Tuesday, July 27, 2010

Choosing a CtP - some considerations

Focussing laser energy
The laser system that exposes the plate in a CtP system has an impact on the consistency of the halftone dots that make up the image on the plate and therefore the consistency and integrity of the final presswork. The more well focussed, and hence sharper, the beam of exposing energy the more consistent the resulting halftones will be.
The four main ways that laser energy is focussed on a CtP device in order from basic to most sophisticated:

1) Depth of field. This is the method most often seen used in internal drum CtP machines and film imagesetters. It is similar in concept to how depth of field works in a camera. Although a lens can precisely focus at only one distance, the decrease in sharpness is gradual on each side of the focused distance, so that within the depth of field, the unsharpness is imperceptible under normal conditions. Typically requires constant calibration to maintain imaging consistency.

2) Hard focus. The laser is focussed for the particular plate when the CtP system is initially set up. This method is not able to cope with issues of variations in plate media thickness or as plate surface to exposure focus point changes. Hot spots and/or banding may appear.

3) Auto focus. The laser does an auto-focus for the particular plate each time just before actual imaging begins. This method is not able to cope with issues of variations in plate media thickness or as the plate surface to exposure focus point changes. Hot spots may appear.

4) Dynamic auto focus. The laser continuously adjusts focus for the particular plate during actual imaging. This method is able to cope with issues of variations in plate media thickness or as the plate surface to exposure focus point changes. Hot spots are unlikely.

The "tape test"

To get an idea as to how well the focussing system is on a particular CtP device, simply make a large "X" using Scotch tape/Sellotape on the back of the plate. Image a 50% halftone screen across the entire plate. Remove the tape and process the plate.If, after processing the plate, the tape is visible in the 50% flat tone patch then you know that any variations in plate thickness, or plate surface to exposure focus point, that is equal or greater than the thickness of the Scotch tape/Sellotape will result in variation in halftone screen tones and therefore presswork. It's unlikely that in day to day production that you'd stick tape to the back of a plate before exposing it, however it is quite possible for a small piece of debris to land on the CtP drum or back of the plate during pre-exposure handling.

Ideally, the imaging integrity of the best system would not be compromised by the tape on the back of the plate and all you will see is a large flat 50% tone - no visible "X" pattern.

During the CtP manufacturing process the geometric accuracy of the CtP drum on which the plates will eventually be mounted and imaged is measured.

Geometric compenstion
Imagine a grid wrapped around the CtP's imaging drum.

In a perfect world the grid would have perfect integrity.

In reality - the drums are never perfect cylinders.

For those CtP devices that have this capability, geometric correction distorts the bitmap that will be imaged on the plate in order to compensate for differences in the geometry of the imaging drum on the CtP device. Geometric correction also provides CtP device to CtP device integrity so that the plates from different machines will be as identical as possible.

Thermal compensation
Aluminum plates expand and contract with temperature change as much as film does - about 0.5mm across a 1m plate (typical 8-page size) for every 5°C (9°F) temperature change.
That 5°C change in temperature will result in a half row of dots @ 175 lpi misregistration plate to plate which can result in the need for the shop to reimage all four plates in a process job even if only one is actually needed.
Plate imaged twice at different temperatures. Without temperature compensation, the change in plate size due to the ambient temperature change results in a misregistration of the image.

Thermal compensation, for those devices that have this capability, corrects for ambient temperature variations by scaling the bitmap in such a way that it is as if the plates were always imaged at a single temperature.

Thursday, July 22, 2010

QR Codes (2D Matrix Codes) - Reality check

If you're like most people in North America, you probably won't know what the above image represents, even though it is the latest craze being promoted to print service providers and marketeers.

"Matrix Codes," most popularly known as QR or Quick Response codes are essentially bar codes like the ones printed on package goods that are scanned at the merchant's checkout counter. QR codes take the notion a step further because they enable print media and web-enabled mobile media to work together. A QR code is a high-density barcode readable by smart cell phones and simple PC cams. By pointing the camera at the QR symbol, an application on the phone, or PC, opens the individual’s mobile browser and instantly connects them to a designated Web page without them ever having to type in a URL or promotional code - they just point and go. By scanning the codes, one can not only access websites but images, personal information, make phone calls, play a video, and send text messages.

QR codes are already a big part of mobile culture in Japan (where the technology originated in 1994) and South Korea with some 40% of mobile users in Japan regularly using their mobile phones to scan QR codes in advertisements.The marketing opportunities enabled by QR codes are limitless.

Advertisers, publishers and brand owners can use QR codes to add interactivity to any print media. In Asia (and slowly in the rest of the world) they are being placed on just about everything you could imagine - and some you wouldn't think of, like tattoos and gravestones.

QR codes explained in a clip from the television show CSI: New York.

Here are just a few examples of where you can find QR codes being used today:

• Business cards
• Outdoor posters and signage
• Packaging
• Clothing
• Newspapers and magazines
• Point of purchase displays
• Event registration

The reality check - at least for North American marketeers

While there seems to be a great deal of enthusiasm for the potential applications of QR codes, the state of the technology in North America is akin to the state of the internet for people who don't have a computer, or who do have a computer but have no ISP access. Sure the technology is great, however, from a marketing point of view, you've got to be realistic about your audience.

