From Start to Finish
Over the last few months I've been looking into the jargon that surrounds desk top publishing, concentrating each month on a particular area. However, this month, in a change to the usual format, it's time to take a brief look at the entire printing process, from first ideas, to computer, to final printing press output.
Imagine your are creating a full colour leaflet, what would be the steps involved? To begin, any text, photographs, illustrations, logos and artwork etc. would have to be collected together, ready to be arranged on the computer.
There are many different software packages available for DTP, some for illustration and drawing, others for painting and photo-editing, and others for 'page-layout'. Which one you use depends upon the kind of document you are creating, and also on personal preferences. Usually individual 'elements' are created in a program best suited to them, then all these elements are arranged together in a 'page-layout' program. For instance, illustrations, logos and drawings may be created in a 'vector drawing program' such MacroMedia Freehand, CorelDraw or Adobe Illustrator, photographs and 'painterly' images may be created, edited and colour separated in a package such as Adobe Photoshop, text may be input and edited in a word processor such as MS Word, and finally all these elements would be arranged together in a page layout program such as Microsoft Publisher, Serif PagePlus, Quark XPress or Adobe PageMaker.
Any photographs required would be scanned into the computer. Usually, these are scanned from transparencies but if these are not available, the photographs could be scanned from photographic prints. Logos and illustrations could either be created directly on the computer, or could be scanned from original artwork, then edited and cleaned up in either a drawing program or photo-editor. When the artwork or photographs are scanned into the computer a file is created that represents the image, and this file becomes one of the elements.
Once all the elements have been created, they can be arranged together in the 'page-layout' program. Colour, text styles, graphic effects can all be set in this program, and the layout of the leaflet can be arranged too. To try out different versions, it is very easy to copy the page a few times, and create variations on each. Colours can be changed, new text entered, and if other photos are required these can be scanned again and imported into the layout.
Once a pleasing layout is achieved, examples can be output to a desktop colour printer, to check the layout when actually printed. However, it's worth noting that there will be differences between colours on screen, printed to desktop printers and the final printing press output. To check colours, a colour swatch book is required, choose the colour from the swatch book and enter the exact values for it into your program. The colour may look odd on screen but you know it will print correctly.
So you have all your elements together in say, Quark XPress, and you're happy with the design, so how does this transfer to the printing press? For the leaflet to be printed on the printing press, a printing plate is used for each of the 4 process colour inks used in most 'full colour' printing. One plate is required for each of these process inks, Cyan, Magenta, Yellow and blacK, known as CMYK. For the printer (the person, not the machine) to create these printing plates, artwork is required for each of the plates, and this artwork is output from the computer to a very high resolution printer called a 'imagesetter'.
Imagesetters can output text and images at resolutions from 1200dpi up to 5000 dpi, however for most printing work 2450dpi is usual, and this may be output to either 'bromide' glossy paper or clear film. The imagesetter does not output colour artwork or films, but outputs 4 films, each one is black and clear, but represents where it's associated colour (CMY or K) will be. The printer may ask for negative films, where clear areas on the film represent areas of ink in the final piece, and dark areas on the film represent clear areas on the final piece.
To have your document output to films from an imagesetter, the file can be sent out to a 'service bureau', where they will output your films for a charge. You could send them the file, and any linked picture files on a SyQuest removable drive or optical disk, or if the files will fit, a floppy disk. They will then output the films and return them to you.
You'll end up with four films, one for each of the Cyan, Magenta, Yellow and blacK process inks, and a set of these for each page. These films will only be black and clear, regardless of the ink colour they represent, so how can you tell how the image will look when printed, and if the films are correct? The service bureau can also offer a film proofing option, where each of the films is used to create a second film in the actual process ink colour, and when the four new films are overlaid and laminated together, they will represent in full colour the final finished piece. There are a few commercial types of this 'proofing', such as Chromalins or Matchprints, and the service bureau will usually have a particular favourite. Check with your service bureau.
At this stage you have a set of 4 colour films, a 'Chromalin' proof that looks good. These are then passed on to the printer, where the films will be used to create the printing plates required. This is done by exposing the light sensitive plates to light but through each film. Where the film blocks out the light, results in areas on the plate where the ink will be (if positive films) or areas where the ink will repel from (if negative films). For instance, the cyan plate is created by exposing it to light via the cyan film, and each plate is created this way in turn.
Once all the plates are ready, the press can be ready to run. Different printing presses can run different numbers of plates in one pass, i.e. a two colour press could lay two plates and therefore two inks in one pass, then the plates changed and the final two inks formed in the second run, thus requiring two 'run throughs' or passes. On a four colour press all the CMYK inks could be formed, and the leaflet printed in one pass. After all the inks have been printed, the piece is almost finished, apart from any cropping, folding or special finishes that have to be applied.
Briefly, the process involves:
- creating the leaflet in the page-layout program, including scanned images and photos,
- this is then output to the four CMYK films via an imagesetter,
- the films are proofed via Chromalins,
- the printer makes the printing plates from the films,
- the printing press then runs each colour in turn, and, almost finally,
- the leaflets are cropped and folded.
What I have not covered here are the more complex printing issues, but this does briefly cover the stages involved. Other areas such as imposition, where pages are organized so that many pages can be output in one pass, rather than a pass per page, and trapping, where items are slightly enlarged, shrunk or overlapped to avoid white lines between coloured items if there is any error in alignment on the printing press, will be covered in future articles.
Once again I appreciate any feedback or comments, and if you have any DTP-related questions please feel free to email me at the address below. Until next month happy DTP'ing!