When it comes to managing color, some newspapers act like a dog chasing its tail. Often, there's a big communication gap between the pre-press and press departments. Press operators tweak their settings to accommodate changes from pre-press, while the pre-press people make adjustments to chase the press. And around and around it goes.
To stop running around in circles, you need consistency. If you can accurately reproduce an 18 percent dot, and you're confident that the dot is going to be 18 today, 18 tomorrow, 18 next week and 18 next month, then you're in control. Only then can you start working on some of the finer adjustments that produce true color quality.
Finding this level of consistency is getting tougher all the time. The recent shift toward open systems has forced us to become systems integrators. It is now up to us to pull together all the components and make them work effectively. Doing so requires us to understand not only hardware and software, but also basic reproduction and color separations.
We need an approach that can control the process from beginning to end. This involves charting the entire pre-press and press operation and then developing a specific procedure for each and every step.
How should we operate each piece of equipment in our process flow? Which settings should we use? How should we maintain our equipment? How should we set it up? How can we check to verify that it's working properly? These questions are at the very heart of sound quality control.
One fall Sunday in the early 1960s, after his Green Bay Packers had been trounced 73-0 by the Chicago Bears, coach Vince Lombardi decided his team needed to get back to basics. He assembled his troops in the locker room, held up an oval leather object and said, "Gentlemen, this is a football." From there, he began retraining his players in the basics of blocking and tackling, and built the fundamentally sound teams that won the first two Super Bowls.
If I could assemble all newspaper people who are having problems with color quality, I might say, "This is a densitometer, and this is a calibration plaque."
If you don't have both reflection and transmission densitometers that work, then you don't have the proper tools to even consider quality control. And if you don't have an up-to-date calibration plaque, your densitometers won't be accurate enough to help you. I recommend changing your plaque every year (See related story, The Guts of a Densitometer).
Of the 20 or so newspaper sites that I visited over the past year, 15 or 16 either had faulty densitometers or couldn't find their calibration plaques. They simply made their adjustments from day to day through trial and error. They were chasing their tails.
We want to evaluate the key components of our system, but where do we start? At the one piece of equipment that we can evaluate in and of itself--the film processor.
The way to calibrate a film processor is to process a control strip. This checks three major variables--speed, temperature and chemical concentration. When you run the control strip through the processor's chemistry, you can tell whether or not the chemistry is up to snuff for each given speed and temperature.
Several vendors make control strips, and one has a product that's specific to the hybrid, rapid-access chemistry that virtually everyone now uses.
If you don't want to buy a control strip, you can make your own. Simply take a point in time when you're getting good results and run off several exposure scales from your imagesetter. Before you process them, slice and dice them into predetermined lengths in your darkroom. Then put them in a film box in your refrigerator.
After you're confident in your film processor, you can work your way back to the imagesetter, raster-image processor--all the way back to the photographer's camera.
If your imagesetter has a self-test mode, you can hit a button and it will output a checkerboard pattern. Run the pattern through the already-calibrated film processor. Take a look at the pattern with a loupe, and make sure that the corners on the square dots are touching.
To calibrate your RIP, the first thing that you need to do is print an uncalibrated job. Then measure your values throughout the tone range with your calibrated densitometer and enter those values back into the RIP workstation.
After that, you can do some tweaking, if needed, and print out a calibrated strip to verify that your tweaking was successful. If you're outputting to film, you usually won't need to tweak, but if you're outputting to paper, you will.
You should check the RIP every day and make sure you're within a percent and a half of the scale. The manufacturers' specifications are 2 percent, and that's fine once you get into shadow areas. But in the highlight and quarter tones, if you're more than a percent and a half off, then you can start having problems.
Some newspapers are in a transition period, outputting from their imagesetters to both paper and film. Often, paper halftones require different size dots or tone adjustments than film halftones.
NAA advises getting around this problem by outputting your calibration scale to paper, shooting that on the camera, and then measuring the resulting film. Enter those film values back into the RIP workstation. Then you can not only compensate for the paper output on the imagesetter, but also for the dot loss that typically occurs in highlight areas and the dot enlargement that occurs in shadow areas at the page camera.
Further back in the process, you need to look at the workstations running pre-press applications. With today's sophisticated software programs like QuarkXPress, Photoshop, Freehand and Illustrator, it's possible that the dot values displayed in the application won't be the dot values requested at the RIP workstation.
