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Measuring the White Point

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Clayton Burkhart
Measuring the White Point
on Jun 6, 2011 at 8:00:07 am

Hello,
Having a bit of difficulty understanding how to measure the luminance of my 1770 (used in conjunction with a Matrox MXO out from an iMac through HD-SDI). As it is advised to do this to adjust for eventual luminance changes over time I wanted to stay on top of this.

It's not clear to me how to actually ONLY measure the white point or luminance as opposed to actually doing a calibration. It has been my experience that this info is only provided once a calibration has been done. Obviously I do not want to do that. This is also complicated by the fact that I would be measuring a 2nd monitor which is setup for YUV through HD-SDI to boot.

I have a Colorspyder puck and use Coloreyes Display Pro software.

Any help in figuring out how to do this would be appreciated.


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Bram Desmet
Re: Measuring the White Point
on Jun 6, 2011 at 11:50:27 am

Hi Clayton,

Most software will allow you to take a manual measurement that will generate x,y (chromaticity) and Y (luminance) readings. You would want to generate a 100 percent white filed from either an editing system or test signal generator and then use this software to take a reading and record the luminance value. How you generate the test pattern is not as important as making sure you can generate the identical test pattern in the future.

The chromaticity values will not be particularly reliable and in our testing many puck style colorimeters actually drift more significantly than the monitor they are measuring, especially with respect to chromaticity readings. However, luminance readings at 100 percent white tend to be a bit more accurate from such inexpensive probes and regardless of the actual accuracy of these luminance readings what we have found is that the luminance readings do at least seem to stay relatively consistent (so whatever error in luminance reading there is at least stays essentially the same). This means you can typically use such probes to read a luminance value at 100 percent white and then maintain this value with the backlight setting over time as overall luminance is the main area of anticipated drift on the monitor over time.

If you have more questions about this please contact us at support@flandersscientific.com or 678.835.4934

Bram Desmet
FSI (Flanders Scientific, Inc.)
http://www.FlandersScientific.com


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