Today, with QR codes, you're only broadcasting to a small minority of the market:

1) They must have a smart phone or a phone for which QR reader applications are available - not just a phone with a camera. Right away that eliminates some 75% of the cell phone using audience.

2) They must be aware of the significance and value of QR codes. Try asking the technophiles at any cell phone kiosk to see if they have any idea what a QR code is. So ignorance going to remove, IMHO, at least 90% of the 35% of the market that have smart phones. So now you're down to maybe 3% of the market

3) They must download and install the QR software. That's work which many people shy away from. So maybe that cuts out another 50% of the market. So now you are down to maybe 1-2% of the market being able to use QR codes.

4) From a marketing perspective, you have to ask what percentage of that 1-2% of the total market is made up of your target audience (e.g. print specifiers)? 1%, 10%, 50%? I doubt that it's even as much as 1%.

Using a message delivery system that, at best, is accessible by only 1-2% of the total market and likely .001% of a given target market is not a message delivery system that I would count on to deliver a measurable, let alone significant, marketing ROI.

So, use and promote QR codes - but don't expect them to deliver an ROI as an effective marketing/promotional media. At least not today. However, once QR readers are pre-installed on smart phones and the major brands bring more attention to the technology QR coding will rapidly move from hype to "must have."Fortunately, the cost of entry is zero. You can create your own QR Code for any website, short text message, or other information using any one of the free online code generators like the one available HERE.

Tuesday, July 20, 2010

Wednesday, July 7, 2010

The Color Bar

Color bars (a.k.a. color control bars, color control strips, or proofing bars) are essentially test targets that are used to measure print and/or proof attributes. Normally, but not always, it is printed in the trim area of the press sheet.
Typical placement of a color bar on an offset press sheet - at the trailing edge (back end of the sheet).

However, it can take many different forms - sometimes hard to recognize - but always serving the same purpose.

Sometimes the "color bar" is incorporated within the graphic design of the publication. In this case the color makeup of the title (Cyan) and section headers (Blue, in this example, - Magenta overprinting Cyan).

Sometimes it is hidden in the spine (in this case the grey line running from top to bottom on the front edge of the photo).

While it is certainly possible to measure the color of the actual live image area, the technology is expensive and, as result, few printers are fortunate enough to have it at their disposal. Also, measuring the live image area doesn't provide as much useful information as a color bar can. Color bars therefore act as proxies, or substitutes, for the live image area as well as provide additional data.

The logic behind color bars

1) Unlike the live image area of the press sheet, color bars are consistent job to job. Therefore they are more efficient at providing a benchmark and can be used to track trends in variation over time.

2) Color bars can be tailored to meet the needs and measurement capabilities of individual print shops.

3) Color bars may be used to measure all aspects of the "print characteristic" - solid ink density, overprinting (ink trapping), dot gain, grey balance, as well as issues such as slur and dot doubling.

4) Color bars can reveal issues with ink hue, blanket condition, impression cylinder pressure, etc.

5) They can be used forensically to help understand why a specific job did not meet expectations.

6) They are efficient since, unlike the live image area, they are a constant made up of well defined elements that continue from proof to press sheet.

Solid ink density
A printing press is essentially a complex machine for laying down a specific film thickness of a specific color of ink onto a substrate. The ink is metered out in zones across the width of the press sheet according to how much ink coverage is required for each color in each zone.Therefore, for most press operators, the minimum requirement for a color bar is that it contains solid patches of the inks that will be printing since solid ink density is the only thing on press that an operator can adjust while the press is running.Those solid patches are then repeated over the width of the press sheet so that each ink zone is represented by at least one complete set of patches - containing one patch for each color being printed.
Information provided by only using solid ink density targets in the color bar
In this example, cyan is misregistered while the black printer is over emulsified (fountain solution breaking down the ink).

1) Provides a solid ink density value, measured using a densitometer, to determine if the press sheet is conforming to published industry, or shop specific targets.

2) Is an indirect, but practical, method of determining optimum ink film thickness and hence the balance of maximum color gamut without introducing image degrading inking issues such as slinging/misting.

3) The balance of the primary solid densities determines the hue of the overprints - i.e. the SID of magenta and SID of yellow determine the hue of the resulting red.

4) Indicate misregistration which can then be examined in the live image area.

5) Reveal defects such as slinging/misting/tailing, over emulsification, slur, doubling.

6) If records are kept, the hue of the ink currently on press compared with the hue of ink used in the past to determine if there is any contamination, change in color due to ink batch differences, etc.

Forensic targets on color bars are image elements that are typically not measured by the press operator unless there is a problem in aligning presswork to the proof. If that happens then these targets may provide useful information as to the cause of the problem.