You can output a basic step scale (11 steps or 21 steps, in 5 percent increments) from each of these applications and pass it from the workstation through the RIP, imagesetter and film processor to verify that your page setups are not somehow manipulating the images.
This is necessary because transfer curves sometimes are included in the application. Or it may be that a transfer curve is built into the Postscript page description for a particular output device within a given software package. In QuarkXPress, for instance, you have the possibility of selecting or using EfiColor profiles. These are merely transfer curves that are trying to second-guess what is required by your press. So they actually make adjustments to all of your TIFF files that are placed in QuarkXpress.
After you go through each step of your process and fully understand how to control and manipulate images and accurately predict your dots throughout the tone range, turn EfiColor off. This is because you should adjust your images only in Photoshop during the scan to correct for the press.
To modify your ink-preference settings in Photoshop, first take a picture of a MacBeth color checker. Scan the picture, and then move the image through your RIP, imagesetter, plate processor and press. Measure the press results, and then go back to Photoshop to modify your ink settings.
One challenge is that there are so many different ways to achieve the same end result, and we're given too many choices. With so many choices, people will sometimes say, "I'll take this one and this one and this one," and all of those transfer curves either build on themselves or conflict with one another. The result is that your process becomes unpredictable.
I'd love to see applications like Photoshop include a supervisor or manager function, where you could set up each workstation and then remove the ability to change it. To change a profile, the user would have to see the network administrator.
Now on to the photographs themselves. They can enter our system from a variety of sources: overseas correspondents, photo services, advertisers and even readers. Typically, we don't have much control over the quality of these pictures. We can, however, put some procedures into place to help our staff photographers.
From a pre-press perspective, it would be nice if we could standardize the way pictures are taken, but in reality, photographers take pictures under a variety of different lighting conditions--indoors, outdoors and in the local high-school gym lit by a 60-watt bulb screwed into the ceiling. They also use different types of film: high, medium and low speeds, Fuji and Kodak emulsions.
One way to gain control is to give your photographers a MacBeth color checker and have them shoot it at the beginning of a roll. You can then measure the output with a densitometer and adjust the density curve in Photoshop until the output matches the original.
If you have specific rooms where you shoot pictures all the time, like sports arenas or city hall, you can set up a number of profiles in Photoshop to address all of the lighting conditions in combination with various film speeds and emulsions. You can then save those profiles in the scanner workstation and apply them when you have a picture that was taken in a particular room.
How can you identify a problem with your scanner? There are two approaches.
An IT-8 target is a standardized series of patches with predetermined values. You can scan it to find out if your color is off and by how much. Then you can make some pre-scan adjustments and save them as your default profile for future scanning.
You can also use a MacBeth color checker. Scan the color checker, and then set your gray values. Just set a white point on the white and a black point on the black.
When I did this recently, I found that my scanner was off in the red channel by about 10 percent. So I saved the adjustment that I made to set white and black, which basically neutralized my gray scale, as my default curve. Now anything I scan on my flatbed is a lot closer than it was before I tried my little test.
Now it's time to move from the film processor in the other direction, toward the press.
You should measure the output of your page camera with your calibrated transmission densitometer and assign a value to it when conditions are right. And when are conditions right? When you are running a Dmax higher than 4.0. Running a lower Dmax throws off dot accuracy because you get more fringe values on the perimeter of the dots that get burned through when you're exposing plates. The type might look all right, and some of the large solids might hold well, but you won't have sufficient Dmax to hold your dot integrity.
Further along in the process we get to the platemaker. Many people use a continuous-tone Stouffer scale as a plate guide. Make sure that yours is current. When was the last time you replaced it?
When you first purchase both your reflective Stauffer scale and your transmissive Stauffer scale, check their densities. Then check them on a weekly basis to make sure their densities are not fading or otherwise changing. Once they start fading by more than, say, .05 density units, then replace the scale.
A better exposure scale to use in platemaking is the UGRA scale, which tells you a lot more than a continuous-tone step. It gives you an indication of what resolution your plate is capable of holding, and it also tells you where you can hold your smallest highlight and your darkest shadow. After printing it on press, you can also use it to tell the pre-press people what settings they should use for half-toning.
