Pixel image file formats
Generally, all pixel based images should be saved as Photoshop (.psd) and Tiff (.tif) files as these are the most open format to use for our workflow.
There are times when other files may be more appropriate. Below is a list of some of their advantages and disadvantages to illustrate when and why they might be used.
Avoid using EPS (.eps) files on new projects as our workflow tools and checking systems cannot ready these formats, for backlist title reprints leave the file format as is unless there is a small amount to convert.
.psd
Good:
- Totally compatible with Adobe applications
- Based on latest technology
- Smaller files than .tif (if using layers, transparency, etc).
When to use:
- Use wherever possible when working with bitmap (photographic) images.
.jpg
Good:
- Small file size.
- Common format
Bad:
- ‘Lossy’ compression (ie: it throws away information in order to compress the file, so quality suffers).
- Every time you re-save a JPEG, you lose more quality (like making a copy of a photocopy).
When to use:
- OK for image libraries to use when first supplying files as long as they use the highest quality setting.
Don’t use:
- When re-saving files, as you will reduce the image’s quality each time you re-save it.
- But – OK to use if you are supplying low-resolution images to Sales which need to be small enough to email.
.tif
Good:
- Sometimes works in situations where .psd doesn’t.
- More universal format than .psd.
Bad:
- Need to manually tell it what information you want it to save (i.e.: alpha channels, transparency) which can cause confusion.
When to use:
- Use if .psd doesn’t work when you need to colour a greyscale image in InDesign.
- Use a ‘BITMAP TIFF’ when saving a scanned signiture. Go IMAGE > MODE > BITMAP. Input and output resolutions should be the same, make the resolution 1200dpi. Click OK. Save the file as a TIFF file format.
Don’t use:
- Usually: don’t use in preference to .psd.
.eps
Good:
- Can save Illustrator or Photoshop files as .eps
- Works with QuarkXPress 4 (which is still occasionally used for old books).
Bad:
- Based on old technology (PostScript), while Creative Suite now uses PDF as its core technology.
- Produces low quality previews when placing into InDesign document.
Don’t use:
- All old DK images used to be saved as .eps, but it should be avoided now, in order to avoid potential problems (either in-house or at the printer).
- Images from old books will often be in .eps format, but should usually be re-saved as .psd or .ai if they are being re-used.
Good:
- It’s a common file format that most people can open.
Bad:
- When used as an image format, it is only really functioning as a ‘wrapper’ for another file type.
Don’t use:
- Don’t use as an image format for files you intend to print from. PDF is great as a container for collections of information (text, images, page layouts, etc), but if you are just saving a single image, it is usually best to choose another format.
.gif
Good:
- Widespread usage on the World Wide Web due to its wide support and portability.
- GIF images can contain multiple frames and therefore can be used to create animations.
Bad:
- Limited to a maximum of 256 colours and therefore unsuitable for reproducing color photographs.
Don’t use:
- Don’t use as an image format for print files. The GIF format is intended for use with websites and other digital applications.
.png
Good:
- Designed to be an open-source successor to the GIF format.
- Can contain the same range of colours as PSD, TIFF, JPEG etc.
Bad:
- Can not embed colour profiles necessary to maintain our colour standards in print.
Don’t use:
- Don’t use as an image format for print files. The PNG format is best used within websites and other digital applications.