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The Imation Rainbow™Color Proofing System Visual Color Calibrator v1.0 (VCC) is designed to be used as a simple visual guide to optimize the color match between your Rainbow™ proof and the 3M Matchprint™ color proofing system proof. It allows all users the opportunity to "fine tune" the Rainbow™ system for best possible output, without being a color expert.

Tech Service offers the following information to help you and your customers effectively use this tool for best possible results. Detailed instructions for the VCC are included with the tool.

What is the Rainbow™ VCC?

The Rainbow™ VCC adjusts for best three-color (YMC) neutral gray. Users can add/subtract black numbers as desired after successful completion of the visual calibration procedure.

The VCC consists of the following:

• Macintosh™ or DOS diskette containing the following files:
  
  • Calibrator.PS (PostScript™file)
    
  • Worksheet
    
  • Instructions for using the VCC
• Matchprint™ III Target Strip

The Calibrator.PS file is output on the Rainbow™ system and is composed of the following:

• Five multi-color gray level grids for adjusting overall gray balance with the Matchprint™ target strip
  
• CMYK / RGB grid of 3, 5, 25, 50, 75, and 100 percent tints
  
• Gray balance grid
  

The Worksheet can be used to record the numbers that will be used in the Rainbow™ system software Color Calibration table. (Double-click the Worksheet file to open it and send it to the printer.)

The Matchprint™ III target strip, consisting of five three-color gray level squares is constructed with a YMC laydown sequence, Commercial colors on Matchprint™ Commercial base.

Each Matchprint™ target strip square corresponds to a signal level adjustment: 16, 64, 128, 196, or 255. The multi-color gray level grids in the Calibrator.PS file also correspond to these five signal levels. Signal levels are sent to the Rainbow™ proofer to generate the desired color for specific tone values.

When is the Best Time to Use the Rainbow™ VCC?

The best time to use the VCC is when changing ribbon lot numbers ­ after calibration numbers for that ribbon lot have been entered into the Rainbow™ controller software. The Rainbow™ controller software has a color calibration utility that allows you to refine the color proofing characteristics of the Rainbow™ system.

Imation tests each new lot of ink ribbon as it is manufactured and provides users with a starting point of calibration numbers via the Imation C.A.R.E. Center or the Rainbow™ Bulletin Board System (BBS). These numbers provide all but the most critical color users with acceptable color output. The VCC is used to further "fine tune" the Rainbow™ system.

The Procedure at a Glance

The user sends the Calibrator.PS file to their Rainbow™ proofer. He or she then takes the proof to a viewing booth and uses the multi-color gray levels in this proof to match to the corresponding neutral gray levels on the Matchprint™ target strip. The user then changes the calibration numbers as indicated by the match and resends the Calibrator.PS file. This procedure is repeated until a close match is obtained between the center squares of each grid block and the corresponding square on the Matchprint™ target strip. It generally takes up to 3 iterations to come to a close match.

When Performing the Procedure...

Note: Below is a summary of the procedure along with some tips from Tech Service to help you get the most from the VCC.

Before you Use the VCC.

• Make sure you have entered the calibration numbers for the ribbon lot into the Rainbow™ controller software.
• Because the Matchprint™ target strip is made using Matchprint™ III system materials, it is best to select the Matchprint™III Commercial target in the Rainbow™ v3.0 software, or Commercial from any version of Rainbow™ software before v3.0. Select this target in Preferences under the File menu.

1. Send the Calibrator.PS File to the Rainbow™ Proof.

• Output the Calibrator.PS file from the Rainbow™ proofer.
• After the Calibrator.PS file prints, take the proof and the Matchprint™ target strip to a viewing booth.

IMPORTANT

Make sure you view the proofs under 5000°K lighting! Colors created by pigments on the Matchprint™ base material and by dyes on the Rainbow™ base material may appear significantly different under different lighting conditions and affect your perception of color.

2. Compare the Rainbow™ Proof to the Matchprint™ Target Strip ­ Find the Closest Match.

• At the viewing booth, slide the Matchprint™ target strip over the squares in the Level 16 grid on the Rainbow™ proof while looking through the viewing hole in the target strip. Compare each color square in the Level 16 grid to the Level 16 Matchprint™ target strip square and find the closest match.
• When you believe you have found the square in the grid that comes closest to the Matchprint™ target square, move the target strip above, below, and to the left and right of that square, making sure it is the nearest match. Mark that color square with a fine point marker through the target strip viewing hole.
• Repeat for each remaining gray level (64, 128, 196, and 255).
  Note: Level 16, the "highlight" grid will be the most difficult to match as movements of one number over and over can mean that you are just chasing the low noise level of color onset.

3. Enter Numbers from the Proof into the Rainbow™ Controller Software.

• After marking the color square for all gray levels (16, 64, 128, 196, 255), enter the numbers shown under each marked square into the Color Calibration window of the Rainbow™ software, algebraically adding these numbers to the existing numbers you already entered for your particular ribbon lot.

  For example: If Level 16 cyan is -3 in the Color Calibration window and the number you marked on the Rainbow™ proof is -2, the new number you will enter is -5.

4. Send the Next Iteration(s) of the Calibrator.PS File to the Proofer Until a Close Match is Achieved

• Repeat steps 1-3 until the best match from the Matchprint™ target strip to the Rainbow™ proof is to one of the center nine blocks of each grid. Normally, it will require no more than 3 iterations to get to the best match.

