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sRGB, Color Lumens, and Calibrating Projectors 2

By Art Feierman
The projectors with the highest white vs color lumens are single chip DLP projectors (not 3 chip DLPs). Many of these projectors using color wheels have a spinning color wheel with red, green and blue filters, but others had those three, but in addition, perhaps 1/3 of the color wheel would be a clear slice. As a result, when the normal measurement of white lumens was done, you got the light source spending 1/3 of its time passing through white. Let’s say 1000 lumens. But the other two thirds of the wheel were divided between red, green and blue.   That’s great when you are pushing out white, but when you want a pure but bright red, you can’t use that clear slice at all, so you’ve lost 1/3 of red brightness compared to an RGB wheel. Also, the 2/3 of the wheel (RGB) combine to make white, but at 1/3 less white than if there was no clear slice. Add up all the white, and the RGB component, plus the clear slice component, and you have a lot more white than if you just had a straight RGB color wheel. Essentially white is higher than expected, and the red, green and blue down 1/3 in this example. If you mix white with colors, the white dominates. Things are out of balance. If you try to calibrate a projector with a large clear slice, you find that you have to reduce brightness drastically – typically by half or more, because that’s all the pure red, green, and blue you’ve got to work with. Generally for that reason, compared to a single chip DLP projector with a large clear slice (most business DLP projectors), an LCD projector, an LCoS projector, or a single chip DLP without a clear slice, these others all produce far more color lumens, and that in turn allows them to be calibrated with much higher brightness levels compared to their respective measured white lumen counts. OK, let’s continue, based on that “explanation” of color lumens. Just because a projector has high color lumens, that doesn’t mean that the combination produces the exact color balance to meet a predetermined standard, such as D65, or REC709, or sRGB for that matter. What it does tell you though is how many high quality lumens you have to work with. As a result, just because a projector has high lumen counts of each color, that isn't a promise that the projectors will calibrate using all of those lumens. It does generally indicate that when calibrating the projector, the overall brightness won’t be dramatically less unless some other factor comes into play.

What factors you ask? Epson and Panasonic, to name two LCD projector makers place a color filter (not a color filter wheel) that slides into the light path, when in those projectors “best” modes, on a couple of their projectors. They allow for a smoother more accurate calibration than without the projector.

As an example, one of those projectors calibrates with about 650 lumens with the filter in place, and1500+ lumens without the filter. Is the filter critical? No, but the ultimate desirecd result - the most accurate, and natural looking color - will be slightly better with it in. Why would these companies (or you) be willing to give up up all that brightness?

Easy. In a proper home “theater” or cave – fully darkened, and ideally with darker surfaces – ceilings walls and floors (no I’m not calling for all black but at least dark shades of the colors being used), combined with a typical screen (gain between 1.1 and 1.3), you only need about 400 lumens to fill a 100” screen. So, even our example with about 650 lumens is bright enough to offer the same brightness as your local theater, while filling a 150 inch diagonal screen.

Or, the shorter answer would be: Why not use a filter to further refine color accuracy, if you have a properly darkened room so don't need the extra brightness? Exactly!

It’s when you want – or can’t help having ambient light, that you need more than a few hundred or so lumens. Ambient light is going to affect everything. It’s going to affect the color balance of what bounces off the screen and hits your eyes. It’s going to reduce color saturation drastically. In other words, ambient light in the room creates some of the same problems as using a clear slice on a color wheel.

So let’s get back to the basics:

If ambient light is present, all of the good things you want to achieve are compromised. Sometimes drastically! Certainly contrast goes to hell, and so does color saturation. One non-scientific term we can use here with a fair amount of ambient light is: “washed out.”

Washed out is not a desirable trait to have. So, the good news is the big shift in projectors starting back about 10 years ago, was increased brightness. Not because you need it in a dark theater environment, but so you can have some lights on, or light coming in from windows when you don’t want the theater fully dark.


Sports viewing is probably the best example of when you might want some ambient light. When I’m watching sports, either in my theater projector or my living room projector, I don’t want my room dark. I certainly don’t if I have friends over, but even without, my preference would be low to moderate room lighting. It’s more social.

When I'm watching sports, I’m not trying to obtain that ultimate immersion and “suspended disbelief” that is the reason we all like the large screen for movies. For me, when it comes to sports, it’s more of a simple “bigger is better” philosophy.

