Delivering files for troublefree output (part 4)

Delivering files for output

File formats: Save your images in either TIFF or EPS. Avoid other formats like PICT, GIF or BMP.
Rotation: Try not to rotate line art images in a layout application if you still use a PostScript level 1 RIP. This can slow down the RIP a lot.
Resolution: Make sure images have the correct size and resolution while scanning them. The final resolution of bitmaps should be somewhere between 800 and 1200 dpi. So if you scan a logo and want to enlarge it 300 percent in the layout application, it should be scanned at 2400 to 3600 dpi. For output on digital presses, a resolution of 600 dpi is often sufficient.
Size: Never enlarge images more than 20 percent in your layout application. It will reduce the resolution of the images and lead to an effect called staircasing.

File format: Save your images as either TIFF or EPS files. Avoid other formats like PICT, GIF or BMP.
Highlight and shadow dots: The clearest point in grayscale images should not consist of pure white but should have at least a 2% dot in it. The darkest area of the images also shouldn't consist of pure black. For 133 or 150 line screens, it is customary to use a 95 percent gray for the shadow dots. For newspaper printing, a 5 percent highlight dot and 80 percent shadow dot is not uncommon.
QuarkXPress and TIFF: When placing TIFF images in QuarkXPress (Mac or PC) make sure to never have the background colour of the picture box set to "none". This avoids problems with staircasing (so-called jaggies) at the edges of the image.
Resolution: Make sure images have the correct size and resolution while scanning them. The final resolution of black and white pictures should be (screenruling x scale x 2). The "2" is a quality factor that can vary between 1.6 and 2.5 depending on your quality needs and the subject of the image. So if you scan a photograph and want to enlarge it 300 percent in the layout application and your publication is printed at 85 lpi, the image should be scanned at (85 x 3 x 2) or 510 dpi.
Size: Never enlarge images more than 20 percent in your layout application. It will reduce the resolution of the images and lead to an effect called staircasing. Reducing images too much will lead to a loss in sharpness and contrast.