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Author Topic: luminance level for Apple Cinema display  (Read 3721 times)
briphoto
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« on: January 21, 2009, 01:18:40 PM »
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Hello,
I was wondering if there is a luminance setting that might be too low for an Apple Cinema 20" display. I seem to recall reading somewhere that too low a setting can have an adverse effects on the video card. I'm having trouble getting a good monitor to print match, prints appear darker. I'm using coloreyes pro with the dtp puck setting luminance to 110. My printviewing setup is a solux clamp on fixture using the 50 watt 4700k bulb about 2 feet from the print. Is it better to increase the light falling on the print or decrease my monitor luminance? Does decreasing monitor luminance have an adverse affect on color accuracy? I work in a room with low ambient lighting.
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jackbingham
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« Reply #1 on: January 22, 2009, 08:03:49 PM »
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My first question would be, you asked for 110 but if you look in current system profile is that the value you actually hit?
The suggestion about lower luminances had nothing to do with damaging video cards. The issue is whether you can drop the luminance of an lcd below a certain level and still get good stable results. We're not talking damage here, we're talking stability and accuracy. That will depend on your particular monitor and what it will produce.
But first lets confirm that you are actually hitting your target.
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Jack Bingham
Integrated Color Corp Makers of Coloreyes Display
Wayne Fox
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« Reply #2 on: January 23, 2009, 07:45:41 AM »
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Quote from: jackbingham
My first question would be, you asked for 110 but if you look in current system profile is that the value you actually hit?
The suggestion about lower luminances had nothing to do with damaging video cards. The issue is whether you can drop the luminance of an lcd below a certain level and still get good stable results. We're not talking damage here, we're talking stability and accuracy. That will depend on your particular monitor and what it will produce.
But first lets confirm that you are actually hitting your target.

Seems if the OP used a calibration device to actually read the brightness  of the display, and modified the brightness so that shows a value of 110 (using a good software tool), it's pretty confirmed the target luminance is being achieved.

I'm not sure where you can confirm this looking in a system profile .. the computer doesn't know how much light the monitor is delivering, only what % of the maximum light is being delivered.

As to the question which is better, to increase the light hitting the print, or decrease the brightness of the display, it seems if you dim your display too far, it may get challenging to use.  Not because of stability ... just not enough light coming out for your eyes.  I don't think turning down the backlight has any adverse impact on stability ... it may make it better.

If your viewing station has adjustable brightness, then certainly setting up a luminance target, and adjusting the brightness of the viewing station to match the monitor should work well.  The goal here isn't just to have a particular "luminance" .. it's to try and get a similar "white" from the screen as compared to an unprinted piece of paper in your viewing station.

If you can't adjust the brightness of the viewing station (which is more common I believe), then luminance values are pretty irrelevant .. your only choice is to adjust the brightness of the monitor to match the viewing conditions.

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digitaldog
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« Reply #3 on: January 23, 2009, 09:20:39 AM »
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There is a minimum luminance a display can hit physically, after which I suspect going lower can only be accomplished by altering the LUT which is something we want to avoid if possible.

When I got my NEC 2690, I was told that going much below 140cd/m2 was going to be difficult to produce physically (altering the backlight) so I just adjusted my GTI boot up (even now, its only at 50%).

So, move one up, the other down, whatever produces a good match but understanding that each has limitations in either direction.
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Andrew Rodney
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briphoto
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« Reply #4 on: January 23, 2009, 10:41:09 AM »
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Thanks for the respones, anyone know at what luminance level the LUT  is altered? I'll probably stop at 90 and adjust the viewing area to achieve my best match.
Thanks,
Brian
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jackbingham
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« Reply #5 on: January 23, 2009, 06:18:55 PM »
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Seems if the OP used a calibration device to actually read the brightness  of the display, and modified the brightness so that shows a value of 110 (using a good software tool), it's pretty confirmed the target luminance is being achieved.

I'm not sure where you can confirm this looking in a system profile .. the computer doesn't know how much light the monitor is delivering, only what % of the maximum light is being delivered.

I asked him to look at Current System Profile, a dialog within ColorEyes that confirms the final luminance value. One should never assume that just because you asked for 120, that you will actually get it particularly when we are talking about an apple monitor. If the user selected the apple monitor plugin and the value he chose is dimmer than can be achieved using the monitor slider control than the target and the result will indeed not match. Monitors will not always be able to hit the targets we select for a host of reasons. Having tools to confirm final values and or point to issues that may indicate why not are critical to diagnosing issues.
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Jack Bingham
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« Reply #6 on: January 23, 2009, 06:21:47 PM »
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Quote from: briphoto
Thanks for the respones, anyone know at what luminance level the LUT  is altered? I'll probably stop at 90 and adjust the viewing area to achieve my best match.
Thanks,
Brian
This depends on what settings you choose. If you use the apple monitor plugin and you can hit your luminance target, colors will be adjusted in the video card but not luminance to any significant amount. If you choose LCD Brightness only, all adjustments will be made in the card, but again the amount depends on the difference between your target and the slider setting/brightness of your display, you settle on.
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Jack Bingham
Integrated Color Corp Makers of Coloreyes Display
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