By my take, the larger the projector’s image, the more fun. Watching 8 football games at once with DirecTV’s GameMix, and each being about 30 inches diagonal, is a trip. Awesome.

That takes me back to our previous example – a 2400 lumen projector with roughly 650 lumens with filter in place, but still a great looking 1500+ lumens, and capable of hundreds more (but unbalanced color – strong greens and yellows). Somewhere in the 1500 to 2400 lumen range you would be able to compromise between maximum brightness passable color and still pretty bright, with far superior color. That “far superior” color will almost rival the “best” modes (in that case – with filter in place, such as that projector’s THX certified mode). Thus, that brighter, mode with “superior color” what you want when ambient light is present.

Expect this: looking at the first widely publicized sRGB projector, the BenQ HC1200, this projector claims 2800 lumens. But, it’s color lumens weighed in at 1740. That’s actually very good, almost 2/3 of the maximum. Most typical single chip DLP projectors are more likely to have half the color lumens (or less) compared to their white lumen counts.

The Bottom Line

Being an sRGB projector does not mean it’s a better projector, color wise. Being a projector with high color lumens doesn’t either. It’s what the manufacturer does with it.

Having the sRGB simply means there’s a high quality picture mode that produces very good color, that is, assuming the manufacturer did a good job on creating the color tables, and therefore the output meets sRGB specs.  That same could be said of any projector with a THX mode, except THX certifies those projectors.  So sRGB is more like other best modes on most home projectors.  Typically those are called“Movie” or “Theatre” or “Cinema” mode.  Consider sRGB to be another of those in that:

It promises excellent color, but no one is certifying the color as meeting the standard.

Having high Color Lumens doesn’t mean you have great color. Look at the brightest mode of virtually any projector, any technology, and you can expect to find a color balance that has some problems. That’s true of the brightest mode of the BenQ HC1200, or that LCD example (Epson 5030UB). Both have at least one brightest mode which does not have well balanced color.

Typically, the better and best modes on any projector (assuming there’s a significant range of brightness), will be less bright, in exchange for better color.

sRGB (properly implemented) means excellent color and saturation, similar but does not use the same standard used for movies or HDTV.   The “best” mode of most projectors already did that. On some projectors they might have both an sRGB mode and a “Cinema” mode that are near identical.

A poorly designed sRGB mode doesn’t get the job done. If the sRGB output is certified to meet the standard, then that’s just like calibrating any projector. If not certified, it’s just a promise of potential, but doesn’t guarantee that the projector meets that potential.

Remember there are other variables affecting color balance, such as the lamps that vary from unit to unit, and color shifts that normally occur with a projector lamp over time.

Demonstration images:  

I’ve noticed that for the most part, the new projectors touting their sRGB modes tend to show really awesome images to prove their value. The short BenQ HC1200 slideshow we’ve posted in our Projector Reviews TV section of our site, focuses on extremely vibrant colors – reds, greens, any color. These images are selected for the dynamic strength.

The tougher test for any projector is handling subtleties: Skin tones, low light scenes, etc.

It’s pretty easy for any projector to look great in its better modes, (as shown by those images on the last page) of a business/education projector.

Trying to a peacock’s feathers, or the New Mexico balloon festival, guarantees vibrant.   It’s a lot tougher to reproduce an image like this:


sRGB – a good thing.   High Color lumens – a good thing. A calibrated picture – a great thing. Both sRGB mode and high Color lumens are good indications that you can get a bright calibrated image, but neither guarantees that.


Another lower cost single chip DLP projector (no sRGB mode), this in "Movie" mode


So, at the end of the day, it comes down to how well the projector delivers on those promises. Folks that’s why we write reviews.   If we didn’t you might presume that a 2003 LCD projector with sRGB produces just as good a picture as a brand new sRGB projector today. There are many other factors, and either way, the projector must deliver an accurate adherence to that sRGB standard, it can’t be a sloppy mode labeled sRGB.

And that folks is why we still review projectors.

What's on paper, and the reality, are often very different.  The manufacturers can tout their sRGBs and their Color lumens, and THX modes, etc. But, do they deliver on those promises?  The ones that do deliver on their promises, are the ones most likely to be the better overall projectors.

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