B&W printing, why color inks

As a B&W print is composed of different shades of black>gray>white, why are colored inks used in the printing process?

need something to mix with the black to get all them shades,unless you have a printer with white ink .

Equal amounts of cyan, magenta and yellow make grey. Black is mixed in to make the grey darker.

I've seen cheap printers not have a black cartridge and use equal amounts of colored ink to produce black/grey, but I assume that's not what you're talking about.

In a perfect printing world, and a pure b/w image, no colors other than black would be used.

And to smooth out gradients and transitions.

And here I was thinking that it might be profit driven...Nah.

It would depend upon the printing process used, I suppose.

BestVisuals wrote in post #11807574
I've seen cheap printers not have a black cartridge and use equal amounts of colored ink to produce black/grey, but I assume that's not what you're talking about.

In a perfect printing world, and a pure b/w image, no colors other than black would be used.

And this is the reason that I prefer the Canon iPF series of printers.
Of the 12 color channels in these machines, 4 are for specifically producing accurate B/W prints.
Black, matte black, gray, and photo gray.
Prints don't fade to a strange hue of red or green after hanging on a wall in the sunlight after a year or two.

UV rays are eventually harsh on B/W prints made from mixed colors.

Using black only ink wont get you the 256 shades needed between its self and the white of the paper. a printer with black only ink can only print in black. It can make a posterised grey by spreading the dots further apart to allow more of the white from the paper to show between but thats not going to look too professional is it. Black ink is intended to be used for text only.
I have never seen a printer with both black and white ink. Wonder if its ever been done? They dont call it a black and white picture for no reason.

JEC wrote in post #11812359
Black, matte black, gray, and photo gray.

Same setup in my old HP. But color inks are still used. Are you certain the Canons are not using any color inks?

Fading is another issue, but this is also why I love my HP 8750. I only print B&W to HP's own Premium Plus Photo Paper, a very high quality swellable type paper for dye inks. The paper encapsulates the inks and renders them more stable and highly resistant to fading. Tests from Wilhelm and Ardenberg prove this out.

Boerewors you'll have to take a look at the epson WT7900,hey it's why epson are the leaders in print technology.
The inks cost about £1600 a set.

ChasP505 wrote in post #11816455
Same setup in my old HP. But color inks are still used. Are you certain the Canons are not using any color inks?


Fading is another issue, but this is also why I love my HP 8750. I only print B&W to HP's own Premium Plus Photo Paper, a very high quality swellable type paper for dye inks. The paper encapsulates the inks and renders them more stable and highly resistant to fading. Tests from Wilhelm and Ardenberg prove this out.

Of course, even a print that appears to be Black and White to the human eye, may not actually be just that.
It's image specific.
As a person that takes pictures of very small things for industry, law enforcement, oil companies, paper mills..which sometimes includes picoliter size drops of ink, dye, and paint, I can verify that when I'm printing black -or shades of gray-.......it's really nothing but that.

When this isn't close enough:

Very cool equipment. Photography is NOT all about baby portraits and glamour shots. (Though I appreciate a good glamour shot!)