Difference between CMYK and CMYK + Grey?

[Okks]

Hello,

I would like to know whether someone has ever tried to print the same black and white image on a CMYK printer and on a CMYK + Grey ink to compare the results? While eveeyone says that the difference is clear, I can’t find any test online to see by myself how it really is...

For example, how would a black and white print on a PIXMA 6820 compare to one made on a PIXMA 8720 which contain this extra grey ink ?
Is the difference really visible?

 

[The Hat]

I would like to know whether someone has ever tried to print the same black and white image on a CMYK printer and on a CMYK + Grey ink to compare the results

For starters, CYMK printers are useless (Flawed) at producing quality B&W or Colour photos, so therefore adding in an extra grey colour can only enhance the photo a little more, but you still won’t get a decent print without black ink...

 

[andy_48]

For starters, CYMK printers are useless (Flawed) at producing quality B&W or Colour photos, so therefore adding in an extra grey colour can only enhance the photo a little more, but you still won’t get a decent print without black ink...

That's interesting. I thought the 'K' cart in both 6820 and 8720 is black ink. Is it ineffective in B&W prints?

 

[PeterBJ]

A colour inkjet printer also uses colours to produce grey. Here is a 200 x magnification of a light grey field from a greyscale printed with a Canon printer, I don't remember the model. The use of colours explains the problems with producing a neutral greyscale. Click to enlarge:

 

[mikling]

CMY can make grey. Printheads have a limited number of nozzles and patterns that they can print.
By incorporating a grey ink in the pattern the engineer can "save" themselves more patterns to be used by CMY. So by using a CMY with GY, they can produce MORE different colors because they have a limited amount of patterns from which to work with. So using these freed up patterns they can generate more even colors EVEN in colors, smoother gradations etc. You see in reality printers cannot print all the different colors they say they can produce. They hope we won't be able to tell and most times they are correct.

it depends on the image and the viewer and how picky they are. Simply having a Gray ink does not necessarily improve the color if it is not properly matched to the other colors....and that aspect is not easy.

For a decent set of CMY and K and a good profile, for most ordinary folks, they can't tell the difference. To answer your question.

Now gray inks are used on pigment ink printers for a different reason but if you are doing B&W with a photo pigment ink printer, yes, the gray is near mandatory for acceptable results.

 

[The Hat]

That's interesting. I thought the 'K' cart in both 6820 and 8720 is black ink. Is it ineffective in B&W prints?

In a CYMK 4 colour printer, the “K black” is not used for photo printing, but if the printer has 5 carts CYMKK then it is..

 

[Artur5]

In all logic, machines using only CMY for color shouldn’t be able to compete with models having an extra photo black cart. In real life though, looking side by side at test images that I printed with a IP3000 (CMY) and a IP4000 (CMYK), I can’t say which is which.

 

[Ink stained Fingers]

The situation is even slightly more complex than assumed. CMY dye are universally used to print on nomral paper, matte or glossy coated papers. Canon printers come with one or two black inks - a pigment ink which is solely used on normal and matte papers, and not even that if you turn on borderless printing or duplex printing on normal paper. An additional photo black dye ink is solely used with the paper selection for glossy photo papers. A CMYK printer - with CMY dye inks and a pigment black K ink - will use the pigmented black on normal paper, but switches to the CMY inks when printing on glossy papers. This makes comparisons not that easy , but you can assume these results - a pigment black is best suited for normal paper, you get sharp edges on letters and a good black level overall. If you select glossy paper but print on normal paper you'll see that the black level is not as dark as with the pigment ink and edges on letters are not as sharp. If you use a 5 color printer you'll see that the photo black with the glossy paper setting gives you a very good black level , visibly better and darker than with a CMY printer; those blacks mixed with the CMY inks typically show a color tint whereas the dye black produces a near neutal black.
The situation complicates fruther if the printer uses an additional gray/light black dye ink, you do not have access at all to the use of this ink, it is embedded in the driver how much and when this ink is used. The gray ink can be used to reduce the overall ink volume - the gray level of a non-saturated color can be substituted (partially) by the gray ink, an effect which is described here
https://en.wikipedia.org/wiki/Grey_component_replacement
The user cannot control how much of this effect is actually used by the driver. And the gray ink makes it easier to print more neutral looking B/W prints - with limitations since the gray ink itself is not completely neutral gray but needs to be corrected slightly by a color profile. The appearance of colors depend as well on the paper coating and not just on the inks themselves which gets corrected by some default settings in the driver or color profiles. So be aware that driver settings - duplex - borderless - glossy - matte - normal - influences how the driver uses the black ink(s) or not or one or the other

 

[The Hat]

I can’t say which is which.

It boggles the mind when we now have 12 cart printers doing the same job... All be it better.. but at what cost...

 

[Okks]

I did not precise it but PIXMA 8720 and 6820 both have dye ink, and CMYKK except 8720 have an extra GREY ink. So would the difference really be noticable between the two in B&W photos using greyscale printing mode? (No color used)