CCFL LCD "warmup" time - Page 2 - AVS Forum
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post #31 of 40 Old 05-14-2012, 02:14 PM - Thread Starter
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Originally Posted by Phase700B View Post

Guess no one really cares?

Dead end thread??

Last time I "fall" for this. . . lol.

Not at all!

Thanks for taking the time to do this. I should have time late this evening to record and post my readings at the time intervals you used.

Been really busy...
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post #32 of 40 Old 05-14-2012, 04:52 PM
 
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Originally Posted by djams View Post

Not at all!

Thanks for taking the time to do this. I should have time late this evening to record and post my readings at the time intervals you used.

Been really busy...

I figured you'd be right along pretty soon.

Just had to give an 'ol Michigander a little tweak. I actually took two sets of readings to verify. The first was Saturday night for 4 hours and then Sunday morning for 3 hours to see if I got the same results. . . . which I did. Worked out ok as we watched some programs on the Mits while I monitored and recorded the LG findings.
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post #33 of 40 Old 05-15-2012, 08:53 AM - Thread Starter
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Originally Posted by Phase700B View Post

Output after specified time:

100 lux @ 3 min. 37%
193 lux @ 15 min 71%
235 lux @ 30 min 87%
251 lux @ 45 min 92%
261 lux @ 60 min 96%
267 lux @ 90 min 98.8%
270 lux @ 105 min 100%

BTW. . . what are your figures for similar times? I know you said 2 hours to peak output I think.

Well, here are my numbers. As you can see, my set basically behaved like a champ for this test. Not at all like the behavior I saw last week. There is an unknown for these readings. I do not know how long the set had been powered off. I got home very late from work and my wife was in bed. So I will try this again when I know the set is completely "cold".

These readings were obtained using my i1d2, unit is nits. The max output stabilized at 125-ish. I monitored it for 2 hours total. I checked my recent calibration, and the final verification runs showed 127 nits, so after 2 hours it got very close to where it was after ~5 hours.

71.94 @ 3 min (58%)
95.86 @ 15 min (77%)
112.1 @ 30 min (90%)
118.9 @ 45 min (95%)
122.5 @ 60 min (98%)
124.6 @ 90 min (100%)
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post #34 of 40 Old 05-15-2012, 01:57 PM
 
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Originally Posted by djams View Post

Well, here are my numbers. As you can see, my set basically behaved like a champ for this test. Not at all like the behavior I saw last week. There is an unknown for these readings. I do not know how long the set had been powered off. I got home very late from work and my wife was in bed. So I will try this again when I know the set is completely "cold".

These readings were obtained using my i1d2, unit is nits. The max output stabilized at 125-ish. I monitored it for 2 hours total. I checked my recent calibration, and the final verification runs showed 127 nits, so after 2 hours it got very close to where it was after ~5 hours.

71.94 @ 3 min (58%)
95.86 @ 15 min (77%)
112.1 @ 30 min (90%)
118.9 @ 45 min (95%)
122.5 @ 60 min (98%)
124.6 @ 90 min (100%)


Well, numbers look ok if not better than mine with 3,000 hours on it. I know both my readings on Sat night and Sun morning were with a cold TV off for at least 10 hours or more each time. Looks like max output from about 90% up is about the same time. Seems are TVs are aging about the same. I am still very satisfied with my 5.4 year old Mitusbishi LCD as well for max brightness , but I have no idea how many hours on it. . . double the LG I would guess or more since the wife leaves it on a lot!

I'll have to make a ramp up run on the Mits soon and see how it compares.

BTW, I tried converting the lux readings to nits according to charts and formulas I found on the net. Somehow they don't seem to match my old D2 readings in nits. The 1330B fc/lux meter I used for these current readings is very sensitive and stable and several AVS members use it for their projector screens and lamps.
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post #35 of 40 Old 05-16-2012, 10:52 AM - Thread Starter
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Originally Posted by Phase700B View Post

BTW, I tried converting the lux readings to nits according to charts and formulas I found on the net. Somehow they don't seem to match my old D2 readings in nits. The 1330B fc/lux meter I used for these current readings is very sensitive and stable and several AVS members use it for their projector screens and lamps.

I made an effort at converting these as well. My first stop was WolframAlpha, which states that "lux and nits are incomptible".
http://www.wolframalpha.com/input/?i...rt+lux+to+nits

I then found 2 more luminance conversion sites where it is not possible to convert between the two units.
http://www.unitconversion.org/unit_c...inance-ex.html
http://www.sooeet.com/light/lux.php

It seems the problem is that lux is a measurement of illuminance, while nits is luminance. I found this simple explanation if the difference, which explains why, for a projector setup, lux could be used to measure the bulbs and nits would be used to measure on the screen. However, it confuses me why we use nits or fL to measure a display that emits a light source. Seems like it should be lux, technically. *shrug*

At any rate, I think the % changes measured using either unit are valid.
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post #36 of 40 Old 05-16-2012, 02:16 PM
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Quote:
Originally Posted by djams View Post

I made an effort at converting these as well. My first stop was WolframAlpha, which states that "lux and nits are incomptible".
http://www.wolframalpha.com/input/?i...rt+lux+to+nits

I then found 2 more luminance conversion sites where it is not possible to convert between the two units.
http://www.unitconversion.org/unit_c...inance-ex.html
http://www.sooeet.com/light/lux.php

It seems the problem is that lux is a measurement of illuminance, while nits is luminance. I found this simple explanation if the difference, which explains why, for a projector setup, lux could be used to measure the bulbs and nits would be used to measure on the screen. However, it confuses me why we use nits or fL to measure a display that emits a light source. Seems like it should be lux, technically. *shrug*

At any rate, I think the % changes measured using either unit are valid.

