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post #1 of 17 Old 08-15-2019, 07:46 PM - Thread Starter
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Some basic questions on ANSI lumens

Some basic questions on ANSI lumen


I'm looking at a newly released budget normal throw projector that is vague on the brightness specification, and would appreciate if anyone can kindly clarify the following before ordering :



1. Is the measurement taken at the lens or screen?
2. If screen, what's the distance used? Size and gain of screen?
3. Does the actual brightness depend on screen size and distance?
4. Any suggestion for the lumen required for 120" screen at 3.5-4m distance?


Many thanks and best regards,

Last edited by qoopy; 08-15-2019 at 07:55 PM.
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post #2 of 17 Old 08-15-2019, 09:56 PM
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Quote:
Originally Posted by qoopy View Post
Some basic questions on ANSI lumen


I'm looking at a newly released budget normal throw projector that is vague on the brightness specification, and would appreciate if anyone can kindly clarify the following before ordering :



1. Is the measurement taken at the lens or screen?
2. If screen, what's the distance used? Size and gain of screen?
3. Does the actual brightness depend on screen size and distance?
4. Any suggestion for the lumen required for 120" screen at 3.5-4m distance?


Many thanks and best regards,


Tell us the make and model and we'll tell you if the numbers are believable.

Measurements at the screen are in nits (metric) or foot-lumens (imperial) and you multiply the screen measurements times the screen area to get lumens.

You want about 16fl for HD and ~25fl for HDR but these are not hard and fast and room conditions are important. In a dark room, with dark walls, 16fl seems to work OK for HDR as well, IMHO.
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post #3 of 17 Old 08-16-2019, 09:45 PM - Thread Starter
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Quote:
Originally Posted by DunMunro View Post
...Tell us the make and model and we'll tell you if the numbers are believable. ....
Naughty, naughty, naughty. Be a good sport and spare these folks the embarrassment.

First, thanks for the kind reply. Let's use the 25fl you gave as an example. Converted into metric, this is about 85 cd/m2 (nits). A 120" screen has an area of about 4m2, yielding a total luminous intensity of 340 candela . Is the math correct?
So, how does this translate into lumens?
Many thank and best regards,

Last edited by qoopy; 08-16-2019 at 09:49 PM.
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post #4 of 17 Old 08-17-2019, 01:23 AM
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Quote:
Originally Posted by qoopy View Post
Naughty, naughty, naughty. Be a good sport and spare these folks the embarrassment.

First, thanks for the kind reply. Let's use the 25fl you gave as an example. Converted into metric, this is about 85 cd/m2 (nits). A 120" screen has an area of about 4m2, yielding a total luminous intensity of 340 candela . Is the math correct?
So, how does this translate into lumens?
Many thank and best regards,
A 120in 16x9 screen = 42.6ft2 so if we measure 25fl at the screen, the total lumens = 42.6ft2 x 25fl = 1065 lumens.
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post #5 of 17 Old 08-17-2019, 08:31 PM - Thread Starter
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Quote:
Originally Posted by DunMunro View Post
A 120in 16x9 screen = 42.6ft2 so if we measure 25fl at the screen, the total lumens = 42.6ft2 x 25fl = 1065 lumens.
Thanks for the kind reply, DunMunro.

1. If we scale it by the factor 1/π, 1065 lumens=339 candela for a 120" screen, correct?

2. More projectors are now using nits (cd/m2) to specify brightness. 250 seems to be a popular number being used. Assuming this is measured on a 120" screen (area 4m2), it would produce a total of 1000 candela, which is equivalent to 3141.6 lumens. Is this correct?

Many thanks and best regards,
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post #6 of 17 Old 08-17-2019, 09:03 PM
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Quote:
Originally Posted by qoopy View Post
Thanks for the kind reply, DunMunro.

1. If we scale it by the factor 1/π, 1065 lumens=339 candela for a 120" screen, correct?

2. More projectors are now using nits (cd/m2) to specify brightness. 250 seems to be a popular number being used. Assuming this is measured on a 120" screen (area 4m2), it would produce a total of 1000 candela, which is equivalent to 3141.6 lumens. Is this correct?

Many thanks and best regards,
Those numbers seem correct. However any projector that uses nits to specify output also has to provide the total area of the screen.
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post #7 of 17 Old 08-18-2019, 11:06 AM
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For a more detailed explanation try reading Lifewire's story on Nits, Lumens, and Brightness — TVs vs. Video Projectors

lifewire.com/understanding-nits-lumens-brightness-4125499
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post #8 of 17 Old 08-18-2019, 06:05 PM
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Quote:
Originally Posted by qoopy View Post
Naughty, naughty, naughty. Be a good sport and spare these folks the embarrassment.

