Today’s Question: [As a follow-up to yesterday’s question about preparing images to be printed by a lab], all of the labs I have come across instruct us not to use the profile for anything other than soft proofing. Most of them seem to want the print file in sRGB. Can you clarify? Also, most of the labs seem to want JPEG images, which doesn’t seem to make any sense. Why would they prefer JPEG?
Tim’s Quick Answer: I have a feeling that the reason many print labs prefer a “generic” working space profile rather than a specific profile is because many photographers don’t convert the images properly, creating difficulty for the printer. And I suspect the request for JPEG images is because the print lab is prioritizing small files that can be transmitted online more easily over final print quality.
More Detail: A profile for the specific printer, ink, and paper combination being used to print an image defines the specific range of colors (the color gamut) for that print condition. As such, that profile is the optimal profile to use not only for soft proofing the image but also as the actual embedded profile saved with the image.
In other words, if the printer has an ICC profile for the intended output conditions, it is indeed best to convert photos to that profile before sending the file to the printer. If there is a chance that a different paper or set of inks will be used to print the image, then it could certainly be advantageous to keep the image in a working space profile rather than a specific printer profile. But in general the specific printer profile is the best option.
As noted above, however, I suspect part of the reason that many print labs instruct photographers to use a working space profile rather than a specific profile is that photographers might be less familiar with the use of custom profiles, leading to images that haven’t been prepared correctly and therefore might not print as well as they should.
As for the request for JPEG (rather than TIFF) images, I am sure this is simply a matter of wanting a smaller file that can be easily transmitted through an online service, via FTP, or possibly even via email. However, you are sacrificing a degree of print quality when a JPEG rather than TIFF image is used as the basis of a print.
To be sure, it is possible to produce very good prints from a JPEG image. In fact, many magazine covers are printed from a JPEG image. But there is a risk of visible compression artifacts in the final print if the source image is a JPEG rather than a TIFF (or some other format saved with lossless compression or no compression at all). When you save a JPEG image, even at the highest quality setting, there is always some degree of lossy compression applied, and therefore some risk of visible compression artifacts in the image.
The specific risk when printing from a JPEG image depends upon the content of the image, the size at which the image is printed, and the quality setting used for the JPEG image. However, my preference would be to avoid these risks altogether and save in a format (such as TIFF) without lossy compression being applied.