When you are preparing images for printing you can take care of just about any situation with just two file formats.
Here’s why TIFF and EPS are the formats of choice for images for printing, and some tips for getting the best results with them.
1 TIFF – for tone images for printing
The TIFF format is the most reliable choice for handling continuous tone images, such as photographs. A common option available in TIFF images is LZW compression. This is a lossless technique, meaning that no image data is lost when an image is compressed. This is useful for working files and archiving purposes, but LZW compression can cause problems in some RIPs (the processor that converts your layout files to a form suitable for use on press) and is best disabled for final print files.
2 EPS – for vector artwork
The EPS format can handle vector artwork, which are images with shapes described mathematically, as well as tone images or combinations of the two. It also works reliably for more complex image structures incorporating separate plates such as duotones and spot color channels.
3 EPS gotchas
The EPS format can include type, process and spot color plates, and allows a lot of flexibility in placing other images within your EPS image. This means care is needed with the details.
- Fonts are not necessarily embedded in an EPS file, so you may need to package them separately for output, just as you would for a layout file.
- Spot colors must have exactly the same name in the EPS file and the document where the image is used, to avoid extra separation plates.
- If you place bitmap images in your EPS illustration, make sure to embed them or supply the files separately for output, or they may reproduce at low, preview resolution.
- Avoid placing another EPS illustration in your EPS file – it can crash the RIP. It is better practice to extract the elements from the second EPS file and place those directly.
- Custom screens, dots, angles and rulings are possible in EPS files, but can make an image reproduce poorly, or even cause the RIP to abort the job. They are best avoided.
4 Images for Printing – Formats to avoid
The JPEG format’s strongest feature also makes it less suitable for use in images for printing. It achieves very high file size compression by selectively discarding image information. This detail cannot be recovered, and the resulting image degradation is revealed by the high resolution of print reproduction. Similarly, GIF and PICT format images were not developed to handle the resolution and color spaces required for print.
- JPEGs can give good results as images for printing only if they have been saved at 100% file size, that is, without any compression.
- If you need to work with a JPEG file, save a copy as a TIFF as the first step. Resaving a jpeg degrades the image each time it is saved.
5 The color space race
RGB images look great on screen and on the web, but do not work in print – they are based on the color qualities of transmitted light, while CMYK and Pantone® spot colors are based on the properties of pigments that reflect light. Convert RGB images to the CMYK colorspace before placement in your layout application.
6 Scale, rotate, manipulate
Any scaling or rotation applied to an image in a layout program creates unnecessary processing overhead for the RIP and may cause output to fail. Instead, create a copy of your original image then size, rotate and manipulate it as needed within your image editing program, before placing it, as is, in the layout document.