Video Calibration

CalMAN Video Display Analysis System


Charts and Measurement Examples

CalMAN has over 50 charts available to measure every aspect of display performance.  I wanted to show a few images of the more commonly-used ones along with sample data from my various experiments.  The figure shown below illustrates the two most useful charts for measuring color performance.  On the left is a CIE gamut chart.  The squares show the reference color points for primaries and secondaries.  The dots show the measurement.  When a dot is fully inside a square, the Delta E* (color error) is under 3 which is invisible to the eye.  The luminance chart shows the colors brightness compared to the reference which is calculated by CalMAN automatically.  The goal is to have the colored bars even with the black ones.  If your display has a color management system, you would adjust the lightness or brightness controls for each color.



Here are some of my favorite charts for measuring grayscale and gamma.  The Delta E* bar graph shows the amount of deviation from 6500k at each stimulus level.  Anything under 3 is invisible to the eye.  A Delta E* of under 1 is superb performance.  The Point Gamma chart shows the gamma at each stimulus level.  This is much more useful than a single average gamma number because you can see potential problems at each point in the grayscale.  Displays with customizable gamma curves can be adjusted to create the flat gamma chart you see here.  The RGB Tracking chart shows the white balance at each stimulus level.  Here again it is very easy to see where a color needs to be raised or lowered to achieve the correct color temperature.


CalMAN Professional

Though this article is aimed at the do-it-yourself calibrator, I’d like to briefly describe the extra features available in the Professional version of CalMAN.

Firstly is CalMAN’s signal generator integration.  Pro calibrators always use a reference signal generator to calibrate a display.  Test discs are used at the end of a session to verify results and make small adjustments for a particular source component.  I use one of CalMAN’s supported generators, the Accupel HDG-3000.  I connect it to my laptop using a USB-Serial adapter to engage the Accupel’s RS-232 interface.  CalMAN has full control of the generator during the calibration session.  I can select patterns from a drop-down list if I wish.  I can also do an entire measurement run by simply pressing F10.  CalMAN displays the appropriate pattern, takes a measurement, records it on the chart and moves automatically to the next pattern and measurement.  By streamlining the process this way, it’s super-easy to profile a display.  I can use the multi-tab interface to compare different picture modes or color temp presets.  By taking more readings and comparing them this way, I have more time to address all the adjustment options offered by a TV.  The end result is a more thorough job where I’ve used every possible control to maximize a display’s potential.

The other major feature available in CalMAN Professional is custom report design.  Here you can literally create any set of charts you wish and arrange them any way you like.  I’ve created reports for grayscale and color data for example.  In one layout I can see all parameters like gamma, Delta E* (color error), and grayscale tracking.  You can resize the charts and zoom in on them if you want to change the scale or focus on specific areas.  Besides charts, you can also have the raw data in your reports.  I often like to see the specific numbers for a measurement.  You can have spreadsheet-style tables that contain any datasets you feel are pertinent.  The screen shots below show typical grayscale and color performance reports.



CalMAN Pro also includes a customer database which makes it easy to organize all your data and display information for each client.  Any chart from any layout can be copied to the clipboard and pasted into other Windows applications.  You can also save any screen to PDF format.

CalMAN’s user options are quite extensive.  You can define your own colorspace with the color target editor.  This allows you for instance, to calculate the correct positions of the secondary colors relative a display’s actual primaries rather than the reference ones.  You can enable a low-light trigger to force your meter to take and average multiple readings for greater accuracy.  You can also change the targets for parameters like colorspace, gamma, and Delta E*.  It is also possible to create meter profiles.  These enable you to “train” one meter to another.  This is a great way to compensate for the inaccuracies in a less-expensive instrument by using a more accurate one as a reference.