Scanning for DTP - Image Formats Tutorial

Scanning for DTP - Image Formats
Submitted By: GTS Learning
Published Date: 24th May 2001
Viewed: 25,412 times


This tutorial is a sample chapter from a course within the Beginners.co.uk membership area. To view the full course and hundreds of others, click here. An annual training membership costs only £99 OR $149 which gives you access to over 400 full courses.

This tutorial goes through the different formats of images that can be used when scanning images.

GIF Images The .GIF format was devised for the American bulletin board service CompuServe, as a compact format for sending image files via modem. There is also an interlaced version which comes up on screen in alternate horizontal lines, to give the recipient at one end of a modem link an idea of what the image looks like before the transfer is completed, so he can cancel the transfer if he prefers. Colour photos are often stored in .GIF format, and many bitmap-editor programs can read and write .GIF format. GIF is the format of choice in which to save flat-colour images that are to be included in a World Wide Web page on the Internet. GIF's biggest drawback for DTP use is that it can only store a maximum of 256 different colours per image. For photographs or images that contain a lot of detail the JPEG format is a better choice for web graphics. TGA Images TGA (or Targa) file format is for 24-bit colour images, and is commonly used in conjunction with 16-million colour graphics display cards and video capture boards. It is supported by bitmap editing programs, but not usually by DTP packages, for which conversion to TIF or PCX will be necessary. Photo-CD In Kodak's Photo-CD system, you can hand in your 35mm slides or negatives to a high-street photo lab, who will send them to Kodak where they will be scanned and recorded on a gold CD-ROM disk which can be read by most modern computer CD-ROM drives. The service takes about a week, and the transfer to CD-ROM costs around £5 for the disk and 60p per image, with a minimum order of 10 images. Ordinary developing and processing is additional to this. Standard Photo-CDs can hold up to 100 pictures, and the disk can be sent back several times to have more images added until its full capacity is reached. Photo-CD was designed as a domestic format (to allow users to view their pictures via an ordinary television linked to a special CD player, but it has caught on with DTP users to a much greater extent than with the general public. The normal Photo-CD disks can accept 35mm images only, but a professional version (Pro Photo-CD) has recently been introduced which will allow medium-format (5x4, 6x6, and so on) frames to be scanned and recorded. Pro Photo-CD is sold through professional photo labs rather than through high street outlets, and a fast (often same-day) turnaround is offered. Photo-CD is a convenient format for the storage of raw images before editing, as they can be left on the CD-ROM until required, thus freeing hard disk space. The image can be extracted from the .PCD file in a variety of different resolutions, according to the quality needed for the job. An advantage of using Photo-CD is that the actual scanning will be done on a high-quality drum scanner by experienced technicians, and at moderate cost. However, images will not necessarily get individual attention on the standard service; you will generally have to adjust the colour balance and contrast before placing the image in a DTP application. To use Photo-CD on your computer you need a CD-ROM drive which is multi-session; that is, it can read data that has been recorded on to the disk on more than one occasion. Almost all drives now are compatible, but check if you are offered a very cheap drive or buy one second-hand; it may not be suitable. It is best to get a six-speed (or faster) drive as this can be used for multimedia as well, and these are now the norm. If you plan to use Pro Photo-CD or image library disks containing high resolution images, you should look at the eight- and ten-speed drives which are now on sale, albeit at a price premium. CD-ROM drives can usually be networked so that several people can use them, and carousel models which hold several disks are available specifically for this purpose, notably from Pioneer. EPS Images It is possible to save bitmaps in EPS (Encapsulated PostScript) format. However, the resulting file can only be printed on a PostScript device, and sometimes cannot be reopened for editing. This format is best used as a last resort when transferring files from one computer to another, if there is no other common format that can be used, or if the image needs to be masked (qv). The one situation in which .EPS images are useful in bitmap editing is that you can import a drawing from a vector graphics package such as Corel Draw or Adobe Illustrator to use as a mask or ready-made outline. Check the manual for your particular program to see if it can do this. Note that the drawing must be saved specifically in Adobe Illustrator format (.AI/.EPS), not generic PostScript. Native Formats Some photo-editing programs also have their own proprietary file format (such as Adobe Photoshop's .PSD) which retains all image data without compromise but is often unreadable by any other application. Use native formats for saving work-in-progress, then save the finished product in one of the more general file formats (such as TIFF or JPEG). Native formats support special features of the software (such as separate layers, selection masks, and printer setup information within the image) which often cannot be saved with generic file formats. Note: In the PC environment it is a good idea to get into the habit of using the appropriate file extension when saving scanned images, as many software packages rely on its presence to auto-detect the relevant file format when loading an image for editing. Macintosh software can usually detect file formats without the extension being present.

Previous Page