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Author Topic: Intensity vs Brightness NEC calibration  (Read 1729 times)

hokuahi

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Intensity vs Brightness NEC calibration
« on: October 21, 2017, 09:10:14 PM »

Using the bundled NEC SpectraView and software to calibrate my NEC PA302W I have the Intensity set at 80 cd/m2 to keep my prints from being too dark. The OSD and Multiprofiler app both show Brightness 137 cd/m2. My prints are still slightly dark and Iím wondering if lowering the Brightness to 120 cd/m2 will help.
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xpatUSA

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Re: Intensity vs Brightness NEC calibration
« Reply #1 on: November 24, 2017, 05:57:36 PM »

Using the bundled NEC SpectraView and software to calibrate my NEC PA302W I have the Intensity set at 80 cd/m2 to keep my prints from being too dark. The OSD and Multiprofiler app both show Brightness 137 cd/m2. My prints are still slightly dark and Iím wondering if lowering the Brightness to 120 cd/m2 will help.

May not help much but I just noe looked at my P242W brightness setting. It was 38% - a peculiar number because the screen is pretty bright but, ho hum.

Then I made a fully white image in FastStone. Applying my +/- 5% lux-meter to the screen it told me 170lx - about right for what I see.

So, for myself, I would trust my lux-meter over over a "brightness" setting which can often mean anything.

regards,

Ted

P.S. I know 170lx might be considered by some to be "too bright", but a) I don't print and b) my old eyes are quite dim.
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best regards,

Ted

Doug Gray

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Re: Intensity vs Brightness NEC calibration
« Reply #2 on: November 24, 2017, 07:28:51 PM »

May not help much but I just noe looked at my P242W brightness setting. It was 38% - a peculiar number because the screen is pretty bright but, ho hum.
That indicates your monitor's current white point is 38% of its max. If you set the cd/m^2 at 120 then that indicates your monitor could be set as bright as just under 300 cd/m^2

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Then I made a fully white image in FastStone. Applying my +/- 5% lux-meter to the screen it told me 170lx - about right for what I see.

So, for myself, I would trust my lux-meter over over a "brightness" setting which can often mean anything.
I wouldn't.  A Lux meter measures illuminance and integrates light from all angles of a plane. A monitor's luminance drops off once the angle shifts from head on. If you look at the monitor even at 20 degrees from the monitor's plane it will likely appear much dimmer. As a result, there is no practical way to measure monitor luminance with a Lux meter no matter how accurate the meter.

A Lux meter measures incident light or illuminance. Monitor screens are measured in luminance, usually as cd/m^2.  500 Lux when illuminating a very white paper, WP of L*98, like a good Baryta, results in a luminance slightly reduced from 500/Pi or around 160 cd/m^2.
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xpatUSA

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Re: Intensity vs Brightness NEC calibration
« Reply #3 on: November 24, 2017, 10:13:32 PM »


That indicates your monitor's current white point is 38% of its max. If you set the cd/m^2 at 120 then that indicates your monitor could be set as bright as just under 300 cd/m^2

Sorry to the OP and your goodself. I was in so much of a rush to help, I completely forgot 'Lighting 101'!

Yes, my monitor is 350 cd/m^2 max and 38% of that is 133 cd/m^2. Good estimate on your part.

Quote
A Lux meter measures illuminance and integrates light from all angles of a plane. A monitor's luminance drops off once the angle shifts from head on. If you look at the monitor even at 20 degrees from the monitor's plane it will likely appear much dimmer. As a result, there is no practical way to measure monitor luminance with a Lux meter no matter how accurate the meter.

A Lux meter measures incident light or illuminance. Monitor screens are measured in luminance, usually as cd/m^2.  500 Lux when illuminating a very white paper, WP of L*98, like a good Baryta, results in a luminance slightly reduced from 500/Pi or around 160 cd/m^2.

The sad part is that I knew most of the the above apart from the paper details. I'm old . . what I knew a few weeks ago, when testing ISO on some of my cameras, today has gone away. :(

Thanks for the correction!

Ted
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best regards,

Ted

Doug Gray

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Re: Intensity vs Brightness NEC calibration
« Reply #4 on: November 24, 2017, 10:52:22 PM »

Sorry to the OP and your goodself. I was in so much of a rush to help, I completely forgot 'Lighting 101'!

Yes, my monitor is 350 cd/m^2 max and 38% of that is 133 cd/m^2. Good estimate on your part.

The sad part is that I knew most of the the above apart from the paper details. I'm old . . what I knew a few weeks ago, when testing ISO on some of my cameras, today has gone away. :(

Thanks for the correction!

Ted

Ted, no problem. But getting back to the OP's issue of a very large difference between his cd/m^2 here's what I do with a good lux meter.

1. Get a good unprinted matte paper. Assume WP  L* is around 95 to 97
 
2. Position it from a lamp so that the Lux level at the surface is approx. 1.1*3.14 the monitor's presumed cd/m^2

3. Now the monitor's white should be the same luminance as the paper from the lamp.  If not, adjust the lamp distance so that they match.

4 Then read the Lux level at the paper's surface and reverse the calculations. For instance if the Lux level is 350 then the monitor's Luminance, when matching, would be about LuxReading/(3.14*1.1) or around 110 cd/m^2
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Czornyj

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Re: Intensity vs Brightness NEC calibration
« Reply #5 on: November 25, 2017, 07:02:51 AM »

Using the bundled NEC SpectraView and software to calibrate my NEC PA302W I have the Intensity set at 80 cd/m2 to keep my prints from being too dark. The OSD and Multiprofiler app both show Brightness 137 cd/m2. My prints are still slightly dark and Iím wondering if lowering the Brightness to 120 cd/m2 will help.

This may indicate that the sensor is of poor quality or broken. What model did you use?

hokuahi

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Re: Intensity vs Brightness NEC calibration
« Reply #6 on: November 25, 2017, 09:46:54 AM »

The sensor is the one that came with the monitor, "NEC MDSVSENSOR3 Custom Calibrated for Wide-Gamut NEC Displays Powered by x-rite".
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xpatUSA

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Re: Intensity vs Brightness NEC calibration
« Reply #7 on: November 25, 2017, 10:01:33 AM »

Ted, no problem. But getting back to the OP's issue of a very large difference between his cd/m^2 here's what I do with a good lux meter.

1. Get a good unprinted matte paper. Assume WP  L* is around 95 to 97
 
2. Position it from a lamp so that the Lux level at the surface is approx. 1.1*3.14 the monitor's presumed cd/m^2

3. Now the monitor's white should be the same luminance as the paper from the lamp.  If not, adjust the lamp distance so that they match.

4 Then read the Lux level at the paper's surface and reverse the calculations. For instance if the Lux level is 350 then the monitor's Luminance, when matching, would be about LuxReading/(3.14*1.1) or around 110 cd/m^2

Looks good enough for your purpose, Doug.

For mine (measuring a camera ISO) , I was fortunate to have some Kodak R27 white/gray 8x10 cards, so no need for me to guess the 'R' value.
« Last Edit: November 26, 2017, 03:55:01 PM by xpatUSA »
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best regards,

Ted
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