colour somehow (while it's still wet?) such that it becomes a colour instead of black? Can some expert reflect a little bit on this? Thanks!

BTW, I was a member of the Nifty Stuff forum before but apparently my account was lost, so thanks for having me back. :)
 

Ink stained Fingers

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I think it's not really possible to answer your questions just in general terms since different printers and technologies may do it differently - e.g. laser vs. inkjet vs. offset ....
Pigment inks in inkjet printers give you a better edge definition when you print black text on copy paper than dye inks which spread along the fibers in uncoated papers. So you have typical 5 color inkjet printers with a matte pigment black for text print and a dye black for photo prints on coated photo paper. Pigment ink photo printers have a matte black ink for matte papers - no glossy surface , and a glossy black ink for prints on glossy papers - both pigment inks.
The driver is transitioning the use of a dye black ink to a mix of CMY colors to make up dark grays probably at a point of 95% black luminance values in the image file. You easily could test that when you substitute the black ink with a clear ink in the black cartridige and print a gray scale ramp , you easily can see the range the transparent ink - in place of the black ink - is used. The use of gray inks makes it more complex - it's basically a secret of the driver doing the correct mix of colors with the gray ink(s). The driver will most likely do some of the GCR - gray color replacement and giving you smooth transitions from gray colors to nearly gray, slightly tinted colors.
https://en.wikipedia.org/wiki/Grey_component_replacement
 

ColourKid

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Thanks, seems the principle is a bit more complex than I thought. A test could indeed indicate what is happening for a given printer. Although for my MX870 that is currently a bit difficult as you would have to first purge all the old ink (also I don't have any transparent ink, is that the same as a cleaning cartridge or can that be used as such? -- Or just print with a empty cartridge, although I know it's not recommended, maybe I'll try to print one grey scale ramp when my photo black ink runs out -- or is that really not recommended?).

In any case, I do notice that the photo black (CLI-521Bk) in my printer is empty regularly. But that might also be because it uses the photo black for printing on normal paper when printing double sided using the auto duplex function (which it does because it prevents ink being see-through the paper, but I think it is stupid because the text is not sharp with the dye ink, which is even worse than a little see-through, and you cannot even set it to use the pigment black on black paper). I don't print that many photos so I think when I would not print duplex then the photo black would probably not be empty as much.
 

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I wouldn't recommend to 'print' without ink, you may use a cleaner instead, and it wouldn't make a difference for this tpye of test if it prints light gray or clear.
There are various reasons, and discussed frequently in this forum and elsewhere, why the photo black gets used up even if you don't print photos at all - you mention several of those, don't forget every cleaning cycle - photo black is not excluded , duplex printing etc. There is a reason why Canon switches inks for duplex printing, the paper is passing through additional rollers in the duplexer, and if you print with the pigment black you get more pigments transferred to those rollers - over time - than from dye ink, and then you may find tracks on your paper from these rollers contamimated with black pigments; it would not happen immediately, but after some duplex printing time, so the driver/firmware switches over to the dye black to prevent this.
So your printer is a multipurpose printer, and this leads to some compromises here and there, and don't forget the switch to dye black when printing borderless, this should prevent the build up of pigments from the overspray in the print bed. every company - Canon, Brother, Epson, HP may handle that differently, some don't let you print borderless at all on normal paper, but only on photo paper using dye inks only.
 

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Or just print with a empty cartridge,
I wouldn't recommend you to print anything without ink, and even using cleaner in your cart can damage the print head, so unless you got ink in all carts then don’t print..

Your printer is designed to use dye and a little pigment black when printing documents in Duplex, but your printer can use either dye or pigment depending on which Application you choose to print from.

An all-black Word document (1 Sided) will print with pigment ink but the same document will use an ink mix of dye/pigment when used in a PDF format, there’s no choice in the matter, so remember if you print without ink you risk burning out your print head..
 

ColourKid

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I wouldn't recommend to 'print' without ink, you may use a cleaner instead, and it wouldn't make a difference for this tpye of test if it prints light gray or clear.
There are various reasons, and discussed frequently in this forum and elsewhere, why the photo black gets used up even if you don't print photos at all - you mention several of those, don't forget every cleaning cycle - photo black is not excluded , duplex printing etc. There is a reason why Canon switches inks for duplex printing, the paper is passing through additional rollers in the duplexer, and if you print with the pigment black you get more pigments transferred to those rollers - over time - than from dye ink, and then you may find tracks on your paper from these rollers contamimated with black pigments; it would not happen immediately, but after some duplex printing time, so the driver/firmware switches over to the dye black to prevent this.
I didn't know about the roller issue when printing pigment black! I thought it was only because of the see-through problem caused by pigments sinking deeper into plain paper (I even contacted Canon about this and that was their explanation). What I do now a lot is manual duplex (just print all uneven pages of a document and then put it back in the tray and print all even pages :D -- no idea if that is also bad for the roller sticking, no issues so far).

