Image file formats to use in print pdfs

Question

We receive images from several vendors in order to build our catalogs in Adobe InDesign CS2, and then we export print pdfs from InDesign. We want to standardize our requirements for receiving images from vendors, and we had a question related to file formats. Is it okay to use jpeg files as long as they are in high-resolution CMYK format?
It is a part of our work flow to accept the images untouched from the vendor, no re naming of files, or changing f file formats. I understand that the safest bet is for EPS and TIFF formatted images, but will JPEG files be problematic in any way? Someone told me that because of their compressed format that some info could get lost when embedding into pdfs. Is there a book, or any printed documentation about what types of image file formats to use to create pdfs?
Thanks,
Elliott

Answer 1

(1) There is nothing "unsafe" about JPEG-compressed images. However, JPEG compression is
lossy and depending upon the type of image, its resolution, and the compression settings used when creating the JPEG file, the results at the end of the workflow may not be satisfactory. That having been said, if JPEG compression is used for a photographic image (not a screen shot or an image representation of what should be a vector diagram), the "maximum quality" setting is used in producing the JPEG image (
not maximum compression), and the image is of appropriate resolution for its final purpose (at least 150 dpi, preferably closer to 300 dpi for printing) at full magnification, then there is nothing "unsafe" about JPEG.
(2) You should be aware that saving images in EPS (Encapsulated PostScript) format from Photoshop may yield JPEG compression, depending upon options chosen. Thus, there is nothing inherently "safer" about EPS compared to JPEG. And ironically, you can also get JPEG compression in TIFF files if you aren't careful how you save them, although that is very uncommon.
(3) CMYK is not necessary for image placement into InDesign as long as the image is tagged with the appropriate ICC color profile (such as sRGB, Adobe RGB, etc.). InDesign can convert those RGB images to whatever the final print conditions are or, if creating PDF, leave the images in RGB format with the ICC profile. How you create the output obviously depends heavily on what type of workflow your print service provider has. More "up to date" printers support color-managed workflows with ICC color profile tagged images in PDF files.
(4) In terms of receiving images from vendors, if you require them to convert the images from whatever their native RGB color space is to CMYK, you really must specify
which CMYK and provide the correct ICC color profile to them! Different print processes use different CMYK color spaces. If you convert RGB to the wrong color space, the results can be awful. You are probably best off requiring that vendors submit photos in their original RGB color space, but tagged with the appropriate ICC color profile.
- Dov