"Luminance vs. Illuminance

You obtain these figures somewhat differently depending upon whether you have a direct view/flat panel/rear projection display or a front projector. For direct view/flat panel/rear projection displays, just attach the probe to the screen and measure directly. The software will measure either in imperial fL (foot-lamberts) or in metric cd/m2 (candelas per meter squared or nits). If you measure in nits, just multiply the output by 0.292 to get fL. If you measure in fL, then multiply by 3.426 to get nits. Nits and fL are both a measure of luminance, which is an emission or reflection of light from a flat, diffuse surface. All colorimeters and spectroradiometers natively measure luminance.

If you have a front projector, it is a little more complicated. First, a good illuminance meter is useful for this. Illuminance is a measurement of light that falls on or illuminates surfaces. Thus, while reading light off the screen would be a luminance measurement in nits or fL, measuring light directly from the projector's lamp would be an illuminance reading in Lux. Front projectors are about 1/3 the brightness of a typical flat panel, thus the black level measured off the screen is very low. Unless you have an expensive luminance meter, such as the Konica Minolta LS-100 which can accurately measure very low luminance, you may get more accurate readings by taking an illuminance reading directly from the lamp. The AEMC meter cited at the beginning of this tutorial is a good choice.

Just place the meter against the screen facing the projector's lamp and read a 100% output pattern in Lux. Then divide the Lux by 10.76 and multiply by the real* gain of the screen to get the fL for the projector. To get the lumens of the projector's lamp, just multiply the lux by the screen area in square feet and then divide by 10.76.

* Note: a screen's real gain will often be lower than its advertised gain. Manufacturers routinely inflate a screen's gain rating. Stewart is the only company I know of whose gain ratings are reasonably accurate."

from: http://www.avsforum.com/avs-vb/showp...98&postcount=1
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post #37 of 40 Old 05-16-2012, 07:00 PM - Thread Starter
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That's pertinent, thanks

So in the case of Nick's lux readings, how would he determine the "gain" of his LCD screen in order to use the conversion calculation described above?
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post #38 of 40 Old 05-16-2012, 08:37 PM
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Quote:
Originally Posted by djams View Post

That's pertinent, thanks

So in the case of Nick's lux readings, how would he determine the "gain" of his LCD screen in order to use the conversion calculation described above?

that's only for FP setups; you'd need a light meter that reads in fL or cd/m^2 for direct view displays like LCD Flat-Panels
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post #39 of 40 Old 05-17-2012, 05:40 AM
 
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Quote:
Originally Posted by djams View Post

I made an effort at converting these as well. My first stop was WolframAlpha, which states that "lux and nits are incomptible".
http://www.wolframalpha.com/input/?i...rt+lux+to+nits

I then found 2 more luminance conversion sites where it is not possible to convert between the two units.
http://www.unitconversion.org/unit_c...inance-ex.html
http://www.sooeet.com/light/lux.php

It seems the problem is that lux is a measurement of illuminance, while nits is luminance. I found this simple explanation if the difference, which explains why, for a projector setup, lux could be used to measure the bulbs and nits would be used to measure on the screen. However, it confuses me why we use nits or fL to measure a display that emits a light source. Seems like it should be lux, technically. *shrug*

At any rate, I think the % changes measured using either unit are valid.

Yes, I ran into the same seemingly contradictory information. While illuminace is one thing and luminance is another. . . one is basically reflected light and the other source light. However, electronically, the sensor used to measure them is the same type of photo diode. The only difference is in what the meter is set up to DO with the output of the photo diode sensor.

So, yes, I also agree you it seems the measurement units are related, they
are not directly converted. "Gain" is not something that is relevant to an emissive LCD panel. . only a reflective projection screen. The units are actually irrelevant in this case and the rise measured in lux would still be the same if measured with a meter that uses fl, lumens, etc.

A lux meter is usually used to measure the amount of light in rooms for technical purposes such as office lighting, minimum levels in various room locations etc. So , technically, it IS reading source light . . . but from a distance and how much in a given area. So I guess I could put the meter 6 feet way from the screen in a completely dark room and see if I get a similar light output rise. But there is less chance of ambient light "leaking" around the edge of the photo diode sensor by placing it right on the LCD screen. You only need a meter that reads in fl or candelas per square meter if you are actually interested in the actual amount of emitted light. In the case of light output rise all we need is a a relative starting and ending point. You could even take a simple digital volt meter and connect a photo diode to it placed on the screen of the LCD panel and read the starting and ending values in volts. The percentages would be the same. All a light meter does it determine what units the voltage output of the photo diode is going to display.
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post #40 of 40 Old 05-17-2012, 08:18 AM
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@djams - nice to see you actively posting again with good, OT, info. Makes me wish I had a meter so I could apply what I'm learning

@Phase - hiya!
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