If you can get close to a solid four or five on the continuous-tone portion of the UGRA scale, often you'll be able to hold a micro-line resolution of about 10 or 12. If you've ever seen the micro-line scale, it goes from four all the way up to 45 or 50, so holding in the 10-to-12 range is really good. Many plate manufacturers will recommend that you burn the plate a lot longer so there won't be any possibility of plate wear, but doing so decreases your ability to hold fine detail.
One way to verify whether a plate has been properly exposed is to use control patches. If you're paginating with QuarkXpress, for example, you can put control patches on the bottom of the page. Place five patches--at 5, 25, 50, 75 and 95 percent--just below the area where the plate bends, so that when the plate is hung on press, the patches fall in the bend area. Then if there's a problem and you want to verify that the plate was properly exposed, you can take the plate off the press, iron out the crease and measure the five patches.
To measure those dots on the plate, I recommend having the right tool. In this case, it's a high-powered microscope with a very precise reticule. Some people say you can measure plates with a reflection densitometer, but the secret is you've got to know the right N, or fudge, factor. How do they come up with that N factor to plug into the densitometer? They look at it with a 100-power scope. So why not eliminate that step altogether and measure the dots with the scope?
Now on to the press. The key here is to test your press every six months or so using a press-test form.
NAA, GATF and SNAP all make test forms. Their one drawback is that they test only the press and, to a certain extent, the plate and the film processor. So NAA also recently put together a digital test form that can help you test equipment all the way from the pre-press software (available at http://www.naa.org). The file is in Adobe Acrobat format and fits on a floppy disk.
The form has a 21-step scale in black that goes from zero to 100 in 5 percent dot increments. Output the first page, or the first plate, which is the black plate, through your application, RIP, imagesetter and film processor, and then measure it to verify that everything is properly calibrated.
The form has another area in the middle that focuses on midtone values. Set up your RIP to generate a square dot pattern. Typically, on a negative-working offset plate, you'll have about a 2 percent gain in the midtone. You can verify this by looking at the 48 percent dot patch--based on a square dot screen, the corners of the dots should be touching.
Down at the bottom, there's a color bar that has a series of patches you can place in a scanning densitometer and get just about every characteristic of your reproduction on press. This gives you a quick footprint of your printing process.
The other critical parts of the test form are the gray-balance patches--a series of CMY circles blended into a black-only background. They include areas for highlights, quarter-tones, midtones and three-quarter tones.
They provide invaluable information. You can pass them to the pre-press department, so those people can establish a tone curve on the pre-press equipment to give you gray balance all the way from light tones through midtones to dark tones.
Once your press is calibrated, you should keep tabs on it by using color bars. USA Today, for example, supplies the press with solid overprint bars to help them control their color on editorial section fronts.
The problem with running solid bars is that they don't necessarily guarantee that your tonal ranges, which are not solid, are going to be balanced. The area of the tone curve that you need to focus on is the quarter-tone portion, because that's the area that contains the greatest amount of detail information in the picture.
For this reason, you should run quarter-tone gray bars across your page. Even this, however, is not the total solution. Quarter-tone gray bars can also give you problems, because they do not monitor the solids.
The best solution is to use a quarter-tone gray bar coupled with a three-quarter-tone gray bar. You can use this combination to troubleshoot your press, and when the press settings are correct, you'll be able to achieve both a neutral-gray quarter tone and a neutral-gray three-quarter tone.
This clearly identifies where the problem is. Say a picture has a green cast to it. If the gray bars are both neutral, then you have a pre-press problem. If one of the gray bars is off, then it's a press problem. You can see it right on the page.
To summarize, if you want to get good quality, you need to map out the process flow at your particular operation and then develop standard operating procedures for each major component. These SOPs should include guidelines for setting up, operating and maintaining each piece of equipment. Also, include a quality check for each procedure. This verifies that the procedure was carried out properly and lets you go on to the next step with confidence.
Finally, make sure you have people in your organization who really understand your process from front to back. Such people can help you get your process under control. They can train your crazy dog to sit up and bark on command--and stop running around in circles.
Tom Croteau is NAA's director of newspaper services. E-mail, crott@naa.org; phone, (703) 648-1213; fax, (703) 648-1333.
©1997 Newspaper Association of America. All rights reserved.