If you are scanning the photographs yourself, save them as either EPS or TIFF file formats as this will preserve the colour and clarity of your images. If you are scanning a printed item such as a magazine photo, you will need to ‘de-screen’ the image, blurring it slightly to avoid a moiré effect (see your scanning software manual for more details). GIF and JPEG file formats compress the image and actually discard certain information, causing colour
shifts and blurriness. You should try to avoid using either of these file formats. Unless you really do not have a choice, then you should save them(JPEG & GIF formats) in the highest quality setting. When you are scanning, consider the final size your image will be used at. You should at least scan photographs at 300dpi or at the appropriate size you are going to use them. There’s no point scanning a postage stamp at 300dpi and then blowing it up to a A4 size – use your scanning software to help you
calculate the output resolution.
Conversely, scanning photographs at more than 300dpi will have little or no effect on the actual printed quality and will unnecessarily increase file size and processing time. Don’t enlarge or reduce your scanned images in your drawing/vector software (such as Adobe Illustrator) It’s always best to use an image-editing application such as Adobe Photoshop for this task. When converting photographs from RGB to CMYK, refer to the settings on the left (from Photoshop
CS). In the ‘Edit’ menu choose ‘colour settings...’. From the window that appears, choose ‘custom CMYK’ from the list in the ‘CMYK’ section of ‘working spaces’.
Scan black and white line art (i.e. a logo), at 1200dpi for best results. Any lower, and the logo may look blurry. Pay careful attention to the CMYK makeup of any ‘black’ in your logo. The automatically-created Photoshop black, for example, provides 250% ink coverage. You may need to adjust the colour settings in your application to get a black that is made from 100% black ink. Make sure that any alpha channels are removed and all layers are flattened before finally saving
your image. You shouldn’t compress your image either, or it will cause problems. So LZW, JPEG and ASCII encoding are all not recommended. Don’t use DCS files, LAB colour, Duo-tones or Tri-tones either. Rather, you should convert them all to CMYK. Images to be used on the black & white reverse of a job should be saved as greyscale.