So your printer is a multipurpose printer, and this leads to some compromises here and there, and don't forget the switch to dye black when printing borderless, this should prevent the build up of pigments from the overspray in the print bed. every company - Canon, Brother, Epson, HP may handle that differently, some don't let you print borderless at all on normal paper, but only on photo paper using dye inks only.
Indeed, I think when printing borderless it automatically uses dye, even on normal paper. I even gives you a warning when you do that. So with "print bed" you mean the waste ink bed? So pigments are worse for that?

I wouldn't recommend you to print anything without ink, and even using cleaner in your cart can damage the print head, so unless you got ink in all carts then don’t print..

Your printer is designed to use dye and a little pigment black when printing documents in Duplex, but your printer can use either dye or pigment depending on which Application you choose to print from.

An all-black Word document (1 Sided) will print with pigment ink but the same document will use an ink mix of dye/pigment when used in a PDF format, there’s no choice in the matter, so remember if you print without ink you risk burning out your print head..
Ok, got it! The ink cleaning solution is just a bottle I got for free when ordering some ink bottles. Never knew what to do with them. I guess you need to fill an empty cartridge with it and then do (deep?) cleaning cycles?

Wow, that's the strangest thing: you print from MS Word and you get 100% pigment ink, then you convert the document to PDF and it prints it mixed with dye??? Is that like a universal thing or do you have experience with the MX870, or other CLI-520/521 printers? Seems like something lower level must be going on though, since I assume the printer driver should be application-agnostic in principle. Is it a specific kind of addressing the printer driver that Word does different from a PDF programme?

BTW my experience is that printing from PDF is generally sharp (unless printing with auto-duplex). So I guess it mainly uses pigment ink still.

Now I suddenly got a major question: what about the auto duplex function on pigment-only printers? I was looking into the Maxify line as a possible replacement printer which I believe you and other people are quite enthusiastic about. That one can also do auto-duplex, so how does it prevent roller staining?
 

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You may use yellow dye ink instead, but you would have to rinse a black cartridge before you really can use it for such test, and rinsing a black cartridge would take a while until you get most of the black out of it. And I think such test would not give you much information really since you cannot change the driver/firmware internals. But you can do something else, print a grayscale ramp onto glossy paper, but with normal paper selected in the driver. The matte black pigment ink is directly visible on glossy paper , and you can wipe it off easily.
Roller staining - that's what Canon support explained to me some time ago when I directly asked them about the switch to dye black. There are different types of pigment inks , Epson specifically advertised their Durabrite pigment inks as fast drying and suitable for duplex printing. It is quite possible that the Maxify pigment inks are different to the one in the MX models - it's all more complex as it appears in the beginning. And to make it even more complex, Canon was and is adding some blue dye ink to the prints with the pigment black, this to neutralize the brownish color tone of that pigment black with some blue byprint. Other pigment blacks are more neutral without such compensating measures - not even all black matte pigment inks are alike.
 

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You may use yellow dye ink instead, but you would have to rinse a black cartridge before you really can use it for such test, and rinsing a black cartridge would take a while until you get most of the black out of it.......
Another possibility is to transfer a chip from a dye black cartridge to a yellow cartridge. See this instruction.
 

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Wow, that's the strangest thing: you print from MS Word and you get 100% pigment ink, then you convert the document to PDF and it prints it mixed with dye??? Is that like a universal thing or do you have experience with the MX870, or other CLI-520/521 printers
Your printer doesn’t have much say, whether it prints using dye or pigment, that is purely down to the Application you choose to use, I only used Word as an example because other Applications also mix and switch the two blacks..
BTW my experience is that printing from PDF is generally sharp (unless printing with auto-duplex). So I guess it mainly uses pigment ink still.
That’s why they use a mixture of both blacks, it still prints out very sharp..
what about the auto duplex function on pigment-only printers? I was looking into the Maxify line as a possible replacement printer which I believe you and other people are quite enthusiastic about. That one can also do auto-duplex, so how does it prevent roller staining?
The Maxify is a great all-round printer and has no difficulty with Duplex printing, I reckon it prints with a little less ink to prevent show through, but I am not certain of this, my last CLl-520/521 printer I converted to use CLl-8 carts..
 

ColourKid

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Your printer doesn’t have much say, whether it prints using dye or pigment, that is purely down to the Application you choose to use, I only used Word as an example because other Applications also mix and switch the two blacks..
Interesting that an application can decide that. I always thought it was more like that the application gives the printing contents to the driver and the driver determines based on what's best considering the specific printer hardware and what is printed how to print it.

The Maxify is a great all-round printer and has no difficulty with Duplex printing, I reckon it prints with a little less ink to prevent show through, but I am not certain of this, my last CLl-520/521 printer I converted to use CLl-8 carts..
I also had a CLI-8 printer before, the IP4000. I remember that the only difference between them was the use of a chip.

I posted some more questions about the Maxify in the thread: https://www.printerknowledge.com/threads/my-maxify-5350-is-on-refill-ink.11871/page-30 (Directed at @palombian but I think anyone with the printer could answer it. Anyway, a reply would be greatly appreciated. I need to buy a new printer soon actually to use at two locations.)
 
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