Colour Calibration for OvationPro


OvationPro is capable of displaying CMYK images on screen using real time
conversion of the colours to RGB.

To achieve this it is necessary to have some means of specifying what RGB colours the CMYK inks produce. Traditionally this is done by specifying the inks.

The file Applets\ColSupp\Resources\Inks contains ink definition files. The format
is very similar to ink files on the Mac and in PhotoDesk.

However the results produced by OvationPro from inks files are not always as
good as they should be, and so it supports another mechanism for colour
calibration. This is a look up table of RGB equivalents for CMYK colours.

The look up table is made visible to OvationPro from an inks file. Look at
the ink file 'ink2' supplied with OvationPro, the last line is;

Table         Swop.dat

You will find inside the Applets\ColSupp\Resources\Tables directory a colour look
up table file called 'Swop.dat'.

The aim of this note is to explain how to produce your own colour look
up tables.

Two small exe files are provided.

MkCMYK.exe - when this is run it will create an approximately 2Mb CMYK sprite
file called 'CMYK.spr' in the same directory (which is why you don't want to run
it from inside an archive).

You should take this CMYK file and convert it to RGB using your favourite
program. When you've done this, save it in the same directory as the other
program MKTable.exe with the name 'RGB.spr'. When this program is run it will read
the RGB sprite and produce a new table called 'NewTable.dat'. This must be copied into the Tables folder inside the Colour supplement applet.

Finally you need an ink file which will use this new table. The one here
called 'NewInk' will do. Its role is just to call up the new table.

The new ink must be selected from colour choics and 'use inks to display
CMYK colours' must be ticked.

You can have as many ink files and tables as you like, and swop between them
from the menu in colour choices in OvationPro. You will however have to
change the names by hand.

Large CMYK images are slow to render, from OvationPro 2.54 onwards it is
easy to create proxy images for them to speed things up. The colours
produced by which ever colour correction system is in use at the time the
proxy is created will of course be retained as long as the proxy is kept
in use.



David Pilling