This is a text file of the colour management
Ventura chapter recently uploaded and available
in this forum and in the Ventura forum.

Colour management

Ed Brown takes a closer look at the colour management 
dialogue box

Last month Bruce Lindbloom of Candela introduced us to 
what colour management is all about and why we need it. This month 
Ed takes us through the basic steps in using the colour management 
features that are available in both Corel DRAW! and Ventura Publisher.

As Bruce said, colour management is essential for the maintenance 
of colour fidelity across devices that can have widely different characteristics. 
Ventura has always been well endowed with colour capabilities. 
With the advent of version 5 of the Corel programs, there is now a 
common approach to colour management that encompasses the whole suite 
of applications.

If you look at the magazines you see in the newsagents, you will see 
that the printing ranges from your average newspaper quality through 
to printing that looks like a photograph. 

For the majority of users who wish to use colour, there 
are several shortcuts 

At the end of the day, I look at colour from a practical 
standpoint - it needs to communicate a message and has to be acceptable 
to the audience that will see it. For example there would be no point 
in printing TAGline! in a photo-realistic fashion and in 
the same way there is no point in printing an advert for an expensive 
perfume at the same level as TAGline! is printed. The difference 
at the end of the day is cost and acceptability to the reader.

Getting started

At the simplest level, using the colour management features 
in Corel programs is as easy as turning them on. In practice there 
is a little more to the equation than this but, for the average user, 
there is little need to go beyond the basic steps I'll discuss here.

If you're lucky, you will be able to select a monitor, printer and 
scanner from the list of devices already defined by Corel. If not, 
then you will have to go through the painstaking process of defining 
your own - but there are ways to cheat. The process is not as 
difficult as it sounds and for the majority of users who wish to use 
colour there are several shortcuts. If your devices aren't in the 
list, then you will have to define your own characterization and calibration 
for each one. You should start with monitor calibration. Although 
this does not seem the obvious place to start, all will become clear 
- read on.

You may be able to get by using the generic monitor, which seems to 
work quite well for everyday monitors. Beyond this a monitor can be 
calibrated easily if you have a few key values defining the white 
point, gamma, and chromaticity of your monitor under 'normal` conditions.

These key values aren't always easy to find, and you'll probably have 
to contact your manufacturer to get hold of them. However, once you 
have them you simply select 'other` under the monitor list, give it 
a name and plug your values into the monitor calibration dialogue 
and you're ready to go.

The more astute readers will have realized that last month Bruce pointed 
out that each device is different, and there is no such thing as a 
common set of values for every monitor of brand X. True, but this 
is the first point where the 'It's good enough` fudge factor comes 
into play. Those who want perfect colour will already have given up 
reading in disgust - the rest of us can get on with setting up 
our devices to give us reasonable results under most circumstances.

Interactive monitor calibration

If you are unable to get hold of the appropriate values 
don't panic - all is not lost. It is possible to set the monitor 
up interactively. To do this, select the interactive button in the 
monitor calibration dialogue and you get a pretty picture of a lady 
with fruit and flowers as shown opposite. You've seen it before haven't 
you? It's that photo thingy that was in the box. Quick, go and get 
it -  you're going to need it.

In this dialogue box you need to adjust the gamma, chromaticity and 
white point - that's the one measured in degrees Kelvin - 
to make the picture match as closely as possible to the picture. You 
can also use this to refine the values you used earlier to try and 
improve the screen representation. 

I found that working interactively was of little benefit unless you 
had more than 64K colours visible on screen as, below this value, 
there was little gain for the effort expended trying to improve the 
calibration. One thing to watch out for is that the preview picture 
does not change interactively, and you have to press the preview button 
to refresh the appearance of the picture. This has caught me out on 
a number of occasions.

There is little guidance to be given on how to manipulate the values 
in this dialogue box. My best suggestion is to go into it and make 
some sweeping alterations first to see how they affect the preview. 
Then cancel out of the dialogue and re-enter it and fine tune your 
setting. Again this is a case of applying the 'It's good enough` fudge 
factor and a bit of common sense.

Setting up your printer

Once you've got your monitor set up and calibrated to your 
satisfaction you can move on to your printer. Here life is much easier. 
At the end of the day the vast majority of people who will be using 
colour will have it printed on an offset printing press. A smaller 
number will have things printed out on desktop printers for proofing 
purposes.

Corel have realized this and have already defined  a number of common 
colour printers by manufacturers such as Canon, HP, Epson, Xerox, 
and Tektronix. A generic CMYK,  Inkjet CMYK, dye sublimation, thermal 
transfer, thermal wax, and a SWOP printer have also been defined.

The last-named is the one we are most interested in as this defines 
a Standard Web Offset Printer (SWOP) and this is an ideal starting 
point for most of our press work. The first thing we have to do here 
is to calibrate the printer for Under Colour Removal (UCR), Grey Component 
Reduction (GCR), and dot gain. As always there are some suitable default 
values.

If you want to define your own values this is perfectly possible, 
but make sure you consult your press-op about the values he experiences 
on his press. The values you enter here have a great affect on the 
output you get from the press-op at the end of the day.

I could go into all the details of what each of these things does 
and how they interact but, if you don't already know, then there is 
little point doing it at this stage. Suffice to say that they all 
control, in different ways, the amount of ink placed on the paper 
when your job is printed.

The next stage is to carry out a characterization on your printer. 
This involves outputting a sample sheet of colours and measuring the 
colours with a densitometer. Sounds difficult - it isn't, but 
you're not likely to have a densitometer lying around the office so 
you're back to doing it interactively on screen again. Here you need 
to output a test pattern and then make the colours on screen match 
the colours on your test pattern. By now you'll see why we started 
with making sure we'd got the calibration of the monitor right.

Calibrating your scanner

If you have one, you'll need to calibrate your scanner. 
This is the easiest task of all. You simply place the calibration 
target image - remember, the pretty picture thingy - into 
your scanner and scan it in as a TIFF file. To do this, use PhotoPaint 
and remember to turn calibration off when scanning, or you won't get 
a raw image scanned.

Next go to the scanner calibration dialogue and load the file you've 
just scanned as the target file and also the Corel supplied reference 
file CORELAR.REF. Click on the scanned target button and, when the 
image appears use the marquee tool to draw a grid round the whole 
of the image. When you release the mouse, the colour manager will 
automatically calculate the calibration for you and you can save it 
in a file for future use - easy!

Using it all

Now you've got a calibrated monitor, printer and scanner, 
you are ready to produce colour-corrected work. All you have to decide 
now is exactly how you want to use this new found power.

As you will see from the screenshot on the left, you need to decide 
how to apply the colour management. For the type of work you are likely 
to do - and here I'm guessing a bit, I'd like to offer some suggestions:

If you're using Pantone colours, do not use colour correction.

Stick with Fast as we've used quick and dirty methods so 
far.

If you're using a desktop printer, turn on Simulate Printer 
- otherwise don't bother.

Consider not bothering with colour correction - a lot 
of work will be good enough without it.

If you use colour correction make sure it is turned on at 
all stages.

Remember that there is one colour management system for 
all Corel programs and changes in one will affect the others.