Note: The "Gamut Check" step will be skipped when running an inline spectrophotometer in Automated mode. When using the inline spectrophotometer, keep it in Manual mode until after the "Gamut Check" step.
The purpose of this step is to check the color measurements for the gamut of Media Configuration components so far, such as: media, printer resolution, spectrophotometer measurement condition, usage, and Total Ink Limit value.
The software uses the measurements from the Single Channel Ink Limit chart to compute initial gamut statistics. It compares the results to historical data for each Usage Type, and computes a "PASS" or "Warning" answer. A pass indicates that initial data looks good for this media configuration, so it is recommended to continue. If a "Warning" is computed, it is recommended to take a few minutes to make sure you have selected the right components in this media configuration. see "Troubleshooting a Gamut WARNING message" section below. You can always choose to continue, no matter what the gamut results are.
Estimated Media Config parameters:
eminL* = estimated minimum CIE L*,
eMYC* = estimated maximum CIE C* of the Magenta-Yellow (MY) overprint,
eCYC* = estimated maximum CIE C* of the Cyan-Yellow (CY) overprint,
eCMC* = estimated maximum CIE C* of the Cyan-Magenta (CM) overprint,
maxa* = estimated maximum CIE a* and max ink percentage value,
maxb* = estimated maximum CIE b* and max ink percentage value,
emina* = estimated minimum CIE a*,
eminb* = estimated minimum CIE b* and min ink percentage value,
estGamutVDiff = estimated Gamut Volume Difference from Selected Target Profile.
Target Profile parameters:
PminL* = actual Profile minimum CIE L* value,
pMYC* = actual Profile maximum Magenta-Yellow overprint CIE C* value,
pCYC* = actual Profile maximum Cyan-Yellow overprint CIE C* value,
pCMC* = actual Profile maximum Cyan-Magenta overprint CIE C* value,
Pmaxa* = actual Profile maximum CIE a* value,
Pmaxb* = actual Profile maximum CIE b* value,
Pmina* = actual Profile minimum CIE a* value,
Pminb* = actual Profile minimum CIE b* value,
estProfGamutVolumeDiff = estimated Gamut Volume Difference from Selected Target Profile,
estSpotGVolumeDiff = estimated Gamut Volume Difference from a Spot Color Gamut Volume.
Media Configuration Gamut Tests:
(1) high minimum L* - the minimum L* value of your Media Configuration is too high. High values can result in spectrophotometer measurement failures, or inadequate contrast in output images.
(2) poor paper white - the media/paper color measurement (CIE L*a*b*) is too far from the color measurement of the Target Profile. A color simulation cannot be accurate enough if the color of the paper is too far from your Target Profile.
(3) low gamut volume - the estimated Gamut Volume is too small compared to your Target Profile, with the selected usage.
(4) poor 2color overprint C* - the 2-color overprint CIE C* estimated value is too far from your Target Profile.
Example of Information displayed with a "PASS" (you must scroll down to see all of the information):
**** PASS **** Estimated Gamut results pass for Color Standard (Best Color Consistency)
Estimated Media Configuration Results: (eminL*: 1.57), (eMYC*: 106.69), (eCYC*: 85.38), (eCMC*: 85.28), (maxa*: 82.79 M_81), (maxb*: 117.26 Y_100), (emina*: -73.96), (eminb*: -67.02 C_63), (estGamutVDiff: 1019469),
Target Profile Results: (PminL*: 8.06), (pMYC*: 83.9), (pCYC*: 72.84), (pCMC*: 49.25), (Pmaxa*: 74.12), (Pmaxb*: 93.16), (Pmina*: -68.42), (Pminb*: -46.15), (estProfGamutVolumeDiff: 1019469), (estSpotGVolumeDiff: 147626)
This Media Configuration looks good so far! Note that some color standards require the paper measurement value to be within 1.5 CIE dE00, whereas this only checks that the value is within 3.0 dEab. You might want to check the paper color difference value in the dialog in this situation.
Example of Information displayed with a "Warning" (you must scroll down to see all of the information):
*** WARNING *** Estimated Gamut results not suitable for chosen Target Profile and Usage: Spot Colors (Largest Color Gamut).
