Difference between CMYK and CMYK + Grey?

[Ink stained Fingers]

You don't know what the driver is doing - you would need to do a microscopic analysis whether color inks are used together with the gray ink or not - as @PeterBJ is showing above. The driver option 'grayscale printing' does not necessarily mean that color inks are not used , it just means that a color image is converted into a grayscal image which gets printed. It could be that the driver is using just the black and gray ink for the normal and matte paper settings, but adds colors inks when using the glossy paper setting. The black and gray inks are not completely neutral, and the driver would correct that when using Canon papers.

 

[Artur5]

Whatever the driver does, I’m quite sure that it never mixes dye and pigmented inks, not even on plain/matte paper. If you’re printing a text page on plain paper, the machine uses solely pigmented black. If that page contains not only black text but also a graphic or photo in color, it uses pigment black for the text but only dye inks for the graphic. I guess that’s because pigmented and dye inks don’t mix well,

 

[Ink stained Fingers]

Whatever the driver does, I’m quite sure that it never mixes dye and pigmented inks, not even on plain/matte paper.

Yes, you are completely right, but the question is whether the driver renders gray levels just with one of the black inks (+gray ink) or uses additionally the color CMY inks to compensate tints in the black and gray inks or substitutes gray colors with a mix of CMY inks completely. It's not that the black inks don't mix well, the main problem is adherence either on matte or glossy surfaces - you could wipe off a matte pigment black ink off a glossy surface , so the driver uses those inks which are available for the paper type selected via the driver settings - dye black for glossy or matte black for normal/matte papers. The gray ink is suitable for both - matte or glossy papers.

 

[Okks]

Thank you all for your replies, it’s very interesting but I still can’t have a clear answer about my question, how would the difference be seen between two identical images printed using the same paper, same greyscale image printed in greyscale on two different similar printers like Canon pixma 8720 and 6820 which have exactly the same specs execpt one have CMYKK + GREY ink. I’m puzzled by all the reviews online praising expensive 12 inks printers with all the bells and whistles but failing to ever test the advantage of having an extra grey ink for black and white (maybe there is none and it’s just marketing?). Would love to see a side by side somewhere, but nobody tested this!

 

[andy_48]

I have an ip8750 (used predominantly and regularly for 4x6 snaps but up to A3+ occasionally) and an mg6650 (used for office documents, usually A4, and envelopes etc.). Both printers use the same 3rd party carts and inks from Octoink (which are great, BTW).

I am a rank amateur hobbyist (colour family snaps, mostly, virtually no B&W), have low expectations and am very happy with my setup. They're cheap to run, simple to use and relatively reliable. I used to run a pro 9000 mkII but found it to be overkill for my needs (it was huge and ate printheads if not used regularly).

I've just printed the same B&W image from Lightroom to both printers using Canon paper. Given my very poor expertise, I would claim the 8750 has better greys and the 6650 has more of a slight colour cast. Of course, I can't compare either with a pro printer but I'd be amazed if they could come close!

I've scanned them, for what it's worth, but I think the differences are clear.

It's not very scientific, but I hope this helps.

 

[PeterBJ]

@andy_48 It looks to me like your B/W prints have a strong dark green cast, unless this is caused by the scanner. A green cast indicates lack of magenta in the print. You could try increasing magenta probably 30 "units" ( units = % ?) in the driver settings. Here is a thread with a test image and a procedure to make the colour correction easier.

 

[andy_48]

@andy_48 It looks to me like your B/W prints have a strong dark green cast, unless this is caused by the scanner. A green cast indicates lack of magenta in the print. You could try increasing magenta probably 30 "units" ( units = % ?) in the driver settings. Here is a thread with a test image and a procedure to make the colour correction easier.

Thanks, I did wonder! I'd love to correct it but please would you repeat the link as I couldn't get it to work?

 

[stratman]

please would you repeat the link

In the advent PeterBJ is taking a well deserved nap, here is his terrific thread on color cast correction:

https://www.printerknowledge.com/threads/compatible-cartridges-and-colour-cast.10956/

 

[PeterBJ]

I looks like I made an error with the link. It should work now. Else it is also here: https://www.printerknowledge.com/threads/compatible-cartridges-and-colour-cast.10956/

 

[andy_48]

Wow! What a difference!

+30 might be a tad too much but I'll carry on experimenting. Thanks for the tip.