Digital BW, The Print

David: Thanks for the further clarification on meteramism.

John: I can understand your confusion, I had to do a lot of reading on Roark's website and MIS's website to get a handle on what the terminology means. Perhaps, although new to this, I may be able to help.

Briefly and simplisticly.

Producing a high quality monochrome image from a black only or a colour printer is not as easy as one would imagine.
Producing grey from black is done by using lots of small black dots. This method is called dithering and is not really what you would call high quality monochrome.
Producing grey from colour is done by mixing down inks from all colours to produce grey. This method can leave slight colour casts in the grey image.

A better approach is to use black and several shades of grey. MIS and others use a carbon based inkset. Carbon overcomes the problems with both dye and pigment based blacks. A RIP is required to control the mixing of the grey inks to produce a smooth tonal range.

Here is where it's easy to become confused with the terminology. Although the inks are all grey inks, they are placed in the printer in positions that were occupied by colour inks. Now it is possible to have inks labelled as cyan or magenta or yellow, but are in fact different shades of grey that are fitted into the cyan, magenta and yellow position in the printer. It is possible to be left wondering whether you are reading about the colour cyan ink or the 30% grey ink used in the cyan position of the printer.

In general when reading about Quadtone or Hextone inksets, the colour teminology refers to the shade of gray ink that is fitted into that colour position in the printer.
for example using UTFS quad inkset, the colour positions in the printer are occupied as follows:
Cyan by 30% grey ink
Magenta by 18% grey ink
Yellow by 2%  grey ink.

Now for the next confusing bit. Although the mixing of quadtone and hextone grey shades in the printer are normally controlled by a RIP, it is possible to use the Epson printer driver to control the ink mixing. After all, in normal use the Epson driver controls the colour mixing, so there is no reason why it cannot be used to control the grey inks fitted in those colour positions. Very often a Photoshop adjustment curve is also reqired to achieve a smooth tone from light to dark. Its important here also, to remember that any reference to a colour is actually a reference to the shade of grey that occupies that position in the printer. Using the Epson driver does not mean that there are any colour inks fitted to the printer.

But wait, there is more to learn.
There is another level of black inksets called "variable tone". These are also black inksets but some of the colour positions have grey inks with "toners" added to them. The toners can change the the greys from a cold grey up to a sepia print. Once again a RIP is the normal way to control the print, but the Epson driver can also be used here. The driver's "colour slider" controls are used, but they are used to control the grey smoothness and the grey tone, by controlling the grey ink or grey toner fitted in colour positions. There are no colour inks here either.

Now to the QTR used to control OEM inks.
These are colour inks. They are the Epson pigment inks as originally fitted to the printer. This is the "producing grey from colour" method by using the RIP to control the ratios of colour inks that will mix down to black without colour casts, right through from black to light grey.
As these inks are colour pigment inks they will be affected by metamerism. The output is grey, but the grey contains near equal amount of all colours.

The method of using OEM colour inks to produce grey is in no way similar to, or to be confused with the fixed or variable tone black inksets, like UTFS UT2, UT14 etc. The two methods are totally different, regardless of whether the ink mixing is controlled by a RIP or the Epson driver.

John: In your last post you mentioned controlling OEM inks with a RIP and controlling UT7 with the Epson driver. You must not confuse the UT7 black inkset with the OEM colour inkset. they can both be controlled by common drivers, but they are completely different inksets and methods.

I hope this has cleared things up a bit for you and anyone else new to the technology.

I apologise to those who think they are being taught to "suck eggs".

Paul Roark's website is a mine of information on printing with black inksets. Choose your printer, choose your inkset and then read about the workflow on Pauls site. He has also put together a comprehensive library of Photoshop curves and ICC profiles covering almost any combination of printer inkset and paper.

Cheers
Greg Nixon









--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "johngeyles" <jge@...> wrote:
>
> 
> Now I'm confused, David.   The information on the UT7 set says that it
> works well with the Epson driver:
> 
> http://www.inksupply.com/ut7_2200.cfm
> 
> Similarly, other respondents to my inquiry say that the QTR driver does
> a pretty good job with the OEM inks.
> 
> What am I missing ?
> 
> John
> 
>