  TIP
  The Matchprint™ target strip's best match to the centers of the Rainbow™ proof grids may not be a perfect match; it only needs to be the best match. In fact, a 'perfect' match at every grid level probably means that the user has stretched the capabilities of the dye system to try to compensate visually for those differences, and there is a chance that full gamut colors will have problems in different areas of the jobs produced later.

5. Adjust Density (Optional)

• Adjusting Weight of a Particular Area of the Proof
  After you have used the VCC to get the best grid match, you can experiment with adjusting the weight of a particular area by moving all numbers in that area (16, 64, 128, 196, or 255) up or down 2 or 3 numbers equally for each color.
• Matching Overall Density between Two or More Rainbow™ Proofers
  The Proofer Density Compensation option in the Color Calibration window of the Rainbow™ Controller Software allows the user to match overall color density of two or more Rainbow™ systems. It also can be used to add to or subtract from overall saturation of the proof, but the proofer may then not be a good density match to another proofer.

  This will adjust all areas of the proof equally ­ from highlight areas to shadow areas. If weight adjustments are needed in only one area, do not use the density adjustment.

After Using the Rainbow™ VCC...

For Critical Color Accounts

The VCC, properly used, will get most users to an acceptable color prediction of a properly made Matchprint™ proof from known good films. For critical color accounts, some additional "tweaking" can be done from visual assessments made to a proper test target.

• After achieving the best match with VCC, output a Rainbow™ proof of a known test target that consists of a balanced mix of general scans covering the normal YMCK printing gamut of colors, a gray balance strip similar to the one on the VCC, and a rendition chart of primary and secondary colors. Then make a Matchprint™ proof of the same target.
• Compare the Rainbow™ proof and the Matchprint™ proof. Again, as when using the VCC, the goal should not be "Picasso Color Perfection," but rather the best reasonable visual match.

• It is never advisable to chase one particular color area on the test target without watching the gray balance strip to make sure you don't drift too far from your best VCC match.

  If you find your Rainbow™ color calibration window is "maxed out" at 11's and 12's in several areas, it probably means that you overadjusted first in one area, and then had to overadjust in another area to compensate. It would be better at this point to clear out and start over with the original ribbon lot numbers and the VCC.

• Using the same test target continually will allow you to become familiar with all areas of that target and which "handles" in the Rainbow™ Color Calibration window to adjust to make minor color adjustments.

Note: St. Paul Tech Service has created test targets, "Rainbow™ Test Form," that meet the above criteria. They are available in PostScript™ format for direct output to the Rainbow™ system and also in QuarkXPress™ format so users can create their own Matchprint™ test targets from film. The file name for the test targets is: RB_TFORM. Imation sales representatives can obtain this file by calling the Imation C.A.R.E. Center (800-328-1303).

Summary

• Follow the VCC instructions to obtain the best match between the Rainbow™ grid file and the Matchprint™ target strip.
  
• All viewing should be done in a 5000°K light booth.
  
• Don't be overly critical, the VCC works best as a quick and easy tool.
  
• Remember that the density compensation adjustment affects all areas from highlight to shadow. You can adjust weight in one area by moving all numbers at any level: 16, 64, etc., equally.
  Note: Small adjustments of two or three numbers are best,gross adjustments can affect other areas above or below the one being adjusted.
  
• As soon as the best match for each level grid is one of the center nine squares, stop and output a test target if desired.
  
• You should make only minor secondary adjustments using your test target, always maintaining a reasonable gray balance.

Important Notice to Purchaser:

All statements, technical information and recommendations contained herein are based on tests Imation believes to be reliable, but the accuracy of this information is not guaranteed.

Limited Warranty and Limitation of Remedies:

Imation warrants only that the Imation Products described above will meet the published warranty applicable to said Imation Products. THIS WARRANTY IS MADE IN LIEU OF ALL OTHER WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
LIMITED TO THE IMPLIED WARRANTY OF MERCHANTABILITY, THE IMPLIED WARRANTY OF FITNESS FOR ANY PARTICULAR PURPOSE OR ANY IMPLIED WARRANTY ARISING OUT OF A COURSE OF DEALING OR OF PERFORMANCE, CUSTOM OR USAGE OF TRADE EXCEPT OF TITLE AND AGAINST PATENT INFRINGEMENT.

If any Imation product is found not to meet the above-stated warranty, Purchaser's exclusive remedy and Imation's and/or Seller's only obligation is to repair, replace the product or refund the purchase price, at Imation's or Seller's option, within a reasonable time after written notification but no later than sixty (60) days after discovery of the defect, all as specifically stated in Imation's published warranty. Imation WILL NOT UNDER ANY CIRCUMSTANCES BE LIABLE FOR ANY INDIRECT,
INCIDENTAL, SPECIAL OR CONSEQUENTIAL DAMAGES (INCLUDING BUT NOT LIMITED TO LOSS OF PROFITS, REVENUE, OR BUSINESS) IN ANY WAY RELATED TO THE 3M PRODUCTS, REGARDLESS OF THE LEGAL THEORY ASSERTED.

Imation, Rainbow, and Matchprint are trademarks of Imation Corporation
Macintosh is a trademark of Apple Computer, Inc.
PostScript is a trademark of Adobe Systems, Inc.
QuarkXpress is a trademark of Quark, Inc.