NEC SpectraView 2190 User Manual page 42

 | SPECTRAVIEW II - USER'S GUIDE
Question: Each time I calibrate my monitor I receive a different Delta-E result. Should I recalibrate again if I receive
a value that is high?
Answer: For Delta-E values of less than 2 there is almost certainly no need to recalibrate. For values higher than 3
it is important to understand what the cause is, and if it is significant.
The calibration and adjustment process has inherent variability due to many factors such as the repeatability of
color sensor measurements, and changes within the display as it is adjusted. The basic accuracy and repeatability
specifications for most sensors is typically +/- 0.002 or higher for CIE xy, and +/- 2% for luminance. These variances
alone can give rise to Delta-E values of up to 2 or 3.
When a specific Intensity value is being used for the calibration, the Delta-E value is comprised of the luminance
and color differences. Differences in color are much more critical than a difference in relative luminance. Look at the
results of the calibration shown in the Information window to determine if the high Delta-E value is caused mainly
by a shift in color or in luminance.
High Delta-E values can also occur if a specific Intensity value is being used for the calibration and the display is
not capable of achieving the specified Intensity value. The calibration will always aim to achieve the specified White
Point, even if the Intensity value could not be reached. If the display can not be calibrated to achieve the specified
Intensity value modify the value accordingly.
In some situations, the display Intensity will drift slightly for several minutes after it is adjusted. Since the measured
value used to calculate the final Delta-E result is taken up to one or two minutes after the display was adjusted,
a higher Delta-E value may be shown, even though the calibration process achieved the specified Target values
during the calibration process. Selecting the Extended luminance stabilization time option in the Preferences can
be used to try and minimize this effect.
Question: The Delta-E result values shown in SpectraView are higher than those shown in other display calibration
applications. Does that mean they are better at calibrating the display than SpectraView?
Answer: No. SpectraView calculates the Delta-E values using both the luminance and color differences for more
realistic and accurate values. Other applications may calculate Delta-E differently.
Question: After calibration I manually adjusted some of the monitor controls to get a better color match for my
particular application. What happens the next time I calibrate the monitor?
Answer: The manual adjustments will be reset by the calibration process.
In general it is not a good idea to manually adjust the monitor after calibration because it not only invalidates the
calibration and ICC/ColorSync profile, but also means that the adjustments will be lost the next time the monitor is
calibrated.
If you still feel it is necessary to tweak the display after calibration, a much better approach is to create a new Target
file based from the measurements of the display after it has been manually adjusted. That way the monitor will be
automatically calibrated to that particular set of characteristics the next time it is calibrated. Use the Custom White
Point tool to measure and set the white point and Intensity values.