First, thanks for the kind reply. Let's use the 25fl you gave as an example. Converted into metric, this is about 85 cd/m2 (nits). A 120" screen has an area of about 4m2, yielding a total luminous intensity of 340 candela . Is the math correct?
So, how does this translate into lumens?
Many thank and best regards,

so your going for the *pro ha
even in their bbs they are still asking about it's lumens & some are speculating between 1500~1900 ANSI

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post #9 of 17 Old 08-19-2019, 11:12 AM
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NITS IS A WORTHLESS NUMBER IN THE PROJECTOR WORLD!!!!

Anyone who uses nits for a variable sized display like front projection is simply out of their mind.

Lumens is the proper measurement, and it should always be given as total lumen output. If you have a 1 square foot screen, then that's the reading the light meter should give.

Typically light meters give results in nits, as that's a proper measurement for that specific location, but it's easy enough to convert to lumens.

Having 20+ lumens per square foot is a good real world measurement to have, but there is one key thing in all of this which is missing:

WHAT IS THE MANUFACTURER THAT YOU ARE LOOKING AT WHICH DOESN'T ADVERTISE THEIR LUMEN OUTPUT?

People on these forums are more than happy to help direct you towards a solid theater solution, but be wary of cheap Chinese models with top shelf lies as their specification claims (common on Amazon) and manufacturers without a real website, etc. The 'white van scams' manufacturers are all over the place.

Typically, most major brands have decent projectors which can deliver a 100-133 inch image diagonal without any issue whatsover with quality that ranges from 'acceptable' to 'excellent' depending on your budget.

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post #10 of 17 Old 08-19-2019, 11:23 AM
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Quote:
Originally Posted by Dave in Green View Post
For a more detailed explanation try reading Lifewire's story on Nits, Lumens, and Brightness — TVs vs. Video Projectors

lifewire.com/understanding-nits-lumens-brightness-4125499
I would clarify and disagree with one statement in this article...

The conversion from nits to lumens is not ANSI LUMENS, but it is LUMENS/meter squared. That is the proper and accurate conversion. So, 1 nit (which is already required to be in square meters) is the same as 3.426 lumens/sq. meter. It is not at all equal to 3.426 ANSI lumens, because ANSI lumens doesn't demand 'square meter' as the size, and a size really must be specified.

They do throw in the added 'getting more precise' section, which is really the entirety of why their definition is completely inaccurate. A 65" display with 200nits has four times the luminosity of a 32" display with 200nits. A projector recreating that 32" image needs 1/4 the light output as a projector creating a 64" image with the same brightness. This doesn't match at all with what they said before all of this.

I would also say that ANSI lumens, coming from America, is a standard that typically would be rated over a square foot, not a square meter (welcome to the Imperial standard). So, when a projector says it is 1,500 lumens, that would be a projector that would register 1,500 lumens, over one square foot, on a 1.0 gain screen.
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post #11 of 17 Old 08-23-2019, 12:16 AM - Thread Starter
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Quote:
Originally Posted by DunMunro View Post
Those numbers seem correct. However any projector that uses nits to specify output also has to provide the total area of the screen.
You are absolutely correct. Here are some more numbers to do a comparison with a TV:

A. 77" 2019 OLED TV:
HDR Real Scene Peak Brightness: 593 cd/m²
HDR Peak 2% Window: 689 cd/m²
HDR Peak 100% Window: 130 cd/m²
HDR Sustained 100% Window: 126 cd/m²

B. 100" Triple-laser UST;

400nits

C. 120" projector bright enough for dark room:
1065lumens

Two question:
1. Which brightness number would you use to compute TV's lumens output? If 100% window sustained brightness is used, the lumens output would come out lower than the 120" projector. If Real Scene Peak Brightness is used, the lumens output will be on par with the UST. Which one looks more plausible?

2. Not being bright enough is one common complain of OLED, but it actually has higher nits rating than the 120" projector. What other factors are at play here?

