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Epson presented an interesting demo at CES this year. It involved a relatively new video-measurement standard adopted by SID (Society for Information Display) called color light output (CLO). Most of us are familiar with white light output (WLO), more commonly called peak white level. And of course, white is simply a mixture of red, green, and blue, so if you were to measure the maximum level of the three primaries and add them together—which yields the CLO—you should get the same value as the peak white level.

 

However, this is not always the case. In particular, single-chip DLP projectors sometimes include a white (clear) segment in the color filter wheel to increase the peak white level, and some filter wheels also include segments with one or more of the secondary colors (yellow, cyan, magenta). Therefore, when you add the maximum levels of red, green, and blue, the result is lower than the measured peak white level, because those extra segments are not used in the RGB measurements, whereas they are used in the white measurement.

 

The effect of CLO was clearly evident in the side-by-side demo shown in the photo above. Two 720p projectors with the same rated WLO were fed the same signal from one Blu-ray player using an HDMI splitter, and each projector was set to its brightest out-of-the-box mode with no other tweaking. They were firing onto identical screens (Screen Innovations Lunar Gray, 16:10, 120 inches diagonal, 0.85 gain).

 

On the right is the image produced by an Epson 750HD, while the image on the left was produced by an Optoma GT750E. Both have a WLO rating of 3000 lumens, and measurements made in the venue were quite close to this value—2920 for the Epson, 2840 for the Optoma. However, the measured CLO was quite different—2950 for the Epson, 980 for the Optoma. As you can plainly see, the Epson's image is a lot brighter than the Optoma's, and the colors are not the same.

 

You might think the CLO measurement is designed to make the specs of LCD projectors look better than those of single-chip DLPs. But the measurement methodology was developed by SID, which has no skin in that game. Also, any 3-chip design, including LCD and LCoS as well as 3-chip DLP, is likely to have equal WLO and CLO. Finally, there are single-chip DLP projectors—those with only red, green, and blue segments in their color wheels—that have the same WLO and CLO measurements.

 

For more on this, visit www.colorlightoutput.com , where you will find lots of interesting info, including the results of independent third-party tests of many projectors. Those results include the manufacturers' WLO specs and independently measured CLO; I'd prefer to see independent measurements of both.
 

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Hey Scott, does this in anyway affect contrast?
 

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This information is extremely biased by these points:


1. No one (on AVS) runs an HT projector "wide open" for lumens as that hammers contrast and black level

2. No one (on AVS) runs a serious HT projector that puts out 3000 lumens (and probably 150:1 ansi contrast)

3. The CLO number is much less impressive if we're talking 500-800 lumens, which is a more usable output for HT (who uses a 120" 0.85 gain grey screen unless your have too many lumens and zero contrast?)

4. Measurements are meaningless, if a DLP color wheel is designed well enough to trick the human eye but it "measures badly", who cares?


Sorry, just another biased "research report" that proves only that someone is trying to sell ussomething.
 

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Discussion Starter · #4 ·

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Originally Posted by e39mofo  /t/1451895/epson-color-light-output-demo-at-ces-2013#post_22833506


Hey Scott, does this in anyway affect contrast?
I would think so, at least when viewing real program material. One could calculate "CLO contrast" by dividing the CLO by the black level; if the CLO is less than the WLO, the contrast would be lower than the peak-white contrast as well. I'll be talking about this subject on my podcast in February (tentatively 2/11) with a color scientist, and I'll be sure to ask this question.
 

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Originally Posted by pottscb  /t/1451895/epson-color-light-output-demo-at-ces-2013#post_22833562


This information is extremely biased by these points:


1. No one (on AVS) runs an HT projector "wide open" for lumens as that hammers contrast and black level

2. No one (on AVS) runs a serious HT projector that puts out 3000 lumens (and probably 150:1 ansi contrast)

3. The CLO number is much less impressive if we're talking 500-800 lumens, which is a more usable output for HT (who uses a 120" 0.85 gain grey screen unless your have too many lumens and zero contrast?)

4. Measurements are meaningless, if a DLP color wheel is designed well enough to trick the human eye but it "measures badly", who cares?


Sorry, just another biased "research report" that proves only that someone is trying to sell ussomething.
Of course, you are correct that, for home theater applications, a calibrated projector is not run "wide open" at 3000 lumens, and a serious HT enthusiast would not use such a screen as that used for this demo, which was intended only to demonstrate the delta between WLO and CLO. Even under ideal HT conditions, a significant delta between WLO and CLO means that real program material would exhibit less brightness and contrast than the peak-white level and contrast measurements would indicate (not to mention inaccurate colors). I disagree that measurements are meaningless, though they certainly do not tell the whole story. The bottom line is picture quality of real program material, but properly conducted measurements can reveal things that are worth knowing. And don't forget that this measurement standard comes from SID, whose only concern is picture quality.
 

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Hmm very interesting. Could be a handy spec to compare unless companies whore the spec out the way all companies do to contrast ratio. Scott its cool to see our posting here I talked to u many times over the years over at HT, under the screen name Jarod, and a big fan! What can I say I love HT geeks podcast. I never miss an episode. Maybe you could get a Dolby rep to come talk about Atmos and it's future?
 

