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Color Management/WorkFlow > Hardware and Software > ColorVision PreCal/OptiCal Q's?

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AuthorSubject: ColorVision PreCal/OptiCal Q's?   [Go to Bottom of Page]
John MacLean
Posted on Wed Oct 8, 2003 5:28 PM

I sent the following to CV in an attempt to get a snappy answer to a stupid question, but I'm left wondering if there's an easier way. Sorry for all of the length, but here's our dialog:

----

Hello Ross,

Here is my question. Your User Guide.pdf mentions for CRT in "Standard Mode" to leave the monitor's brightness and contrast alone after using PreCal, but in "Precision Mode" it mentions to alter those settings.

Is this correct?

Thanks,
John

from User Guide.pdf:

Calibrating in Standard Mode
a) If you calibrated using PreCAL first, then click “Continue” through
the first two windows, as you already adjusted the contrast and
brightness in PreCAL. If you did not run PreCAL first, set the
monitor’s Contrast control to its maximum and the monitor’s
Brightness control to its minimum. Click “Next.”
b) Increase the monitor’s Brightness control until you barely see the
line in the center of the logo. Click “Continue.”
c) Attach the Spyder onto the screen so that it covers the picture of
the Spyder in the window. Click “Continue.”
d) The Spyder will then take readings.
10
e) When the small OptiCAL window appears, you may remove the
Spyder off of the screen.
f) Click “OK” to the Profile Name Window. On Windows, if you decide
to change the name of the profile, make sure that your name does
not include slashes, backslashes, colons, asterisks, question
marks, double quotes, less than symbols, greater than symbols or
vertical bars.
g) Click “OK” three times.

Calibrating in Precision Mode
a) Attach the Spyder onto the screen so that it covers the picture of
the Spyder in the window. Click “Continue.”
b) Adjust the monitor’s Brightness control until the current value meets
the target value as close as possible. Please remember to wait 15
seconds so that the Spyder can read the changes after the onscreen
controls disappear before you adjust the settings again.
Ensure there is no ambient room light directly striking the screen.
When the measurement is acceptable, click “Continue.”
c) The Spyder will now read samples.
d) Adjust the monitor’s Contrast control so that the current value
meets the target value as close as possible. Please remember to
wait 15 seconds so that the Spyder can read the changes after the
on-screen controls disappear before you adjust the settings again.
When the measurement is acceptable, click “Continue.”
e) The Spyder will now read samples.
f) When the smaller OptiCAL window appears, remove the Spyder
from the screen.
g) Either keep the existing profile name or change it to a custom one.
On Windows, make sure that your name does not include slashes,
backslashes, colons, asterisks, question marks, double quotes, less
than symbols, greater than symbols or vertical bars.
h) Click “OK” three times.

----

Hi John,

Yes, this is correct, but the user guide does not explain this process well enough. In 'Precision Mode' you are calibrating to a specific Black Luminance value (brightness), and a specific White Luminance value (contrast), as you can see in the main OptiCAL window. In 'Standard Mode' this option is grayed out and you are asked to determine these luminance values for yourself. 

The correct procedure for using 'Precision Mode' is below. Before beginning a Precision Mode calibration, you should first do a Standard Calibration. In brief you should do PreCal once a month, and either a 'Standard' or a combination of Standard/Precision Calibration, every two weeks.  

'Precision Mode Calibration'

Precision Mode provides a calibration process whereby the Black and White luminance levels can be set numerically based on measurements taken by the Spyder instrument. This is different from Standard Mode where White Luminance is simply maximized and Black Luminance is set using a visual target. When calibrating in Precision Mode the user specifies Black Luminance and White Luminance target values in addition to the regular Curve and Color Temperature target values. While OptiCAL does enter default values into the target Black Luminance and White Luminance fields these values are merely reasonable values for average monitors and viewing conditions. The user is responsible for choosing the Luminance values that are appropriate for their work.

If the user is calibrating to a published standard that includes Luminance values in addition to Gamma and Whitepoint specifications then those Luminance values should be used. Perhaps the user is calibrating a number of monitors in a workgroup in which case they want to use the same Curve, Whitepoint, Black Luminance and White Luminance target values for all of those monitors.

If the user does not know what Black Luminance and White Luminance target values they want to specify then the following procedure can be used to determine these values:

1) perform a calibration using Standard Mode

1a) set Brightness and Contrast controls as directed

2) perform a calibration using Precision Mode

2a) DO NOT CHANGE THE BRIGHTNESS OR CONTRAST CONTROL

2b) in the Adjust Black Luminance step write down the 'current' value

2b) in the Adjust White Luminance step write down the 'current' value

3) choose "Save Target As..." from the File menu

4) click Yes to include Luminance values in the Target file

5) enter the Black and White Luminance values that were recorded in step 2

5) after the Luminance values have been entered click Continue

6) specify a name for the new Target file and click Save

7) note that this new Target file is now the current Curve selection

When you re-calibrate always make sure that the Target file you created is selected in the Target Curve pop-up menu in the main OptiCAL window. Now you will now have the optimal Luminance value settings for your monitor.

Thank You,
Ross Hendricks
ColorVision Sales & Support
800-554-8688 phone
609-895-7447 fax
sales@colorvision.com
http://www.colorvision.com/


... this thread contains expert advice from Andrew Rodney.




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