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Calculating probe integration time

Author aprilliasky
#1 | Posted: 30 Apr 2013 08:45 
Sorry I was never good in maths. I read all the Lightspace manuals, and here is my problem:

I was trying to calculate the integration time with the method described in the CMS manual.

I did a little research on PDM. Used wikipedia. As I understand PDM is a value in kHz. My plasma display is able to monitor the horizontal and vertical frequency depending on the input signal. At 25fps the horizontal frequency is 28.13 kHz the vertical 25 Hz.

What confuses me, that in the given example integration time ("500*1/180 = 2.78 seconds") is calculated with 180Hz and not Khz which would be 0,18kHz.

Also I don't understand why any large integer value is good for the multiplication? Shouldn't it be a specific value?

I looked up my plasmas manual where in the frequency values were the same as stated by the plasma. I could not find any other datas for PDM.

I'm sure, there is something I don't understand. Can someone help please?

Also, is there any method for selecting extra delay time or the longer the better?


Author Steve

#2 | Posted: 30 Apr 2013 09:21 
PDM is the 'flicker time' of the plasma display cells - only your display manufacturer can tell you that.
This is a far higher value that the video frame rate.

The large 'integer value' is to get a 'sensible' integration time, based on the PDM value - the ratio of the PDM to the integration time is what really matters.

Hope this helps.

Steve Shaw
Mob Boss at Light Illusion

Author aprilliasky
#3 | Posted: 8 May 2013 06:45 
Someone has got a Panasonic TH-42PF30 display here?
I asked the Pana distributor several times, but can't get an answer on the PDM frequency and I need to calibrate my display.

Author Harry
#4 | Posted: 8 May 2013 10:18 
If you can't get the PDM information, I would try a multiple of the common refresh rate, e.g. if 50Hz refresh, than 100Hz or 200Hz
For 100Hz than I would set the integration time at 1s (100 x 0,01ms) or 2s (200 x 0,01ms)
Or for 200Hz = 0,5s or 1s or 1,5s

In any case the probe sould have a stable measurement at (e.g.) all grayscale levels.

Author aprilliasky
#5 | Posted: 8 May 2013 14:00 
As always, thank you Steve!
As I'm getting better with the calibration process I realize that a 5-10x times more expensive professional display is still better, than a cheap solution. It just saves your time, saves your money. So you can focus on the job.

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 Calculating probe integration time


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