Scanning tips

Scanning is the process of converting paper-based art (analog) to computer-based art (digital). Scanning is performed with the software that comes with your scanner. After the scan is performed the results often need to be cleaned up in a pixel-based software application like Adobe Photoshop. If you do not have this software, or are not experienced in manipulation images, K International's design studio can do this for you.

Scanning Photos and Illustrations

Scanning your photographs and illustrations with the proper scan resolution will enhance the output. Your scanning software will allow you to choose the resolution, which is usually measured in dpi (dots per inch).

Scanning at a resolution that is too high will slow the production process; whereas if it is too low, it will give printed photos a jagged appearance.

Use 226 dpi to scan photos that will come out at the same size as the original (e.g. if your original photograph is 4'' wide, and will be 4'' wide in the final output).

Use the following chart to determine your scan resolution for photos that will be reduced or enlarged.

DPI – what does it mean?

Resolution, scanning, and size of graphics can be a confusing topic. Before you panic, here are a few basic, easy to understand facts.

Resolution refers to the dots of ink or electronic pixels that make up a picture on paper or on a screen. DPI (dots per inch) is a measure of resolution, and is probably a familiar term if you use a printer, scanner, or digital camera.

• A picture (whether on paper or a computer screen) is made up of tiny coloured or black dots.
• In black and white printing, the size, shape and distance apart of the black dots creates the illusion of shades of grey.
• The more dots that are used (up to a point), the clearer the picture - and the larger the size of the graphic file.
• Resolution is measured by the number of dots in a horizontal or vertical inch, hence DPI (Dots Per Inch).
• Each device (scanner, digital camera, printer, computer monitor) has a maximum number of dots it can process and display, no matter how many dots are in the picture.

A 600 DPI laser printer can print up to 600 dots of picture information per inch, whereas a computer monitor can usually only display 96 (Windows) or 72 (Mac) dots per inch.

If a picture has more dots than the display device can support, the extra dots are wasted: they increase the file size, but don't improve the printing or display of the picture. For example, a photo scanned at both 300 DPI and at 600 DPI will look exactly the same when printed on a 300 DPI laser printer, but the 600 DPI picture will have a larger file size.

If there are fewer dots than the display device can support, the picture may not be very sharp. For example, pictures on the Web are usually 96 or 72 DPI, in line with the resolution of most monitors. If you print a 72 DPI picture on a 600 DPI printer, it won't look as clear as it does on-screen, as the printer doesn't have enough dots of information to create a sharp image.

Scanning Printed Photographs

When photos are printed, in magazines for example, the output device applies what is known as a halftone screen. A halftone screen allows a printer with one colour ink or toner, black for example, to achieve many shades of black.

Scanning a photo with a halftone screen will cause an undesirable effect when it is output – a moiré pattern. To avoid this hashmark-type effect, always scan in original, unscreen photographs. If there is no way to avoid scanning printed photographs, apply a blur to the scan until the halftone screen disappears. This may seem counter-intuitive, however it is important to blur away the halftone screen before it is output.

Scanning Illustration or Vector Art

If you are scanning a simple line art drawing, in one colour, use the ‘Line Art’ setting on your scanning options. This will give you sharp lines (they may not look particually sharp on screen, but will give a crisp image when printed) and the ability to change the colour of the drawing. For more complex illustrations, use the same method of scanning printed photographs.

Saving Scans

The most reliable file formats for scans are EPS and TIFF. When unsure, use the EPS file format. Make sure you set your EPS option to leave the ‘Halftone Screen’ box unchecked. This should be the default setting.

The TIFF format yields a smaller file, but can be more prone to data corruption. If you do choose to use the TIFF file format, make sure the ‘LZW Compression’ option is turned off.