Two-color overprint ink trapping targets
Ink "trap" is an objective indication of the ability, or inability, of a printed ink to accept the next ink printed compared with how well the substrate accepted that ink. Poor ink trapping results in presswork color shifts in reds (magenta plus yellow), greens (cyan plus yellow), and blues (cyan plus magenta) as well as a loss in total color gamut.
The two-color overprint solids allows for the objective measurement and evaluation of ink trap efficiency as well as the overprint hue error and greyness.
Typical trap values for three print conditions running a CMY ink sequence with Black first or last down:
Offset sheetfed: R=70, G=80, B=75
Heatset web offset (publications): R=70, G=87, B=72
Coldset web offset (newspaper): R=50, G=89, B=50

Slur and doubling targets
Slurring and doubling are print defects that occur when halftone dots and type blur as a result of a slight second contact or movement between press cylinders or the paper and blanket. (More about slur HERE and doubling HERE)
There are many different styles of slur and doubling detection targets. Here are two of the most popular:Of course, every halftone dot or letter character on the printed sheet will reveal slur and doubling, however the targets in the color bar signal the defect easier and quicker.
Grey balance targets
Grey balance targets are made up of a patch of three screened process colors that are balanced so as to appear as neutral grey under standard printing conditions. They are typically printed adjacent to a black screen tint of a similar value to allow for a quick visual, or measured, evaluation of how grey balance has shifted.Grey balance targets can be useful since variation in any of the three process colors because of dot gain, slur, doubling, density, trapping, and registration will be reflected by a shift in hue away from neutrality. The 3/C patch will take on a bluish, reddish, or greenish color cast.The idea behind this target is that any grey balance color shift away from neutrality suggests a possible color shift in the live image area. However, in production printing the grey balance target may not be a reliable indicator of presswork issues.

Other targets
Other targets that may be included in the color bar are:

Dot gainThese targets are intended to capture dot gain variation information. The dot gain targets may consist of just two patches for each process color to measure the dot gain a one location on the tone scale, or, with the addition of more patches, to measure the dot gain at the quarter, mid, and three-quarter tone values. Dot gain can be useful because issues like slur, doubling, or incorrect solid ink density, will be reflected by a variation in the measured dot gain.

Brown balance targets
Brown balance patches are similar to grey balance patches in function except that they are made up equal percentages of cyan, magenta, and yellow. Unlike grey balance patches which allow the press operator to make a subjective visual assessment of hue shift, brown balance patches can only be evaluated objectively with instruments.

ProprietaryProprietary targets such as that used by System Brunner are typically used to drive on-press closed loop color control systems.

Spot colorIf a spot or brand color is being used then it will warrant at least a solid patch in the color bar so that its solid ink density can be measured. Space permitting, the solid patch will be adjacent to a screened back patch so that dot gain information can be measured.

For process control, color bars should be included on every proof and press form of every job. If that is not possible because there is no room on the sheet (as often happens in newspaper work) then there are several options;

1) Run color bars on occasion by including it in the live image area.With the publisher's permission if required.

2) With the print buyer's permission, incorporate color bars test elements into the graphic/editorial design of the printed piece (see the USA Today example in Part 1).

Color bars are not a requirement for quality printing, however, they are key to making proofing and printing more efficient and effective while reducing overall production costs.

Presswork should be run "to the numbers" i.e. the solid ink density aim points, at which time the presswork should align to the signed-off proof. At that point the press operator should be free to make any needed ink key adjustments to refine the match. The color bar then becomes a record of initial match and needed adjustments. That information can be used in statistical process control to spot any trends, or issues, revealed by the kind of ink key moves that are made over time.

Color bars can be placed anywhere that they fit on the press form, including the lead and trailing edge as well as across the center of the form. In fact, placing it in the center of the form parallel to the inking rollers is ideal, since there is less likelihood of seeing the variation that occurs at the lead and trailing edges. Color bars can even be placed in the gutter inline with the direction of the sheet through the press, although doing so is not optimal since it provides information from only one ink key zone.

Ideally the color bar should use the same halftone screening as the live image area and have had the same press curve applied.

Friday, July 2, 2010

The Wayback View – Making a newspaper - 1944

The making of the Star Journal and Minneapolis Tribune newspaper from original art to final presswork.
Preview images from the video


Please press the play arrow to view the video. Note that it may stop for a moment while the video buffers in the background.

Today's Star Tribune is the product of the merger in 1982 between the Minneapolis Star, an evening newspaper, and the Minneapolis Tribune, a morning newspaper published by the same company.
In March 2007 Par Ridder was named Publisher of the Star Tribune, after his predecessor, J. Keith Moyer, decided to leave the newspaper after the sale to private-equity firm Avista Capital Partners. Ridder, who resigned on December 7, 2007 is a member of the Ridder family that had owned Knight-Ridder, the publishers of several newspapers including the rival Saint Paul Pioneer Press. Ridder's arrival resulted in considerable litigation when it was discovered that he had stolen a hard drive which was Pioneer Press property. This hard drive was laden with information about employees and advertisers which the Pioneer Press characterized as "trade secrets". Ridder also took two high-ranking staff members with him to the Minneapolis paper.
On January 15, 2009, as the nation's 15th largest daily paper, the paper filed for Chapter 11 bankruptcy.