Custom Printing: Finding Flaws in a Lenticular Book

My fiancee recently bought two copies online of the same lenticular book as gifts from two separate vendors. When she had both in hand, she was surprised to see differences between the two. Naturally enough, when she had bought the books, since they were two copies of the same title, she expected them to be the same. So she brought this to my attention and asked me what had happened.

First of all, I refreshed my memory online regarding the lenticular custom printing process. Many if not most of you have seen the images that change as you tilt them from side to side. These plastic screens are sometimes used in postcards, for instance, to give a sense of movement to an image or to shift from one image to another. I have also seen lenticular movie posters that give the illusion of depth in the photo by using this technology.

The short description of what seems to be a very complicated process is that a number of images (or one image seen from a number of different angles) are combined (interlaced) with a computer, then printed, and then attached under a screen composed of lenses (lenticules) that present a different image as you tilt these plastic screens. Alignment is crucial for this to work successfully.

How the Two Books Differ

What I see most prominently when I look at both books under a good light is that one set of lenticular images is more intensely colored than the other and the contours of the animals in the images (each page spread presents a different image of a wild animal running) are crisper and more defined. I don’t think the average viewer would see the problem unless both books were viewed together under a strong light. Personally I think it is rather intriguing.

In my research I found that ghosting and poor imagery are the result of imprecise alignment of the images that have been transformed from individual photos to interlaced “slices” before being placed under the cover sheet of plastic lenses. This can occur during the printing process, which, for this particular technology, would be either screen printing or offset lithography.

Other Color Flaws in Other Kinds of Commercial Printing

As I compared the two books I was reminded of package printing I had seen in grocery stores, in which the images in two cereal boxes, for instance, might be slightly different in color even if the design clearly should have been the same (both content and coloration). How does this happen?

First of all, it doesn’t happen anywhere near as often as it used to even during my own career in commercial printing. You could say that the two packages with slightly different ink coloration had been from two separate press runs, and this might be correct. However, it would not really answer the question as to what had happened.

On an offset printed package, for instance, one particular ink color might have been run in excess. Another possibility is that the four process color plates for a full-color image might have been out of alignment (out of register). An error in “registration” of the custom printing plates could cause an obvious color shift, particularly in a neutral color or a memory color (like the green of grass or the blue of the sky).

However, this doesn’t happen a lot anymore for two reasons:

1. 1. A large number of offset presses are equipped with closed loop color monitoring. Optics and electronics on the press closely monitor the registration of all printing plates and the particular colors being printed and then feed this data back to the press console, adjusting the press and ink to maintain good plate register and consistent inkflow at a predetermined level. When the automatic press observations record an error, the press is adjusted to bring everything back into equilibrium, correcting the color problems and problems with image register.

1. The preset ink levels can be captured as digital data, which can then be fed back into the computer for the second press run. This actually allows the press to “come up to color” or achieve the optimal color balance rather quickly, meaning that usable printed sheets start to come off the press with minimal adjustments and minimal paper waste. Because of this, it is unusual to have errors in color between two different press runs yielding two differently inked product packages in your grocery store.

Back when I was an art director, the way to avoid these problems was to attend a press inspection for every press run of every signature in every critical product. These often went around the clock (every four hours, for instance) for a number of days. The aforementioned automation and the quality of inspection that electric eyes and computers can provide have made this unnecessary in most cases.

Another Possibility

One thing that I have found over the years is that not all commercial printing processes are equally precise. For instance, offset lithography can be surprisingly accurate. Given the size of the presses and the speed at which they run, I still find it amazing that they can produce tight register and incredible detail.

In contrast, the output I have seen from flexographic presses often does not quite match that of offset lithography. Flexography uses rubber relief plates (elements that print are raised on the rubber plates). I have often seen less precise register and in some cases lighter ink films around the perimeter of letterforms in large type. Like other aspects of commercial printing, it is my understanding that technology has been making great strides, and the problems are becoming far more rare in flexography as well. But my point is that some commercial printing technologies are more precise than others, and this can be reflected in the final product. And for packaging, the final product is often produced through flexography.

What You Can Do

Ultimately all of this comes down to one question. If commercial printing processes are imperfect, how can you be sure your job will be beautiful?

Here are some thoughts:

1. 1. Proof early and often. Make sure that you see “contract quality” proofs that your printer assures you will reflect the final printed product.

1. 1. In all cases, ask for your printer’s advice as to the most color faithful proofing option. Usually that will be some form of digital proof. Your printer may be able to show you a continuous tone proof or a proof reflecting the actual halftone dot structure. The latter is more rare but also more accurate (for instance, it will show potential moire patterns). This kind of proof is also more expensive.

1. 1. If you are unsure, consider paying more for a press proof (a proof of the final product produced on a small press). This will be expensive. However, for a job with crucial color requirements, it may be worth the cost.

1. 1. Consider attending a press inspection. While this is usually unnecessary, for “critical color” (as opposed to “pleasing color”) it may be worth your time.

1. Expect excellence, not perfection. You will always find flaws in printing. More than anything, it is a question of fixing the major flaws and letting the others go.

This entry was posted on Tuesday, May 30th, 2017 at 7:25 pm and is filed under Book Printing. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.