Media Configuration fails for: (2) poor paper white. Click ? for more information.
Estimated Media Configuration Results: (eminL*: 1.57), (eMYC*: 106.69), (eCYC*: 85.38), (eCMC*: 85.28), (maxa*: 82.79 M_81), (maxb*: 117.26 Y_100), (emina*: -73.96), (eminb*: -67.02 C_63), (estGamutVDiff: 1060811),
Target Profile Results: (PminL*: 9.05), (pMYC*: 83.23), (pCYC*: 70.93), (pCMC*: 50.18), (Pmaxa*: 75.0), (Pmaxb*: 92.99), (Pmina*: -66.0), (Pminb*: -46.02), (estProfGamutVolumeDiff: 1060811), (estSpotGVolumeDiff: 147626)
This Media Configuration failed for its measured Paper white Value. The paper color measurement was too far from the Target Profile. This can be corrected by choosing a different media, spectrophotometer measurement condition, or in some cases by printing an ink tint value on the output (usually only a Yellow ink tint value is considered visually acceptable).
Troubleshooting a Gamut WARNING message:
Did I choose the right Media / paper?
If the intended use of this media configuration is for high quality color output proofing (usage choices: COLOR STANDARD, SPOT COLORS, or COMPROMISE), The paper white of your media configuration should be within 3.0 CIE dE00 of your color standard profile, and the color gamut estimate should be large enough. Proofing quality papers only. Photographic quality papers do not have a stable enough white point (CIE L*a*b* value) for high quality proofing.
If the paper white value is larger than 3.0 dE00, you might want to try a different spectrophotometer measurement condition. (see below). If the measurement condition is correct, and paper white L* is slightly high (up to 1 unit higher), and b* is slightly bluer (up to 2 units lower) than the target paper white; this can be corrected with a little bit of yellow paper tint. Yellow dots will lower the L* value of the paper slightly and are not visible to the eye. It is not recommended to tint the paper with any other color ink.
If the color gamut is not large enough, you might want try a higher Total Ink Limit value. (see below).
Did I choose the right Printer Resolution?
For best image quality and color consistency you should use a resolution of 720x1440, or 1200x1200 or higher.
Did I choose the right spectrophotometer measurement condition?
Most modern spectrophotometers support 3 different measurement conditions: M0, M1, and M2.
M0 = default condition with an undefined amount of ultra-violet light in the color measurement illumination. (usually, a low amount of UV light)
M1 = high amount of ultra-violet light in the color measurement illumination (as defined by color standards).
M2 = no ultra-violet light in the color measurement illumination.
CIEL*a*b* values of the paper can be shifted by measurement condition of the spectrophotometer if there are fluorescent brighteners in the paper.
| Measurement Condition | Media Fluorescent Brightener (OBA) Level | L* | a* | b* |
|---|---|---|---|---|
M0 | High | Value is higher (1 or 2 units) | Usually not effected | Value is slightly negative (bluer) by up to 2 units |
Medium | Value is slightly higher (less than 1) | Usually not effected | Value is slightly negative (bluer) by up to 1 unit | |
Low | Usually not effected | Usually not effected | Usually not effected | |
M1 | High | Value is higher (1 or 2 units) | Usually not effected | Value is negative (bluer) by up to 4 units |
Medium | Value is less high (1 or less) | Usually not effected | Value is less negative (bluer) by up to 2 units | |
Low | Value is slightly higher (less than 1) | Usually not effected | Value is slightly negative (bluer) by up to 1 unit | |
M2 | High | Usually not effected | Usually not effected | Usually not effected |
Medium | Usually not effected | Usually not effected | Usually not effected | |
Low | Usually not effected | Usually not effected | Usually not effected |
Did I choose the right Total Ink Limit Value?
The color gamut should be large enough to meet the needs of your intended use of this media configuration. If the gamut is too small you can try printing the Total Ink Limit charts and increasing the total ink limit value by 0.1 or 0.2 units; check the chart with a loupe for artifacts at these levels.