Originally Posted by skylarlove1999
You taught me more about lumens, color and lamp/laser technology in one post then 10 years really exploring this projector and home theater hobby. Thank you once again for taking the time to break it down in a way I could easily understand. You have a great way of explaining complex things in a simple way. It truly is a gift. Would you happen to be a professor? Just curious thanks again. Laser will be the game change for HDR in a projector but the cost will be prohibitive until more people give up their televisions and use a projector so quantity can help reduce individual acquisition cost.
Wow, thanks! I'm not a professor, but I studied engineering in college and went on to practice patent law for a bit, and of course I'm an A/V hobbyist.
The concepts of lumens, lux, nits, and foot-lamberts are not that complicated, but the units are very confusing. All you need to remember is that foot-lamberts is lumens divided by square feet, and 1 foot-lambert = 3.46 nits = 10.764 lux. You then multiply by screen gain to get your final brightness.
So on a 100" (which works out to 29.7 sqft) 1.0-gain screen, a 2600-lumen projector (like the 5050UB) will produce an image with brightness as high as 87.54 foot lamberts (2600/29.7) or about 300 nits. A .9 gain would reduce that brightness by 10% (to around 79 foot-lamberts / 270 nits), and a 1.3 gain screen would increase brightness (to 114 foot-lamberts or 390 nits). Real-world figures are usually lower from generous specs, lamp aging, and light fall-off from the zoom lens.
Lux is used mostly on equipment and not in specifications/standards you'll encounter.
As much as I like using the SI system, I find it easier just to use foot-lamberts and feet when doing calculations.
Since we usually measure screen size in diagonal linear inches and not square feet, estimating brightness from a projector's lumen output is not intuitive (the same projector will be less than half as bright on a 150" screen as on a 100" screen).
I may not be totally correct about DCI-P3 requiring more light filtering, but that seems to be the explanation for the filter cutting so much light, if that's accurate.