Many thanks and best regards,
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post #12 of 17 Old 08-23-2019, 12:46 AM
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Quote:
Originally Posted by qoopy View Post
You are absolutely correct. Here are some more numbers to do a comparison with a TV:

A. 77" 2019 OLED TV:
HDR Real Scene Peak Brightness: 593 cd/m²
HDR Peak 2% Window: 689 cd/m²
HDR Peak 100% Window: 130 cd/m²
HDR Sustained 100% Window: 126 cd/m²

B. 100" Triple-laser UST;

400nits

C. 120" projector bright enough for dark room:
1065lumens

Two question:
1. Which brightness number would you use to compute TV's lumens output? If 100% window sustained brightness is used, the lumens output would come out lower than the 120" projector. If Real Scene Peak Brightness is used, the lumens output will be on par with the UST. Which one looks more plausible?

2. Not being bright enough is one common complain of OLED, but it actually has higher nits rating than the 120" projector. What other factors are at play here?

Many thanks and best regards,
That's not really a simple question or one that I can really answer. A projector used in a darkened room might seem superior in brightness to a TV used in a lit room, but that's about as far as I can go. However, if you want to really appreciate 4K you'll have to sit really close to the TV.
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post #13 of 17 Old 08-23-2019, 06:39 AM
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Quote:
Originally Posted by qoopy View Post
You are absolutely correct. Here are some more numbers to do a comparison with a TV:

A. 77" 2019 OLED TV:
HDR Real Scene Peak Brightness: 593 cd/m²
HDR Peak 2% Window: 689 cd/m²
HDR Peak 100% Window: 130 cd/m²
HDR Sustained 100% Window: 126 cd/m²

B. 100" Triple-laser UST;

400nits

C. 120" projector bright enough for dark room:
1065lumens

Two question:
1. Which brightness number would you use to compute TV's lumens output? If 100% window sustained brightness is used, the lumens output would come out lower than the 120" projector. If Real Scene Peak Brightness is used, the lumens output will be on par with the UST. Which one looks more plausible?

2. Not being bright enough is one common complain of OLED, but it actually has higher nits rating than the 120" projector. What other factors are at play here?

Many thanks and best regards,
@DunMunro is correct.

To elaborate a little brightness is brightness you can compare the output spread over a given screen size and get a unit brightness.

Perceived brightness is a totally different thing as our eyes adjust 22f stops providing comfortable vision for us over a wide range of light conditions. If you remember back to manual photography in the last century each f stop is a double of the one before example 1, 2, 4, 8, 16, 32, 64, 128….. do that 22 times to get a feeling of our range of light acceptance with our vision. In a normal room most people wont notice the brightness change of one f stop or twice the brightness. Reason being when the light doubles the eyes iris corrects and halves the light.

I don’t really understand all that goes on with HDR signals it is clear people are excited about it and seem to love it. but how it works in a darkened projector room sure seems it has to be different than a bright display in a bright room. I always thought SDR covered my needs in a dark theater well and I have some movies where I even thought the range was uncomfortable. I’m sure it has a lot to do with how the directors use this new tool they have.

Bud
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post #14 of 17 Old 08-23-2019, 08:31 AM
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AND THIS IS THE BS I'M SPEAKING OF!!!!

Quote:
A. 77" 2019 OLED TV:
HDR Real Scene Peak Brightness: 593 cd/m²
HDR Peak 2% Window: 689 cd/m²
HDR Peak 100% Window: 130 cd/m²
HDR Sustained 100% Window: 126 cd/m²

cd/m² is the same as nits. That's a 1:1 conversion. So, anytime you see cd/m² you can just say - 'nits'.

OLED is a phenomenal technology, and reviews of them tend to be very strong.

Quote:
B. 100" Triple-laser UST;
Quote:
400nits
So, they are saying that this projector puts up 400nits on a 100" screen?
LET'S DO THE MATH!!!!
It is a 2.775 square meter screen which is about a 29.6 square foot screen.
A direct conversion of 400 nits to lumens gives us 37.16 lumens per square foot.
400 nits * 2.775 gives us total light of 1,110 (lumens)
37.16 ft/lm * 29.6 gives us total light of 1,100 lumens total.

So, nits times the screen size will give us the lumen output of the projector. Instead of just saying it is a 1,100 lumen projector, they confuse the matter by talking about nits.

Quote:
C. 120" projector bright enough for dark room:
1065lumens
If the goal is 15-18 lumens per square foot (as it should be) then a 120" diagonal is about 43 square feet. 43*18 is 775 lumens. That's really all that is needed in a dark theater space to produce an excellent image. 1000+ lumens gives us over 23 lm/ft². That's a bit more than is needed in a dark space, but it is nice for lamp aging and for 3D viewing and will help with HDR content.