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Quote:
Originally Posted by Scott Wilkinson  /t/1451895/epson-color-light-output-demo-at-ces-2013#post_22833666


Of course, you are correct that, for home theater applications, a calibrated projector is not run "wide open" at 3000 lumens, and a serious HT enthusiast would not use such a screen as that used for this demo, which was intended only to demonstrate the delta between WLO and CLO. Even under ideal HT conditions, a significant delta between WLO and CLO means that real program material would exhibit less brightness and contrast than the peak-white level and contrast measurements would indicate (not to mention inaccurate colors). I disagree that measurements are meaningless, though they certainly do not tell the whole story. The bottom line is picture quality of real program material, but properly conducted measurements can reveal things that are worth knowing. And don't forget that this measurement standard comes from SID, whose only concern is picture quality.

I don't know if it's relevent to this conversation but many, if not most home theater 3D projectors are ran wide open to suck out as much light output as possible to compensate. My Ben Q W7000 only runs 3D in high lamp with dynamic iris turned off and iris wide open. Most reviews of other ones ive seen seem to do the same. So is CLO relevent to 3D?
 

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Discussion Starter · #8 ·

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Originally Posted by Reddig  /t/1451895/epson-color-light-output-demo-at-ces-2013#post_22836841


Hmm very interesting. Could be a handy spec to compare unless companies whore the spec out the way all companies do to contrast ratio. Scott its cool to see our posting here I talked to u many times over the years over at HT, under the screen name Jarod, and a big fan! What can I say I love HT geeks podcast. I never miss an episode. Maybe you could get a Dolby rep to come talk about Atmos and it's future?
Hey Jarod/Reddig, thanks so much for the kind words! Glad to see you here! As it happens, my podcast guest on Jan. 28 is scheduled to be Dolby's Atmos guy, Ioan Allen.
 

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Discussion Starter · #9 ·

Quote:
Originally Posted by Reddig  /t/1451895/epson-color-light-output-demo-at-ces-2013#post_22836882



I don't know if it's relevent to this conversation but many, if not most home theater 3D projectors are ran wide open to suck out as much light output as possible to compensate. My Ben Q W7000 only runs 3D in high lamp with dynamic iris turned off and iris wide open. Most reviews of other ones ive seen seem to do the same. So is CLO relevent to 3D?
You are correct that in 3D mode, most projectors do run wide open because they need to pump out as much light as possible to combat the drastic light loss through 3D glasses, especially active glasses. My podcast guests on Feb. 11 are scheduled to be a couple of CLO experts, and I'll be sure to ask this question about CLO and 3D. Thanks!
 

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RGB Separation is a key measurement for any display, and a good Separation is required if a display is to accurately portray the images presented to it.


As a consequence I fail to see how this 'new' measurement standard is new?


It sounds to me like previous calibration checks have just not been performed correctly when comparing displays or projectors?


Steve
 

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Just the headline of this makes me a little crazy. I drove all the way from south of Tucson to Las Vegas to go to CES, and my primary reason for doing so was to visit Epson and see what they were up to. When I got there, I was shocked and dismayed that they were NOT LISTED in the official list of exhibitors! Where in the heck were they, Scott?
 

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Discussion Starter · #12 ·

Quote:
Originally Posted by Light Illusion  /t/1451895/epson-color-light-output-demo-at-ces-2013#post_22842535


RGB Separation is a key measurement for any display, and a good Separation is required if a display is to accurately portray the images presented to it.


As a consequence I fail to see how this 'new' measurement standard is new?


It sounds to me like previous calibration checks have just not been performed correctly when comparing displays or projectors?


Steve
Not sure I know what you mean by "RGB Separation" in this context; that is, as a measurement. Perhaps I know it by another name. Can you please elaborate? Thanks!
 

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While it is marketing, it sounds like the CLO number is a more truthful indicator of the capabilities of a projector than the WLO number is, so in that sense I think this is a useful measurement to have published for projectors. It reminds me of the CRI number of fluorescent light bulbs, which indicates the accuracy of the rendering of colors of objects when illuminated by such a bulb. Cheaper tubes typically have a lower CRI. It's useful to have that number published in case you care about it (think of art galleries or people who work with colors for a living). I used it to help decide which tubes to put in my home office for example.
 

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Quote:
You might think the CLO measurement is designed to make the specs of LCD projectors look better than those of single-chip DLPs. But the measurement methodology was developed by SID, which has no skin in that game.

Just adding fuel to the fire...


"3. The White Brightness data in Table 2 was obtained through Projector Central, as specified by the manufacturers. These manufacturers do not provide Color Brightness (Color Light

Output) data. Color Brightness was determined in compliance with IDMS 15.4 by 3rd party laboratory testing of a single unit of each model. Serial numbers available on request at
[email protected]"

http://www.colorlightoutput.com/assets/Color_Brightness_Buyers_Guide.pdf
 

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Because I work in visual simulation I am very happy to see the CLO spec and I hope it becomes widely adopted. We use a variety of projector products and technologies, including single chip DLP. When we do use a single chip DLP projector, we stipulate a color wheel without a white segment, sometimes called a "simulation" option. Providing CLO along with WTO is a welcome improvement in the spec game.


