9. Dummy: Rough layout which shows how the final publication will look like in appearance. It may not contain the entire text, but show the position of graphics, text matter, layout, size, headings, title pages, half title, contents, page no etc. Based on the dummy only the pages will be assembled and printed.
10. Dimensional Stability: Ability of paper under print and other substrates used for processing the printing plates to retain their exact size –without getting expanded or shrunk. They should retain the dimensions even when affected by changes in moisture content or humidity in the press room atmosphere, during the printing process, varying temperatures or even the passage of time. The Paper and films used for printing should maintain their original dimensions with a high degree of dimensional stability when multi colour perfect registered jobs are printed.
As for the Paper, low dimensional stability may change size slightly during the printing process thus causing mis register. Therefore the paper used for the multi color printing is conditioned to the room temperature for few days before commencing printing to maintain dimensional stability.
As for the films processed in studio for preparing the printing plates, those that have low dimensional stability may change size and cause mis register (from the plates prepared from those negatives/positives).
While the glass films have greater degree of dimensional stability, some of the film bases are not, and therefore the process department should be careful in selecting appropriate films to maintain dimensional stability. Various substances used as film base include Acetate base, Tri acetate, Polyester, Cronar, Mylar® etc, some of which are the proprietary products of some of the photographic firms.
The dimensional stability cause problems in two areas in printing. If the press room is not air conditioned, the problem on account of dimensional stability can cause severe register problems when multi colour printing is carried out. Cotton fibers which is the main constituent of the paper, swell or shrink in diameter during extreme weather conditions and variation in the moisture content in the air. Since most of the fiber in the sheet are aligned in the machine run direction, absorption and de-absorption of moisture by paper causes the change in cross direction as the paper fibers when absorb water expand primarily in width, but only slightly in length. Uneven dimensional changes cause undesirable cocking and curling.
This is the case when the films used for making plates are processed. The film substrates which form the film bases show a high sensitivity to variations in temperature and humidity. Despite numerous layers and coatings associated with the emulsion layer, the base generally accounts for the vast majority of dimensional stability. For example the thin films with Acetate bases reportedly have less dimensional stability than those with Polyester or Easter or Mylar base films, some of which are proprietary products of some of the photographic firms.
11. Desktop Publishing : Called DTP this is fast developing technique to print jobs of lesser quality and quantity jobs as this process requires no plates or blocks or types to render printed image. The copy for the print is neatly typed, assembled with graphics etc and used as original and printed like automatic photo copier. In short this can be called a glorified photo copier or a duplicator. This printer can be directly connected to computer to feed the data or assembled copies that require to be printed. Many printing companies use desktop publishing equipment for their smallest orders because it is much cheaper than using large mechanical presses for small quantities and their delivery time to the customer is very short. The typical desktop publishing system consisted of a personal computer, a printer, and the appropriate software to carryout the entire operations.
12. Dropout : Halftone dots or fine lines eliminated from highlights by overexposure during camera work. This is sometimes done by adjusting the exposure time in the process cameras when the negatives or positives are taken. This technique is adapted to enhance the appearance of the originals which contain flat tonal values.
13. Digital Printing: In one way this can also be grouped under DTP family. This is a process in which the image is created on the computer and transmitted directly to the output device i.e the printer. No pre press operation including making of negatives from thee composed matter , assembling etc, or plates are required. The prints are taken combining both text matter and the photographs including the colored ones, using Liquid ink-jet, wet/dry toner systems, solid ink-jet, thermal-transfer etc. The equipments also aid in saving space, cut down production time and most suitable for small and immediate jobs. Determining when to use digital printing instead of a traditional printing process is highly dependent on the number of prints needed as well as the production speed of the output device.
One important advantage of Digital printing is the possibility of printing variable Data using information obtained from the database or external file. The texts and graphics can be changed on each sheet without stopping or slowing down the press. For example, personalized letters can be printed with a different name and address on each letter. Digital printing is also a very flexible process that provides a great opportunity for creativity as it allows the press to make the desired changes without prepress operations. By digital printing even big sized posters of only few copies can be printed in the shortest time provided the press owned a digital printing machine which can take paper from the reel to print the copies. The digital printing machine normally uses only four colour cartridges with whose combination the multi colour printing is carried out.
14.Dry Offset : Printing on Offset machines using Photo polymer base plates with relief images (like in letterpress blocks) is called Dry Offset printing. One can therefore call this Waterless Offset Printing (WOP). Unlike in letterpress the images will be in readable form as the images are printed through intermediately blankets. As the name implies dry offset, refers to the absence of dampening unit on the machine in contrast to wet offset lithography wherein water is used to dampen and repel oil-based ink from the non-print areas of a printing plate. Since the water ink balance has to be maintained in the Wet Offset, which if not properly handled cause much press related problems like plate blinding, scumming etc, Dry Offset presses print faster without much technical problems. It is also easier to make the plates for Dry Offset, is a high speed process with low cost. The additional advantages are changeovers of the jobs are easier and simpler.
15. Din sizes : When the saga of printing began paper manufacturers were able to produce paper in different sizes. Each country had their own sizes of paper. Some of the popular paper sizes in use included sizes like Demy(171/2’’x 22 1/2’’), Medium (18’’ x 23’’), Crown (15’’ x 20’’) , Imperial (22’’ x 30’’), Royal (20’’x 25’’) etc. This could not standardize the sizes of books and other printed material and lead to paper wastage besides under utilization of machineries and equipments. Therefore in order to standardize the paper, in the year 1920 German institute of standardization began standardization in general with the introduction of DIN sizes called Deutsche Industrie Normen . Later the term of DIN was replaced by International Organization for Standardization called ISO. The papers were manufactured based on the standardized sizes namely A, B & C, so as to have their subdivision fall in the same proportion.
The advantages of standardization are obvious for efficiency of paper production, printing equipment, print production, storage, easy calculation of weight or their conversions etc. There have been many standard sizes of paper at different times and in different countries, but today there are two widespread systems in use: the international standard sizes (A4 and its siblings) and the North American sizes. The international paper size standard, ISO is based on the DIN size only.
ISO paper sizes are all based on a single aspect ratio of square root of two . For example the Ao size of paper is defined to have one meter square. The subsequent sub divisions of the Ao sizes are A1, A2, A3, A4, A5 etc which are just half the size of the paper when cut into two on their longer side. The system allows scaling without compromising the aspect ratio from one size to another – as provided by office photocopiers, e.g. enlarging A4 to A3 or reducing A3 to A4 and so on. This being the ratio, the weight of each sheet is also easy to calculate for costing purposes.
A series are the most popular and most practical used for general book and all varieties of stationery printing. B series is intended for larger print work such as posters and Maps. The C series however are meant for the envelope sizes designed to compliment the A series sizes.
............Additions to alphabet D to be continued under D/3