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Jpeg and Tiff
Exporting bitmap pages :-

Creating your whole artwork as a bitmap file is usually not the best way to go. It can be done and sometimes it is the only way but in 99% of cases you will get better results if you use bitmaps only for holding photographic content and photographic effects that are then placed in a vector based program (Quark, Coreldraw, Freehand, etc.) to be combined with other page elements. This is mainly because bitmaps do not support advanced printing concepts that are essential to getting optimum results from
postscript based offset litho systems. Bitmaps don't understand trapping, overprint, scaleable type, optimised curve rendering, etc. For more professional results use your bitmaps to hold your pictures, clipping paths and photagraphic backgrounds but create your final artwork in a vector package.

What is a Bitmap
A bitmap is as its name suggests - a map of bits or pixels. If you look very closely at your computer monitor you can see that the image is made up of a big rectangular area of different coloured pixels. This is an example of an RGB bitmap. (RGB means that each pixel is made of a mixture of red, green and blue light) Each pixel on your monitor is defined by its position and its colour. A higher resolution monitor will require a bigger bitmap to define it eg 1024x768, 1280x1024, etc. Bitmaps readily lend themselves to computing and print applications because they can be saved to a file and transported around and read by many different programs and devices. A bitmap does not need to be RGB, in fact for printing applications RGB is meaningless since printers print using coloured inks not coloured light. Bitmap colour spaces used in print are :
CMYK (cyan,magenta,yellow,black inks ie colour pictures),
Greyscale (black ink only, uses dots to simulate a black and white photograph),
Monochrome (black ink only but no dots, no shades of grey).
In all cases white is produced by not printing anything ie blank paper.

How are Bitmap files produced?
Bitmaps are usually produced using some form of scanner or by using a bitmap editor program like Photoshop. Scanners normally produce an RGB file that is then converted to CYMK, Greyscale or Mono via software.

Mapping Colour Spaces
Everything you scan and everything you look at on your monitor starts life as an RGB image. Since we cannot print using RGB there must always be a conversion to a suitable format for print. The number of discrete colours that can be printed on a press is much less than the number of colours you can scan or view on your monitor. This can cause problems because an RGB monitor or scan colour often doesn't map directly to a corresponding CMYK print colour. In other words when converting from RGB to CMYK much of the colour information must be discarded in order to allow your image to fit into the smaller colour space. Much work has been done by people with big brains in creating colour tables and colour profiles to manage this conversion process whilst trying to maintain as much of the perceptual relationship between colours as possible. In other words when we print your colour pictures we will attempt to trick your eye into thinking the colours that have been discarded are still there. This is not always possible and a skilled designer will modify his artwork to compensate for these deficiencies in CMYK printing. If you do not convert your files to a suitable format we will do this for you using our standard colour tables and profiles. This conversion will be done as part of an automated process with no operator input (since you are not paying for operator involvement) and may not produce the results you want.

Increasing Bitmap Resolution
It is important that bitmaps are created at a suitable resolution (see below). This is because although you can easily increase the resolution of a bitmap, the bigger bitmap will contain only the original amount of image data. This means it will be at a higher resolution but it will not look any better. An image that is 72dpi at same size will still look 72dpi at same size even if you make it 9000dpi. You are effectively taking a high res photograph of a low res image and you will capture all of its imperfections in fine detail.

Bitmap Settings
You need to use the correct settings when creating your bitmaps.
Resolution : In all cases ideally never less than 300dpi at same size
CMYK or Greyscale Picture Resolution : Ideally 400dpi at same size
CMYK or Greyscale Lineart Resolution : Ideally 600 - 800dpi at same size
Monochrome Lineart Resolution : 1200 dpi at same size
Compression : JPEG at maximum quality or LZW
RGB Stuff: Convert to suitable colour model

REMEMBER : To add required bleeds and gutters. Convert everything to CMYK that should be CMYK and everything to greyscale that should be greyscale. Do not send RGB bitmaps unless you are happy to live with our automatic colour conversion.