Vector & Raster Images
Vector images are created by placing points on a grid and drawing lines between those points. A colour can then be added to “fill in” the lines that have been created. Vector images are resolution-independent. This format is best for logos or cartoon illustrations. Photos however will not appear true using this type of format.
Raster images use a Bitmap where each pixel is mapped with a colour. When increasing the size of a flattened Bitmapped image, the image will lose quality and appear “Pixelated”. However, photo’s will still appear true depending on the quality of the dots per inch (DPI) of the image.
Printers use CMYK (Cyan, Magenta, Yellow and Black) whereas on screen we use RGB (Red, Green, Blue). You need to ensure your document is set up in CMYK, otherwise, your print could come back not how you expected. When you convert your image from RGB to CMYK, it may appear duller, you may have to brighten up the colours to compensate.
Convert fonts to outlines
It’s important that when you send a document to print you convert the fonts to outlines. This basically means that rather than the type being an editable font, you change it into a shape layer. This will stop any font issues occurring at the printer’s side. In Adobe Illustrator it’s as simple as selecting all your type and then clicking Type > Create Outlines
On screen we view images at around 72dpi; however, printing requires a much larger resolution, usually about 300dpi. This means you can’t use low-resolution images as they will appear pixelated; you will need a larger image file. You can check the image resolution in Photoshop by selecting Image>Image Size.
Supply your file as a PDF
You can create a PDF file from most programs now, and it’s the easiest file for the printers to use. When saving your PDF you can select to include crop marks and a bleed; you can also ensure the resolution you want to save the file at. Supply PDF as separate pages not spreads. You can also run a pre-flight check in Adobe Acrobat, and you can set it up to check for various things such as image resolution, bleeds, spot colours etc. This is really helpful to check that you haven’t missed anything.