Alternatives to Native Formats
You might also consider saving your Photoshop files as layered PDF or TIFF files. Most people don't realize that TIFF files can include layers and transparency, and that InDesign can read that information just as easily as if the image were a .PSD file. The reason is that layered TIFF files are a combination of a flattened TIFF and a layered .PSD file. Programs that can read the layered information (like InDesign), do so; programs that cannot (like XPress), read the flattened part. The problem is that layered TIFF files are even bigger than .PSD files. For that reason, many people prefer flattened TIFF files.In general, Photoshop PDF files are the most flexible format; they can be flattened or layered, include vector and transparency information, and are often surprisingly small on disk. Unfortunately, InDesign can't read spot colors inside Photoshop PDF files. (XPress 4 cannot read Photoshop PDF files at all, though XPress 5 can, with some limitations.)
Recommended Prepress Formats
As we said earlier, InDesign can accept almost any graphic file format you'd want (though it doesn't handle specialized 3-D file formats, Painter files, or CAD files). There's no problem with your using flattened TIFF, EPS, and JPG files rather than native file formats. Here are a few tips that might be useful:
- TIFF. This is normally the format we use for saving bitmapped images (if we're not using a native .PSD format). TIFF files can even contain alpha channels or clipping paths created in Photoshop.
- EPS. The Encapsulated PostScript (EPS) file format usually contains a low-resolution, low-quality PICT or TIFF preview which, by default, InDesign uses to display the image on screen (like QuarkXPress). However, unlike XPress, InDesign can also interpret the PostScript code in the EPS file and display a high-quality version on screen (see Chapter 66). InDesign can also produce its own proxy preview if one doesn't exist. When printing to a non-PostScript printer, InDesign rasterizes the PostScript so you get a high-quality print, much better than you'd get from XPress.
- JPEG (.JPG). The Joint Photographic Experts Group (JPEG) uses a "lossy" compression mechanism which can cause image quality to deteriorate significantly. InDesign can import and print JPEG files, but you should make sure you use a minimum of compression (maximum quality) or else you will likely see image degradation, especially artifacts appearing around sharp high-contrast edges. (Of course, if you're printing to newsprint, no one will notice.)
- PDF. As we noted above, PDF is a very flexible and robust file format. We now generally prefer this over the EPS format for vector artwork. However, note that when you make a PDF file, the default in every program we've seen (Distiller, Photoshop, and even InDesign) is to compress bitmapped image data with JPEG compression, degrading them in the process. If you want to save all your image data, turn off compression or use the ZIP setting instead of JPEG (ZIP is a "lossless" form of compression).
- DCS. Desktop Color Separations (DCS), developed by Quark, is a version of the standard EPS format. The only good reason to use DCS is when you have a Photoshop image with spot color channels. However, note that DCS files don't support transparencyyou can't even put something transparent over thembecause InDesign can't get at the high-resolution data (see Chapter 94).
Inappropriate File Formats
Just because InDesign can import and print some file formats doesn't mean you should run out and use them. Here's a list of file formats that InDesign supports, but which we recommend avoiding if you're doing prepress work: GIF, PNG, BMP, PICT, WMF, PCX, Scitex CT. (If you're doing multimedia work, exporting PDFs from InDesign for the Web, then some of these may be appropriate.)
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