Message
Re: Canson Infinity Platine Curve
2015-04-23 by brian_downunda@...
I also saw your Lula thread. I was concerned because I thought that the responses were a mix of helpful information, information that was too advanced for you as a new QTR user, Mac-specific information, and some things that were plain wrong, such as not printing the B&W target through QTR, although to be fair, the Image Science instructions are not clear enough IMHO (see my comments at the end).
So I thought I could offer a basic introduction to QTR for someone coming from normal colour printing. First of all, forget any reference to the Print Tool Program. This is a Mac specific program created to overcome some colour management problems in MacOS.
There are some similarities between colour printing and QTR printing, and some important differences. In order to explain these I'll first describe colour printing, even though you probably know most of this, so that I can then compare and contrast QTR.
Most people will print colour using the Epson printer driver. Although there are a range of driver options that you can select, it's a closed, black box. You can't change anything inside the driver as such. So if you're using Epson gloss or semi-gloss or matte, you can just choose the paper type in the driver and print. The next step is to get a better (more accurate) print by getting a custom colour (ICC) profile made for each paper that you use that better matches your printer. You turn off colour management in the driver and convert to the profile to print. This has several advantages. For Epson papers you will get more accurate prints and it also opens up the option of using non-Epson papers. It also means that you can use the colour profile to soft-proof in Photoshop, to get a more realistic preview of how the print will look. I assume you know all of this.
It's best to think of QTR as analogous to the printer driver. In fact, in MacOS it installs as a printer driver, but Roy Harrington hasn't been able to do this for Windows. However unlike the Epson driver, you can tinker inside it. And in fact you may need to. Whereas the Epson driver has a fixed set of (Epson) paper types, you are able to add additional papers to QTR, and as you discovered, you may need to if the one you want isn't there.
QTR uses "curves" to tell it how to print on a certain paper, and has two files that it uses to describe curves - a QTR Ink Descriptor File (qidf) and the quad file. The qidf contains the basic parameters of the curve, and if you have the capacity to create your own, you will first create a qidf that describes how much of each ink position to use and how to add toning and how much adjustment is needed to linearise the curve. So basic parameters. QTR then uses this to create the quad file, which is a precise description of how much of each ink position to use to print each luminosity value. You only need to the quad file to print, and if you ever use Jon Cone's Piezography inksets that's all you have. If you also get a qidf, then you will be able to tweak the characteristics of the curve and regenerate the quad file. So all this is equivalent to modifying and enhancing the printer driver in colour printing, if you were able to, but you're not.
As was mentioned on Lula, there are different folders for the quad and qidf files, and Windows 7 prefers that you use a special folder "C:\Users\(computer user name)\AppData\Local\VirtualStore\Program Files (x86)\QuadToneRIP to store files that you want to add to the install, rather than using the folders in Program Files, although you can put them there if you wish, but you'll need to use Admin rights to do so.
You can also create ICC profiles for QTR, as you do for colour printing. But here the workflow similarities get a bit murky. To create a profile, you print that 21x4 chart using QTR with the QTR settings that you will want to print with. Then it has to be scanned with a device like an i1 Photo and software that reads the density of the patches. QTR comes with a couple of supplementary programs that use this data to create the ICC profile. So creating the profile is fairly similar to creating a colour one.
The murkiness comes in whether you convert to the ICC profile for printing. Some suggest you do and some don't. If you convert to the profile then you soft-proof much as you would for colour, then you convert the file to the profile, and you save a the converted file as a duplicate. You then print this converted file using QTRGui. QTR doesn't do any profile conversion itself, which is why you must save a converted file for printing, rather than converting on-the-fly as you do for colour. (Note: These are Windows instructions - MacOS is partly different.) If you elect *not* to convert to the ICC, then you don't need to save a converted file, but you *must* choose the "preserve numbers" option in Photoshop soft-proofing, which will show you how the file will print without conversion.
The argument for conversion is that it gives a better screen-to-print match. The argument against is that conversion blocks up the shadows, which is true, but you can allow and adjust for that, up to a point.
Image science is offering only to create an ICC profile.
Jeff Grant is offering to create both a QTR curve and an ICC.
The Image Science instructions are a little confusing because you can also create an ICC for Epson ABW mode in the exact same way and use it in the same way with the same options for conversion and soft-proofing. So whatever software you will print with is how you print the 21x4 test chart.
(Note to advanced users. This is an introductory tutorial for a new QTR user. So I haven't dotted every i and crossed every t. Please don't bother to split hairs unless you really think I've made an error.)