Do you know if the CIE color coordinates are also part of the information to be specified?
 

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This spec is an interesting development.


Many years ago (late 90's) when developing the color space specifications for digital cinema, we made saturated red, green, blue, magenta, cyan, yellow, and white patches on Kodak Vision film. We projected these and measured the chromaticity and luminance of each patch. We found that the luminance of R+G+B was considerably dimmer than the luminance of white (less than half). Of interest is that if one wishes to replicate colour dynamics of film on the digital projector, a projector with color lumens = white lumens will be throwing away bitdepth in the saturated primary colors. On the other hand, if the primary colors match the luminance of film (relative to peak white), the projector will use the full bitdepth to represent the colors. This of course implies that quality 3D color processing is enabled (which is available in the DLP projectors, through P7 color processing.) Our first color models for the digital cinema projectors enabled P7 processing and developed a profile where we depressed the luminance of RGB relative to the CYM and W primaries, and we were able to achieve much better and smoother replication of the film colour relationships.


Matt Cowan
 

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1) Most of us know the whole brightness measuring thing is a marketing tool, but it is useful - I prefer the screenshot of the Optoma on the left, but in a sunny room, the Epson's picture might be more viewable


2) While colour accuracy can be measured, ultimately it all depends on perception, not measurements.


The average between red and green peaky filters are interpreted by our brains as YELLOW when the projectors or displays are outputting a spread between red and green that might not even have the yellow wavelength, or might not have it as the brightest wavelength. The viewer's retina processes the intensities, and our brain fills in the gaps.


It is possible to produce displays that have better gamut or CRI by using fill-in colours (e.g. yellow, emerald green, violet), and even to have better colour storage systems than RGB (IR,R,G,Y,B,V,UV anyone?), but unless you have butterfly or cephalopod eyes, you can't tell the difference!




Maybe evolution will product super AV eyes in a few generations, which will flock to buying super-high-CRI displays
 

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> www.colorlightoutput.com

Wow! Very interesting.

It is good to see a technical topic such as this discussed with hard data.

However, the projectors they have chosen to test, the way that the data is presented, and their failure to specifically disclose who is running this website is problematic.

Firstly, why have they chosen to only test white segment DLP projectors in their Table 2? Some manufacturers sell both DLP projectors with an RGB colorwheel, and DLP projectors with an RGBW colorwheel (and other variants too). Some manufacturers sell both LCD and DLP projectors, but again only DLP projectors with a white segment colorwheel have been tested. This omission and the failure to explain the selection clearly represents a bias. Without adequate explanation, the average consumer would be influenced by the fancy website and the incomplete data to assume that Epson, Hitachi, Sony = GOOD; and Acer, BenQ, Casio, etc = BAD. But this is an incorrect conclusion based on the incomplete data, hence the accusation of bias.

Secondly, although they try to suggest that this is all open handed and fair by pointing to the SID IDMS, their failure to clearly disclose who has funded and develop this website makes it look like they're got something to hide.

I only found two mentions of the 'owner': The 'Buyer's Guide' lists an email address for a 3LCD.com employee , and the very last page on the site 'Feedback' lists this at the bottom of the page: "Copyright © 2012 3LCD Business Center All Rights Reserved"

For those who know about projectors, and knowing who is behind this website, it becomes clear what is going on.

In Australia I think this site would sail very close to breaching consumer protection law - perhaps this would be the case in other regions too.


On the positive side, hopefully this will encourage all manufacturers to publish the CLO values of their projectors, plus clearly specify the types of colorwheel used (RGB, RGBW, RGBCYW), the colorwheel speed, and also the brightness (luminance) of projectors when they are switched into 3D mode.


Best,

Andrew.
 

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The only place I know of where they issue RGB separation graphs in their reviews is ixbt.com . I agree this aspect of projectors is very important and it is very good it's now formalized and known as CLO. However I also believe that this particular site > www.colorlightoutput.com
BenQ W7000: WLO - 2000, CLO - 1500. W7000 can achieve 2000 lumens in High Lamp dynamic mode with Brilliant Color On. However it is known what BC does to CLO:


BC on (W7000, graph taken from ixbt.com)



BC off (W7000, graph taken from ixbt.com)



As you can see, the separation is almost perfect and CLO should be very close to WLO.


Epson 5010 (profile Dynamic)



Epson 5010 (profile Cinema)
 

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Quote:
Originally Posted by Matt Cowan  /t/1451895/epson-color-light-output-demo-at-ces-2013#post_22843437


Of interest is that if one wishes to replicate colour dynamics of film on the digital projector, a projector with color lumens = white lumens will be throwing away bitdepth in the saturated primary colors. On the other hand, if the primary colors match the luminance of film (relative to peak white), the projector will use the full bitdepth to represent the colors.
I'm not quite following this. Could you perhaps explain this a bit more please?
 
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