Overview of Lumens vs. Lux in Projector Brightness Measurements
What you Need to Know
As you may have seen in my recent news article, Epson America filed a lawsuit in late November against four projector brands sold on Amazon — Vankyo, WiMiUS, GooDee, and Bomaker. Epson is focusing this suit on how these four brands do not use the industry-standard specifications and can potentially be deceptive in their claims, specifically the quoting of “LUX” instead of lumens on projectors.
Also, just recently (March 2021), Epson America announced it has reached an agreement with Philips and Screeneo Innovation that all future Philips NeoPix projectors designed, manufactured, and sold by Screeneo will use industry standard specifications (ISO 21118:2020) for brightness claims. The agreement is a result of Epson’s proactive campaign to highlight deceiving advertising that does not use industry standard specifications. To read more about this agreement, click here.
So, what is the difference between LUX and Lumens?
Projector Brightness is one of the top considerations for projector buyers. The international standard for measuring Projector Brightness is Lumens. Lumens are independent of light source or projection technology, so it applies to all projectors. ISO 21118 defines the measurement and reporting of White Brightness and IDMS 15.4 defines the measurement of Color Brightness.
Here are some of terms incorrectly used by some projector manufacturers and why they are not giving customers the full picture (literally):
Light Source Lumens
LUX – There is no standard that reports the Lux measurement of a projector. LUX and Lumens are related but are critically different. Projector LUX measures the amount of light falling on the screen. Lumens is equal to the LUX measurement times the screen area in square meters.
Light Source Lumens – There is no standard that reports Light Source measurement of a projector. White Brightness or Color Brightness of the projector has to be measured at the screen as defined by the scientifically approved standards. The two internationally recognized standards for Projector’s White Brightness and Projector’s Color Brightness both require 9-point measurements of the entire screen not the light source.
LED Lumens - There is no such thing as ‘LED Lumens’. There are two internationally recognized standards for Projector Brightness - ISO 21118 and IDMS 15.4. Both White Brightness and Color Brightness are measured in Lumens. There is no officially recognized standard for what some in the industry call LED Lumens.
LUX are NOT Lumens
We did a side-by-side comparison of two projectors, one claiming their brightness at 6,500 LUX and the other claiming 6,500 ANSI Lumens and the outcome was clear (pun intended).
While our LUX sample piece advertises their brightness as 6,500 LUX, might seem like a lot but as we discussed earlier, LUX is not a standard projector measurement so it can’t be used to compare brightness between projectors from different manufacturers (only manufacturers’ who use the industry standard of Lumens can be compared in an apple-to-apples way). It might be helpful when comparing two “LUX” rated models, but it can’t be used to compare brightness with another manufacturer’s projectors, so it is pretty much meaningless number.
To measure ANSI lumens of the two pieces, I set both projectors to their brightest modes. I also made sure the projectors were in their highest lamp mode.
I also measured brightest at full wide angle because the iris is wide open allowing the most amount of light to get through. I took 3-4 readings about 15-20% out from the center of the lens. That should give a pretty good approximation of ANSI lumens unless a projector’s brightness rolls off excessively at the edges.
Even before I measured the two units, it was obvious that the Lumens model was significantly brighter. When tested, as you can see from the photo above, the difference was significant with the Lumens-rated model nearly nine times brighter than the LUX rated model.
LUX Test Model ACTUAL Maximum Brightness: 423 lumens
Lumens Test Model ACTUAL Maximum Brightness: 3,885 lumens
Even in its ECO lamp mode, the Lumens model produced 2289lm which was more than five times the maximum Lumens of the LUX projector.
While we did not do a side-by-side comparison of the other two measurements we have seen quoted (Light Source Lumens and LED Lumens) LUX is the most prevalent and we are pretty confident we would have seen a similar result.
Higher brightness also made the colors look more vibrant especially of a larger screen or in a room with ambient light.
Buyer Beware and Be Informed
This misinformation and confusing terminology used by some manufacturers is the reason Epson has filed a lawsuit against several projector makers who measure their brightness using one of these other non-industry standard measurements. To read more about the lawsuit and the full details on some of the models who use these alternative measurement terms, visit my Industry News Article by clicking here.
It is important to understand the specifications claimed and used in selling practices so you can be fully informed when making a buying decision.
This is another reason the buy from a reputable company that lists brightness using an Lumens which is officially recognized brightness standard. Remember it get what you pay for.
These days, you can buy a good 3300lm projector like the Epson new Home Cinema 880 for as little as $499 dollars. Don’t let big meaningless LUX number trick you into buying a lower performing projector just because it is a little cheaper.
Now that you know the difference, you make the decision on what you want to buy and what will work best for your particular application, but keep in mind you often will get what you pay for. If you are comparison shopping, your side-by-side may not be apples-to-apples if one of the projectors you are considering does not publish its brightness measurement in Lumens.