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Brian Lawler

Ansel would not approve
October 19, 2007

I don’t know what Adobe is thinking! When making PDF files from InDesign or Distiller, choosing:

High-Quality Printing
Press Quality
PDF/X-1a
PDF/X-3

all result in JPEG compression of very high-resolution images. In the world of really high-quality printing, I don’t want anyone to apply JPEG to any image – ever!

The fact that the Adobe high-quality settings all apply JPEG to high-resolution images just astonishes me. This compression only applies to images with resolutions greater than 450 ppi, but the highest quality printing jobs such resolutions are not just in the realm of possibility, they are quite likely. When building documents in InDesign, I often ignore the resolution of my very-high resolution images, as the resolution is irrelevant to me when printing to aluminum plates for offset printing. But, I don not want to do harm to the images by applying JPEG compression to them.

What’s another dozen megabytes of information in images when printing to the highest quality standards? And, more importantly, why would anyone with an interest in the highest quality images ever apply JPEG harm to their images?

Adobe’s PDF settings can be modified so that high-quality images are not subjected to JPEG harm.

The solution is easy, but not obvious. Anyone making a PDF with high-quality images they want left alone should make custom PDF settings to subvert the “automatic” JPEG compression that takes place in all of the so-called high-quality PDF settings from Adobe. You can simply choose “Do Not Downsample” in the menu from which these settings are made. Be sure to do this for both color and grayscale image settings.

Once these changes have been made, save the PDF settings as your own, and use the settings whenever preparing PDF files for print at the highest quality.

Posted by Brian Lawler on October 19, 2007 | Comments (3)

Industries: New Products, Premedia, Press

October 22, 2007
In response to: Ansel would not approve
Jim Webber commented:

Careful, Brian. It appears that you're mixing up downsampling with JPEG compression. For very high quality reproduction (as in 10 micron stochastic or very high screen rulings) you wouldn't want to use these settings, but for the vast majority of commercial printing (as in publications work) anything more than 300 dpi is wasted data that has to be transferred and Ripped. There is a real value in downsampling. JPEG compression is another story. First of all, it is applied to ALL image files in these PDF settings, not just high (over 450 dpi) resolution ones. Secondly, by default the JPEG compression settings are for maximum image quality. There are studies out there which document the effect of different levels of JPEG compression, including the new JPEG2000 standard. I would suggest you provide some information on those.

October 22, 2007
In response to: Ansel would not approve
John Clifford commented:

Hmmm, While I thoroughly agree that you shouldn't have COMPRESSION, I'm not sure that I agree that you shouldn't DOWNSAMPLE. I sometimes overscan images so that I have a little more latitude in scaling within InDesign, then let ID downsample to the 300dpi for my printer. However, I ALWAYS turn off compression in the drop-down menu just below the one shown in your article, which gives me the option of jpeg (VERY BAD), ZIP (OK, but doesn't do much compression for images, or NONE, which is my preferred compression. Jpeg COULD be used if you're sure to set the quality to Maximum (two drop down menus below the one in your screen capture). I was involved in some tests that showed that "visual" artifacts don't usually show up until an image has been opened and resaved about 10 times at this setting. However, no jpeg is still better!!! I teach prepress at Fashion Institute of Design and Merchandising in Los Angeles, and have a hard time convincing my second year design students to stop using jpeg. But I stubbornly try!

October 25, 2007
In response to: Ansel would not approve
Brian Lawler commented:

Yes, right on both counts. I recommend NEVER using JPEG compression in a quality print work flow. The downsampling issue is another topic (which I will take up in tonight's blog). Some people argue that downsampling is acceptable, others say it causes (sometimes) visible harm. I am of the opinion that you should leave the images alone. I also acknowledge that the RIP will have to work harder to create the halftone data for very-high resolution images, but my experience with modern RIPs is that the time spent on these images is negligible. I remember a time when that time was not a trivial matter, and I spent hours preparing my files for the RIP so that no extra data were sent to the RIP because it cost me money to do so.