Quote:
Two question:
1. Which brightness number would you use to compute TV's lumens output? If 100% window sustained brightness is used, the lumens output would come out lower than the 120" projector. If Real Scene Peak Brightness is used, the lumens output will be on par with the UST. Which one looks more plausible?
This is why nits are used with TVs and why numbers are all over the place. HDR makes it so that absolute peak brightness is used for specular highlights, and white fields are used rarely in actual television production. Snow scenes and such. Fade to white... But, this exemplifies why the numbers for TVs and even projectors are often so meaningless without an actual review and without real world measurements.

Quote:
2. Not being bright enough is one common complain of OLED, but it actually has higher nits rating than the 120" projector. What other factors are at play here?

Many thanks and best regards,
Doing the math, you may not have realized that both the UST and the 120" projector basically are claiming the same number of lumens. This is why lumens is typically given, because you are measuring the total light output of a projector. I would think that if nits is used as a standard for a projector, then it would be over one square meter as 'the standard', while lumens is given as a total number, but it is actually over one square foot. A 1,000 lumen projector is 1,000 lm/ft². If 1 m² is the standard for how nits are measured with projectors, then a 10763 nit projector (for 1 m² would be the exact same 1,000 lumen projector.

This all gets extremely convoluted between the different measurements and calculations which are available out there and the conversion between metric and imperial. The hard part of all of this is that nits are supposed to be a measurement of light output over a square meter. If a screen was exactly 1m² and the screen used was a true 1.0 gain, then it would be a good standard form of measurement, but with light typically measured directly from the projector and calculated to a much larger size, then the lumen makes more sense.

At the end, it is still contrast which matters most, and that's why with OLED the different measurements are given and it is why a projector review is far more important than the specifications on paper.

I may have some incorrect math here and would be happy to be corrected and learn something new.

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post #15 of 17 Old 09-03-2019, 02:33 AM - Thread Starter
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Quote:
Originally Posted by DunMunro View Post
That's not really a simple question or one that I can really answer. A projector used in a darkened room might seem superior in brightness to a TV used in a lit room, but that's about as far as I can go. However, if you want to really appreciate 4K you'll have to sit really close to the TV.
Greetings DunMunro.

77" OLED
Due to the power limiting action of ABL protective circuitry, HDR Sustained 100% Window Brightness seems like a reasonable candidate to use for computing the total lumens output of OLED TV. If this understanding of the rting numbers is correct, the 77" OLED would have about 650 lumens.

100" 400nits UST
Using the same math, one arrives at 3468 lumens output. Quite a huge difference.

How do you like these numbers?
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post #16 of 17 Old 09-05-2019, 03:28 PM
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Quote:
Originally Posted by qoopy View Post
Greetings DunMunro.

77" OLED
Due to the power limiting action of ABL protective circuitry, HDR Sustained 100% Window Brightness seems like a reasonable candidate to use for computing the total lumens output of OLED TV. If this understanding of the rting numbers is correct, the 77" OLED would have about 650 lumens.

100" 400nits UST
Using the same math, one arrives at 3468 lumens output. Quite a huge difference.

How do you like these numbers?
Please re-read my post. The UST projector is more like 1,100 lumens from what I can tell. They are trying to mess with the numbers.

77" screen is about 17.57 square feet.
130 cd is about 37.94 fL
37.94x17.57 = 666.6 total lumen output.

The big difference being that HDR is all about specular highlights. So, if you were to just look at the sun glinting momentarily off a mirror, that sustained brightness would be effective to a 3,500 lumen projector over that same 77" diagonal. Yes, projectors do get this bright, but they often have terrible contrast and at 77" it would be a pretty small image. Most calibrated home theater projectors are closer to 800-1,400 lumens.

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post #17 of 17 Old 09-05-2019, 05:20 PM
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Originally Posted by AV_Integrated View Post
Please re-read my post. The UST projector is more like 1,100 lumens from what I can tell. They are trying to mess with the numbers.

77" screen is about 17.57 square feet.
130 cd is about 37.94 fL
37.94x17.57 = 666.6 total lumen output.

The big difference being that HDR is all about specular highlights. So, if you were to just look at the sun glinting momentarily off a mirror, that sustained brightness would be effective to a 3,500 lumen projector over that same 77" diagonal. Yes, projectors do get this bright, but they often have terrible contrast and at 77" it would be a pretty small image. Most calibrated home theater projectors are closer to 800-1,400 lumens.
I should have looked at the UST numbers more closely, but the standard conversion for nits to fl is nits/3.43 or 400/3.43 for the UST so for the UST this is 116.6fl x 31.3ft2 = 3649 lumens so I assumed this was correct.
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