Projector brightness myths debunked
A few days ago, we were testing the Sony VPL-260ES 4K home theatre projector at 1,500 lumens projector brightness. Compared to equal priced projectors boasting 2,500 lumens and knowing that some projectors go up to 5,000 lumens that doesn’t sound like a lot these days.
Yet, when we looked at the calibrated pictures on the screen in our –admittedly- dark home theatre room, we wondered how come that a projector with 1,500 lumens stated on their specs appeared brighter that another projector boasting 2,000 lumens.
Basically, that’s because one reading of lumens is not the same as another reading of lumens….
Let us explain.
What’s in a name
The average calculation of brightest white light a projector can put out is measured in ANSI lumens or just “lumens” for short. This measurement is done on a 100% white test pattern giving you the ANSI lumens reading.
That said, some manufacturers are now quoting “Centre Lumens” instead of ANSI lumens because the number is larger–measuring just the brightness at the centre of the screen rather than the average brightness overall, as the ANSI method does.
It’s fair to say that comparing ANSI rating to Centre rating is comparing apples with oranges and is a no-no.
So, our first and most important recommendation to you is to find out at what kind of lumens we are really looking at when you are reading specs in preparation of your next home theatre projector purchase.
And then there is colour brightness…
The question asked by some projector manufactures was: It’s all good and well that you are telling me how bright a white screen is, but who on earth looks at a white test screen? Isn’t it more important to know how bright projectors are when displaying full colour images?
Some heads started nodding and because of that, a few projector manufacturers also started publishing Colour Light Output (or CLO) on their specs sheet. To the untrained eye, that might appear just a different name to ANSI lumen. It’s not quite the same thing.
Unlike ANSI lumens, Colour Light Output uses a red, green and blue test pattern instead of using a 100% white test pattern. Separate meter readings are taken for red, green, and blue, then added together. Due to the way they work, for 3-chip projectors, the ANSI lumen and CLO reading will be the same. Not for the single chip DLP projectors.
For single chip DLP projectors, the CLO reading will be lower than the ANSI lumen reading. Interesting, right?
But…
Take an LCD projector (or any other 3-chip projector) at maximum brightness (and therefore with the 3 chips wide open) and chances are that you will find that the colour balance is off. And while it may be desirable to have nice colour brightness, we certainly also rate colour balance.
Your logical response will be: let’s calibrate the projector and fix the colour balance. Here’s the issue with that: calibrating your projector and adjusting blue, red and green output may affect the real brightness of your projector. In other words, once calibrated, your projected might put out nowhere near the promised 1,500 or 2,000 ANSI lumens or CLO stated on the specs.
In other words: are ANSI lumens specs or CLO specs important when you are looking for your new projector? Absolutely! Is it the beginning and the end of all? No way! We say both ANSI lumens and CLO are nothing more than a very loose indication of what your projector will do when playing in your home theatre. On top of that, when it comes to the having a great image to look at, there is a lot more to be considered than just a brightness spec.
Screen Gain
But wait, there is more…
Apart from the amount of light coming from the projector, there is another factor that will determine the brightness of picture the picture you will be looking at: the reflectivity of the screen or “gain.”
A screen with a gain of 1.0 will reflect back to the centre viewing position the same amount of light that strikes it. A screen with gain greater than 1.0 will focus more of the light energy back toward the centre viewing position and less toward the sides, making the picture look brighter when viewed from the centre position. In other words, if a screen has a gain of 1.3, it will look 30% brighter at the centre viewing position than it would with a 1.0 gain screen. If the screen has a gain of 2.0, it is twice as bright, etc.
The big downside to high gain screens is that, since they focus more of the light energy back toward the centre viewing position they reflect less light toward the sides. That means the picture gets dim for the poor viewers that sit more towards the side. This means you only want a high gain screen if you only view from the centre viewing axis. That said, it’s an easy way to add brightness to your picture. I guess, it’s a balancing act, like so many things in life.
The projector’s light output and the screen’s gain together determine how bright the overall picture looks and is typically measured in foot-Lamberts, or simply fL.
So, as the ANSI lumen measurement tells you how much projector light energy is hitting the screen, the fL measurement tells you how much light is being reflected back. In the end, that’s what really counts, we say. Easy peasy.
So how much?
As to what is the right amount of ANSI lumens for your new home theatre projector…
Depending on your personal situation (read ‘environment’) your projector will need a different brightness. While it is not the only factor to take into consideration (room size for instance being another piece of the puzzle), it certainly is a big one.
If you watch movies in a dark room a 1,500 ANSI lumens projector will do fine, provided you are not watching movies in HDR (in which case you will need more than that) Go too bright though and the image will cause eye strain.
If you are dealing with a room with some ambient light (blinds leaking some light for example), you will want to step up the brightness to be around the 2,500 ANSI lumens mark or higher.
Talking also the projector screen into account, you can use Projector Central’s Projection Calculator.
But again, we can’t stress it enough that these figures are just indications. Every projector is different, every room lay-out is different, every room size is different, every projector screen is different, every calibration is different.
On a final note
We have received a few confused phone call from people who are tossing between a large 4K HDR television and a home theatre projector with screen.
Before the introduction of HDR TV, when you decided your TV needed an upgrade, the way to tell whether one model was brighter than the other was simply to eye-ball them.
When shopping for a TV these days, consumers are now being hit with the term ‘Nits’. So, how do the terms ‘ANSI lumens’ that is used as an indication for projector brightness and ‘Nits’ relate to each other?
Well the truth is, they don’t.
Apart from the fact that, as explained before, ANSI lumens is only a vague indication of what your projector will do, there is another reason why the two terms don’t compare.
Contrary to a projector, a TV sends light directly towards you. When you talk about Nits, you talk about a measurement of how much light the TV screen sends to your eyes (luminance) within a given area.
When you talk about ANSI lumens, you refer to the light that is sent from the projector to the screen. As we mentioned before when we talked about screen gain, that light is then again reflected by your projector screen, which may or may not significantly add to the amount of light that reaches your eye (these days, some projector screens are marketed with a screen gain of 300%). So, comparing Nits to ANSI lumens is like comparing a finished dish to a half-prepped dish, to put it pretty blunt.
So…
So with all that info, what should you take from this?
First of all, no matter what figure you look at -ANSI lumens and/or CLO- you’re looking at something that is an approximation of how bright a projector image is at the very best. There are so many variables that are being ignored and that can significantly affect the quality of your image and the brightness of your image for that matter.
And secondly, when you decide to compare projector brightness between two different projectors, make sure you compare apples with apples, not apples with oranges.
We’ve spoken.:-)
Source: Projector Central, Lifewire, Projector people, Epson