Saturday, July 30, 2011

What the press operator is scrutinizing

It's the stereotypical image of a press operator - bent over the presswork and examining it under a loupe. People attending a press approval often wonder what the press operator is examining so closely. In fact there's a great deal of information that the press operator can determine from a close up view of the press work.

The first thing that's checked is registration.
On the left, dot centered rosettes indicate that the presswork is out of register by one half row of dots. On the right, clear centered rosettes shows the presswork is in register.

Misregistration can also be determined by examining the edge of images to see if one of the process colors is extending beyond the image edge. Click on the above image to enlarge.

Next is halftone dot formation.
Halftone dots can reveal issues such as dot doubling that may be the result of loose or incorrect blanket packing.

Here speckles of ink indicate there may be a problem with the plate processor. Also, in this case, the black printer is, because of the elongation of the dots, showing a problem with slurring.

The amount and type of halftone dot distortion can reveal problems with ink water balance as well as the condition of the fountain solution.

When halftone dots are the same size and should be the same approximate density as in the case of Cyan and Magenta - but aren't - this can signal a problem with the solid ink density or an ink/water imbalance.

Pinholes forming inside halftone dots can signal a calcium carbonate issue.

Tuesday, July 26, 2011

Things that make me go Grrrrrrrrrrr...

Pretzel hotdog buns, yum yum.
The package label says it contains 6 buns. I wonder what the ingredients are for just one bun?
Doh! Ingredients are listed by serving weight.
But what's a serving? Do I have to weigh the package to find out what makes up 50 g?

Why couldn't they have listed it as: "Per serving (one bun: 50 g)"?

Monday, July 11, 2011

Technical tips for creating brand colors

Color is one of the most critical components in creating brand identity and while there is a fair amount of information on the psychological and cultural aspects of color - there's very little information on the technical issues that need to be considered when developing a custom or brand color.

Brand colors are custom (a.k.a. line, spot) colors that are any single color (typically other than cyan, magenta, yellow, or black) that are usually printed as a solid area of ink on a dedicated press unit.

There are two types of custom colors -
1 Proprietary
2 Referenced.

Proprietary custom colors are colors that are created by the brand owner or their creatives. Coca-Cola red and Kodak yellow are examples of proprietary brand colors.
Referenced custom colors are usually published in color palettes that are to be used by creatives to specify spot colors.

The main brands of referenced custom color palettes are:

Pantone, the dominant spot color printing system in the United States and Europe.
Toyo, a custom spot color system that is popular in Japan.DIC, Dainippon Ink & Chemicals, Inc., another popular Japanese custom color system.
ANPA a palette of 300 colors specified by the American Newspaper Publishers Association for spot color usage in newspapers.
HKS Hostmann-Steinberg Druckfarben, Kast + Ehinger Druckfarben und H. Schmincke & Co. a custom color system containing 120 spot colors and 3250 tones for coated and uncoated paper.
The main benefit of creating a proprietary brand color is that it is unique to the brand thereby enhancing the brand's unique identity. The downside is that the creatives/brand owner are required to create their own system of specifying, communicating, and manufacturing the color.

The main benefit of using colors from a reference custom color palette is that the system of specifying, communicating, and manufacturing the color has already been built. The downside is that the color is not unique to the brand and can be used by others, potentially creating confusion in the marketplace.

When creating a new proprietary custom colors to be used for brand identity keep these technical tips in mind:

1- Humans have very good color discrimination for greens and much less for blues, reds, yellows, and purples.This means that they can more easily distinguish between subtle differences in two similar greens than they can two similar reds. It also means that there are more green custom color options than there are red.

2- In offset lithography, the range of possible greens is larger than that of reds, blues, and oranges

3- Humans have poor color discrimination when hues are very saturated - I.e. saturated colors will tolerate greater variation in reproduction before a color shift is noticed.

4- RGB, CMYK, and Hexadecimal values do not actually define colors because those values are device dependent. I.e. it does not, for example, tell us the specific hue of the Cyan ink being used - a factor that will change depending on the ink manufacturer.
A demonstration by Flint ink of the influence on ink color resulting from differences in the substrate upon which the ink is printed.

So, a color defined using CMYK values will also look like a different color when printed on newsprint, in a magazine, or in a brochure due to the differences in the specific CMYK inks used and the substrates they are printed on.
Instead, define the color using CIEL*a*b* reference values since these are device independent. If RGB and/or CMYK values must be provided then make sure that the version or source is included (e.g. sRGB, Adobe 1998 RGB, CMYK/SWOP, CMYK GRACoL 7, etc.) to help minimize variation.

5- Confirm that the proposed custom color is within the color gamut of the expected most used reproduction process.
An application like Chromix ColorThink enables the CIEL*a*b* values of the custom color to be compared with the color gamut of the system that will be used to print it and determine if it is reproducible or not - i.e. in, or out of, gamut.

If the custom color is within gamut, it means that it can be simulated by mixing screen tint percentages of the primary inks of the print process.

6- Make sure, by testing, that the ink pigments used in the custom color will not shift hue because of heat e.g. during lamination or react with other inks or to oxygen e.g. Reflex Blue.

7- Avoid using fluorescing agents in the ink.

8- Use certified sample color swatches and CIE L*a*b* values to communicate color globally.Ideally the sample swatches should be as large as possible since the perception of color changes with coverage area. Also include a "Hi-Lo" reference which shows how much darker or lighter the color can be and still be in specification. If possible, include a CIEL*a*b* Delta E value for how far the hue of the color can deviate while still being within specification. Include the information about how the Delta E value is to be calculated (e.g. Delta E 98, Delta E 76, Delta E CMC, etc.)

9- Prevent brand bloat by consolidating/rationalizing custom color libraries. Retire old colors and consolidate colors that are very similar.

A number of readers questioned my statement that humans have very good color discrimination for greens and less so for other colors. In the below video Eric Fossum, image sensor engineer and primary inventor of the CMOS sensor used in digital cameras, mentions the color sensitivity of the human eye during a recent talk at Yale University.

Sunday, July 3, 2011

I see halftones everywhere!

Technically speaking, halftone screens are "tessallations" - patterns that cover a surface by the repeated use of a single shape, without gaps or overlapping. And since tessallations are popular decorative items - I end up seeing halftone screens everywhere. Here are a few from a recent trip to Seattle.

A classic Diamond halftone dot

An example of a high lpi traditional Square dot halftone

In contrast to a very low lpi Square dot

Waiting to cross the street I spot a mix of two halftone patterns
At first it appears to be a classic Round dot mixed with a more subtle Square dot halftone
But on closer examination it seems to be an exotic version of Esko's Concentric screening. Interestingly the pixels that make up this sidewalk halftone are round instead of the traditional square shape.

Walking past this building reveals a fine example of
Second order FM/stochastic screening.
Sometimes the final halftone screen is not visible, but instead, you can see the foundation for the halftone. Halftone screen dots are formed by a "threshold" array - basically a pattern made up of 256 shades of gray which determines which pixels are turned on to form the actual dot.
The tones of the granite pillar on this building

Make a great threshold array to create a
Mezzotint halftone (the right half of the photo below - click to enlarge)