|Choosing correct colours|
What was the quote on the DTP Index page?
"I have got my image on the
This is one of several major problem areas of DTP image output. I have often suggested to students that almost two entire floors of a college site here in melbourne and around 130 Mac and Windows computers are dedicated mostly to learning how to create images or pages "predictably" for good quality output (highest quality comes later!). Respectfully I might say that design classes are the easy part (we can all get images on the screen even if the design is "erk!". Output is another thing all together).
At the outset the client should be questioned on the possibility of any components of a non CMYK colour job (colour copier, CD multimedia etc.) ever being used for CMYK pamphlets etc. If there is any likelihood of that happening then all complex drawing objects and bitmap images should be created with this in mind unless the client agrees to pay for the extra. When setting up the defaults for a page in any DTP program, the required page colour palette must be included. If this is done at the start then major problems should be avoided, yet repeatedly bureaus have to return jobs (and charge for them) or charge for expensive corrections.
|The image on the left shows
the CorelDraw list of colour systems. These are:
|Shown at the top of the
page is a Colour System reference book. With these a
colour can be nominated (by name or number) by a designer
anywhere in the world and then applied by a DTP operator
elsewhere, matching the reference with confidence.
The Pantone Spot Colour reference system colours are used when the printer will mix the ink to reference specifications. Each spot colour will be a special single colour on a press unit as apposed to CMYK that requires four press units trying to reproduce millions of colours. If just one small object is coloured with a Spot Colour on a CMYK page, then 5 colour plates will be output instead of 4. On the left is a sample one-colour Spot Colour job including a tint of the colour in the top panel. By selecting the solid colour and then applying a percentage value of it, the page can appear a little more interesting.
Process colours can be selected by any of the suitable colour systems listed or from a Colour Chart (2nd picture, top of page). This is an excellent way of selecting CMYK colours because the charts are printed using CMYK so all colours shown on the chart pages will print correctly. Each page shows the CMY and sometimes K in %, which can be entered into a programs colour picker.
Note: If you want all objects to appear as expected, do not use the "Convert All Colours To CMYK" option offered in some programs. Remember, if it cannot be printed in CMYK, the colour will change and often dramatically. The program used should list all colours used on the page via the Print option, indicating extra spot colours accidentally included. Of course an exception to this is when a known 5th colour is to be used as a Spot Colour (corporate colours, metallics, varnishes etc.)
|On the Intro to
CMYK page a bitmap image created using RGB
colours is shown after converting to CMYK. Many times an
artist is surprised to receive an expensive contract
quality colour proof from a bureau only to find that both
bitmap and drawing objects appear very differently to
what they planned or saw on their screen. Should you wish
to try the RGB sample, download
the 16.5Kb .ZIP file, uncompress and in PhotoShop change
the "Mode" to CMYK. Do not touch the image and
then toggle "Undo" back and forth to observe
Really we have just been talking about discipline. As soon as you create an object, colour the fill and outline options making sure that only one colour system is used for the whole page. The common Colour Systems are available in popular DTP programs by license. Rather than having a book to look at, the colours are listed by name and sample - but realise the colour samples will probably appear very differently on the monitor.
|Overprinting - the forgotten
Colour selectors will offer the option to Over Print each colour. Forgetting this option can create havoc. If ignored when it should be applied, the printer will face the impossible task of registering all image components and the page will look horrible, perhaps turning a clients promotion into a failure. Even subconsciously, the reader will ignore much of the advertised information on an ugly cheap advertisement and move on to other pages. (One of the proven sciences of Pagelayout and Design.)
When the Page Description Language (usually PostScript) calculates object relationships, an object below another will be ignored where the object above is to appear. This also applies to black text. If not corrected the colour plates will contain holes where ever the black will print. On the left you can view a simple scenario where this has occurred and unless trapping has been applied, the printing machine can only print every sheet accurately to a tolerance of perhaps a few hundredths of an inch leaving ugly gaps. Note that the human eye is offended far less by slight overlap (darker edges) than white or high contrast edges, and we will look at this in the Trapping page under construction.
Try the following tasks using a black and white printer to output the results. If you use A4 sized paper, set the job page size to A5 (half an A4) etc. so that trim marks and page info bars can be selected to print with the objects.
If extra colour plates print then you have a problem and should repeat the tasks. These steps will become second nature and eventually take little extra time. As many Drawing pages contain hundreds and sometimes thousands of objects, do not think you will be able to set object colours accurately after most of the job is finished, as we can with simple practice objects.
|CMYK Process Colours
|Pantone Spot Colours
|Pantone Process Colours
colouring - CMYK
Recent versions of painting programs such as Adobe's PhotoShop include various options that either warn the operator of Out-Of-Gamut colours or allow the selection of a closest CMYK colour. When working with an RGB image look at the View Menu for a Warning option.
If selecting colours from the Colour Picker, a warning symbol might appear suggesting that the chosen colour will not print using CMYK. The PhotoShop option is shown on the left and if the triangle appears, click on it and the nearest colour according to the programs look-up tables will be selected for you.
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