THINCK.com Colour Management service FAQ

1. What is a profiling service?
2. How do I use my profiles?
3. How many printer profiles do I need?
4. When do I need another profile made?
5. What type of device do we use to create profiles?
6. How often do we calibrate this device?
7. What Guarantee or Warranty comes with my custom profile?
8. I use Windows – can I still use ICC profiles?
9. Why can't I use my scanner as a color measurement tool?
10. How can I check the quality of a profile and can you show me which measurement systems create the best results?

What is a Colour Management service?

Colour management has a number of components of which ICC Color profiles are among the most important.

Some companies offer a custom profiling service to help color and black & white image creators get the most accurate color and most neutrally possible Black & White prints from their devices. High-quality profiles require measurements using spectrophotometers and calculations using the best software.

A good service can provide you with scanner color profiles and RGB, CMYK or Grayscale printer profiles. A full service,includes linearization of your printer if it is needed, and advice on steps to be taken for an efficient color management workflow.

If you use different batches of paper stocks or ink sets, you should realize that a new profile is needed for:

• each new batch of paper
• each batch of new ink
• each combination of paper, ink, ink density, and printing resolution.

A color profile is created by printing a test chart on the printer to be profiled.

• you should print a test chart on each type of paper you plan to use
• you should print a test chart with each type of ink you plan to use
• you should print a test chart for each combination of paper, ink and output resolution.

Each variation will result in a separate profile that you will use when printing with that setup.

Procedure

Open the correct profile target you received for your printer in Photoshop or other image-editing program. Select “Don’t color manage” when Photoshop prompts you.

• Print all the pages of the target from inside your program with all color management turned off, including image improving algorithms in the printer driver
• Carefully inspect the printout and ensure there are no blotches, spots, or any other problems on any of the color patches. Be certain that no scaling down or scaling up has been applied, and that all color patches, including all text on the target pages, have been included.
• Send the target pages in an envelope, making sure they can't be bent, folded, or torn, and take care not to staple them. If you really must, use paper clips to keep them together. Do not write anything on the front or back of the pages. If you must include comments or questions, include a separate page instead.

Make sure you follow the instructions carefully. If color patches are not smooth or equally covered, the test chart has been folded or creased, or any other flaw as mentioned above, it is impossible to measure your test chart.

How do I use my profiles?

Color profiles are very versatile and can be used in several different ways. They can be used to match colors so the image you scanned looks right on your monitor and prints correctly. Profiles from presses and other output devices can be used on a designer’s system to simulate the appearance of an image either on the monitor or on a printer. In some cases profiles can also be used to correct color problems in images.

Profiles are used anytime an image is transformed from one format to another. This is part of a color management workflow. So when you separate an RGB file to CMYK in Photoshop, an RGB source profile and a CMYK destination profile are used to calculate the separation.

How many printer profiles do I need?

As long as you are using the same inks and the exact same paper, you require the same color profile that was created for that combination of paper, ink and output resolution (and ink density in CMYK controlled workflows). But each time you use a different set of inks or another batch of paper, you should use a different profile. Remember that profiles are intended to “characterize” a printing process. If you change any part of that process and it has an effect on the colors produced, you need a different profile.

When do I need another profile made?

Your profile will remain valid until something occurs that changes the way your printer produces color. Changing the paper you use, getting a print head replacement, or buying your inks from a different manufacturer are all things that could invalidate your profile and require a new one to be made. Scanner profiles will remain good for at least 6 months.

If you print a lot, and therefore use different inks and batches of paper frequently, and you would nevertheless like to have the best possible color profiles, you should consider re-profiling.

What type of device should be used to create profiles?

We believe one should only use spectrophotometers from market leaders. Practically speaking, this means either X-Rite/GretagMacbeth, or Barbieri Electronic. Our favourite system is the GretagMacbeth iO as it provides unprecedented speed and ease-of-use.

How often do you need to calibrate such a device?

The device must be calibrated each time a test chart is measured.

I use Windows – can I still use ICC profiles?

All ICC profiles, if built properly, can be used on Mac or Windows computers. Your ability to use them depends more on your applications than the operating system. Most Corel and Adobe products correctly use profiles on both computing platforms. For others we suggest you consult your manuals and the manufacturer. Also, be sure you test your application’s use of profiles carefully. Not all applications use profiles correctly.

If you're working with Windows Vista, colour profiles are another matter, and we can't provide you with advice here, as we lack a Vista system ourselves.

Why can't I use my scanner as a colour measurement tool?

One approach to creating profiles on the cheap would be to use a colour scanner rather than a spectrophotometer. This is a no-go for several reasons. First of all, EFI owns a patent on this process.

In addition, it is prone to serious quality problems, because the color response of scanners rarely matches human visual response well. Some third-party tests with photographic reflective media and an Epson Expression 1680 indicate worst-case delta-E (the difference between the actual color and the meaured color) figures of about 9 for a best-fit linear model, the scanner having been calibrated and profiled properly.

The human eye can discern colour dfferences from approximately deltaE 1 to 3. In essence this means a scanner cannot be used for decent colour profiling purposes, even when it has been calibrated and profiled itself.

For complete background information on colour management, visit our online Magazine, IT Enquirer.