Compressing Photo Files

For the past twenty years I have been a member of a freelance group that includes writers, editors, and designers. It’s an ideal place to be, since I have been all of these and since I now am a printing broker. I learn a lot from the other members (primarily online these days, although we used to meet in person).

One of the members of this group has a client in Afghanistan. The client has very slow Internet access, so reducing the size of files this particular designer sends to his client is of paramount importance. As nice as a design might be, the client still has to be able to download and review the art files.

So this designer opened up the discussion to the online group, asking how he could make a rather photo-heavy PDF of his book smaller. These were some of the approaches discussed in the online forum:

1. First of all, the rule of thumb is that at the final printed size, the resolution of a photo needs to be twice its line screen. That is, a 4” x 6” photo that will be printed using a 150-line halftone screen (the printer can tell you the line screen if you ask) should be 300 dpi in resolution at the final printed size. This will take up a certain amount of disk space as a Photoshop TIFF file (a format I and most other designers use for photos), and when you’re building an InDesign document of book length, the size (in terms of megabytes of disk space) of the InDesign file with photos will be very large. It will still be large even when distilled into a print-ready PDF. As a work-around, one of the freelance group members suggested reducing the resolution of the photos from 300 dpi to 240 dpi. This, he noted, would reduce the file size of the images and hence the overall size of the InDesign document and the resulting PDF file. The freelance designer also noted that there would be no discernible difference in the output quality. The key word here is “discernible.” The eye can’t see the difference in resolution.

2. The same designer also suggested the following. If you select the background areas in a photo and apply a very light Gaussian blur, the JPEG algorithm will compress the slightly blurred background areas more than the foreground areas, resulting in smaller photos with no discernible loss of quality. In essence, this is also a way to trick the viewer’s eye. The background areas of a photo are less of a focal point for the eye. The eye looks primarily at the subject matter and does not register the slight blur in the background.

3. Since I personally avoid JPEGs and instead use TIFFs, I suggested to the group that using LZW compression to make the individual images smaller in size would be a good option. JPEG is a compression algorithm, so it makes saved photos smaller (fewer megabytes in size), but it also does this by discarding image data. Plus, if you reopen the file, make more changes, and then resave the photo, you further degrade the image. This may or may not be visible. So, instead, I use LZW compression, which is “lossless” (i.e., no loss of image data), as opposed to JPEG, which is “lossy.” But I still benefit from the compression. The compression makes the individual image files smaller, so the resulting InDesign file (or PDF) is smaller and therefore easier to send over the Internet.

4. Another designer suggested using a cloud application like Box. You can upload your file to an online server and then just send your client a link to this online drive. Your client can then download the file from this server. I personally use this option when I want to send a large PDF to a client but can’t because it’s too large to just attach to an email. Based on your usage, I believe this is free. At least I’ve never used it enough to be charged, although I’m sure full-time designers might exceed the limits for free use and incur a fee.

5. Another designer on the freelance forum suggested using a lower overall resolution for the PDF file sent to the remote location. More specifically, you can save an InDesign file as a PDF using a number of presets, ranging from “smallest file size” to “high quality print.” If all your client needs to do is see a visible but lower-resolution version of the photos in a multi-image print book file, saving and then sending a lower-resolution version of the file may be an option.

6. Still another designer reminded us that when you reduce the size of a photo in InDesign, or even just place it in an image box (picture frame) that crops or tilts the photo, you’re adding unnecessary size to the overall InDesign file and therefore to the resulting PDF file. So, more specifically, the best thing you can do is crop, size, and tilt (if you’re tilting the image) the photo in Photoshop and then import it into the InDesign image box at the proper size and orientation. This will make the overall InDesign file smaller than doing all this work in the InDesign file itself.

Keeping all of these workarounds in mind, I still think the most prudent approach is to consider the use of the file you’re sending. If your client has spotty Internet capabilities (albeit a rare occurrence now), does she/he really need to see the highest resolution file and images just for editing purposes? If not, create a small PDF optimized for screen viewing and then wait to send the offset or digital printer the final high-resolution art files. He will most certainly have the most up-to-date Internet connection and ability to receive large native InDesign files and high-quality, press-ready PDFs.

Xerox’s Iridesse Press and Specialty Inks

I recently read an article entitled “Xerox’s New Iridesse Press Creates Unique Club Passes for Festival” by David Savastano, the editor of www.inkworldmagazine.com. It was published on 7/3/18.

What interested me about this article is the growing use of digital inks not for aesthetic purposes but for functional ones, such as security.

Just as paper money now includes holograms and strips of various kinds, small type, and a host of other devices to keep people from forging the dollar bills, Savastano’s article notes the specific ways Xerox’s Iridesse press personalized passes for the Xerox Rochester International Jazz Festival.

Savastano notes that in addition to printing the name and photo of each attendee, the Iridesse press used metallic and clear digital ink to produce “infrared print and microtext imaging” (“Xerox’s New Iridesse Press Creates Unique Club Passes for Festival”). That is, the variable text (a benefit of using digital printing) cannot be read under ordinary light but can be read under infrared light. In addition, the Xerox Iridesse can print text that is 1/100th of an inch in height (using the MicroText Specialty Imaging Font). This text can only be read under a magnifying glass.

The benefit of all of this is that only people who paid for this particular jazz festival could attend because forging tickets was not a viable option.

What makes this interesting to me is that all of this is an infinitely variable process, and the metallic gold or silver dry ink, CMYK ink, and clear ink can all be applied in a single pass to make documents of any kind safe from forgery in a quick, infinitely variable, inexpensive manner.

[Steven Waxman is a printing consultant. He teaches corporations how to save money buying printing, brokers printing services, and teaches prepress techniques. Steven has been in the printing industry for thirty-three years working as a writer, editor, print buyer, photographer, graphic designer, art director, and production manager.]