Posted on March 14, 2008 By Art Feierman
Once we get past achieving an image that looks really good (color balance, black levels, and shadow detail), to me, brightness is by far the most important attribute. It’s simple. Only a few projectors can really handle larger screens (over 110″ diagonal) very well, in Best mode. Only two are really exceptionally bright, bright enough to effortlessly handle my 128″ Firehawk screen, and even larger ones (even my JVC RS1, which in best mode is brighter than most has “just enough” for my screen).
There are several projectors that really don’t have the muscle to really go above 100″ diagonal, or maybe 106″, others are comfortable at 110″.
Consider that a 130″ screen requires a projector with 69% more lumens, than the same screen surface in a 100″ format – and that is the difference between, say 350 lumens, and 591 lumens. The first number is fairly typical of the least bright projectors, while 591 is brighter than the average projector in this group (average is somewhere around 450 lumens).
Click to enlarge. So close.
Unmatched in lumens, is the Optoma HD81-LV, image above some football, I’ve never been able to open that left blind (the shades on the doors – not in the picture, are also open), with any other projector, and still be able to watch. That’s 2500+ lumens at work!
A good guideline is to use the foot-lambert measure. The SMPTE (Society of Motion Picture and Television Engineers) recommends a minimum of 12 foot-lamberts, and recommends 16. (Remember – due to safety laws, today’s theaters are not allowed to be as dark as a really good home theater can get.) To calculate ft-lamberts, the formula is:
Foot-Lamberts = lumens / sq foot of screen (assuming a screen gain of 1.0).
If your screen has a positive or negative gain, multiply that gain times the lumens, before dividing by the screen size. For an example, I’ll use the Epson Home Cinema 1080 UB, with my 128″ Stewart Firehawk (relative gain of 1.25) numbers are rounded.
So consider, by this measure, the Epson has just barely enough brightness, in Best mode, for my setup. (I concur with that from watching it extensively). However, with 1500 hours on the lamp, the ft-lamberts will probably drop below 10. As a result, let’s say that the Epson, in my setup, has enough muscle to fill the screen, with respectable brightness, when new, but not with an old lamp.
There is another issue, which is how bright the projector can get when you aren’t seeking perfection – when you have some ambient light to deal with, and especially for HDTV/TV/Sports, since most have no desire to watch normal TV programming and sports in an almost pitch black room (can you say “cave”?). In Brightest mode, by comparison, that same Epson, in my room, when new, actually is very close to 40 ft lamberts.
Above, the Epson Home Cinema 1080 UB, in Dynamic mode, with moderate ambient light. Not bad. Shutting all the shades down, no sunlight pouring in, yields this (as you can see, still significant ambient light, but no problem for the Epson):
Also, don’t forget, that as your lamp ages, it will dim. If you expect to get the full rated life out of the lamp (that’s 2000 hours in full power for most home theater projectors), you can expect a drop of 30% or more over its life.
This poses a dilemma for some buyers. Some will pick a screen size/type in combination with projector, that is bright enough with the lamp in low power mode, and use low power mode until the lamp dims enough to kick it into high power mode, which will make up a good chunk of the lost lumens.
Because of the differences in the technologies, as well as the use of dynamic irises, etc., a projector that is particularly bright in Best mode may actually turn out to be one of the least bright in Bright modes.
As such, in some cases, those who are only interested in movie viewing in an extremely dark room, may find a particular projector perfectably acceptable, while the next person, who also watches a lot of sports, rejects that same projector out of hand, because it lacks the muscle when needed.
If your room has good lighting control, with little ambient, even average brightness projectors like this shot from the Mitsubishi HC6000, look great. For this reason, this year, I’ve decided to organize into two categories: Dark room – Best Mode, those who only watch movies, or are so into the movie aspect that they don’t really care if they are a bit underpowered for other uses. I’ll call the other Bright room. (Sounds a lot like the ISF’s ISF Night, and ISF Day settings).
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