A question of lumens - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

Old 01-01-09, 03:52 PM Thread Starter
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Steve Mechelke -mech

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Re: A question of lumens

Quote:
Harpmaker wrote: View Post
4.6 fL. is a very dim screen!

Was this a reflective measurement of the screen or a incident measurement of the PJ beam with the meter at the screen (I know your meter can do both)?

Lumen/sq ft, foot candle and foot lambert are all the same. Lux multiplied by 0.0929 = foot candles. Conversely, foot candles multiplied by 10.7643 = Lux. Lux = lumen/square meter.
That would be a dim bulb I guess! No reflective measurement, just an incident reading. I didn't have a ton of time before I left for work so I'm not 100% sure if I had the meter setup correctly. I'm going to double check it tonight. It can take incident readings a number of different ways and I was in a hurry.

Then again, my bulb does have 2000 hours on it.

So my calculation was correct in 4.6 X 29.6 = 136 lumens?

mech
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Old 01-01-09, 05:23 PM
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Bill

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Re: A question of lumens

Quote:
mechman wrote: View Post
My projector (Mitsubishi HC3000) is a 1000 lumen projector which I've seen reputable reports that when 'video optimized' it's more in the 400 lumen range. I have 2000 hours on the current bulb with a new one on the way.

Would this be considered a 'lower lumen' projector? In the past I've seen less knowledgeable folks discard Black Widow as an option for a screen because their projector was 'lower lumen'. And I know that in the past less knowledgeable folks said that "you really need a 'light cannon' for Black Widow".

What's the threshold for 'lower lumen'? What's the threshold for 'light cannon'?

mech
One thing that comes to mind is whether this is max lumens or video optimized lumens. There is a huge difference and some companies advertise actual video optimized lumens (much more realistic numbers) and other list max lumens because it makes it look more impressive.

I also agree with Mike P that the 'industry' considers 2500 lumens and up as 'light cannons', and are typically used in the business community or in a house of worship where light control is not practical.

So two Home Theater projectors both rated at 1000 lumens could be totally different animals. I too have seen the comments about 'light cannons' and personally they are referencing projectors from a bygone era. Projectors today are very bright and vibrant as compared to projectors from just a few years back.

Just about any projector today can handle an N8 shade of gray and as mentioned just a couple of years ago that would have been way too dark for most projectors. Most manufacturers seem to be more concerned with listing dynamic contrast ratio than the true lumen output. It's all a big game though because most of these numbers are obtained from optimal viewing conditions. Once less than perfect conditions exist, you can pretty much throw all those numbers out the window.

I have a formula somewhere that shows what happens to CR when even 1 lux of light is introduced into the room. CR quickly takes a dive.

Sorry if I digressed. Mech my guess is your projector is showing max video optimized lumens instead of max Ansi lumens (not necessarily what you are set at), but I can't say for certain. Call Mitsubishi, they can tell you for sure. Whether it's max or optimized, I wouldn't call it a light cannon, nor would I say it's a cream puff either.

With a gain of .9, I'd say most projectors out there could handle Black Widow, it's all a matter of personal preference like anything else. Some people like inky black while others want whites as white as possible. It's no different than how some people prefer a cool image while others like a warmer image.

Once again we get into looking at things as a whole.

12fL is the standard for minimum brightness at the screen for cinema viewing with total light control and 14fL is the THX standard. So in reality it has more to do with the screen size and room setting than how bright the projector is.

I've said this before and will be posting this in the projector forum but most people approach setting up a home theater or media room totally backwards. By thay I mean they buy the projector first and then worry about the screen. The first thing should be a review of the room conditions and setting. This will determine the optimal screen size based on the room size and viewing distance. Most people go for the largest image possible even if it is inappropriate for their room dimensions. With an honest assessment the appropriate screen size can be determined.

Next would be the lighting conditions as well as the viewing habbits. Some people only watch movies in a theater like setting while others watch television and sports on their projector. Both environments would dictate different screen types. Once the type and shade of screen is determined that suits the room conditions, then a projector should be selected that will provide the minimum required brightness for the screen and room setting.

"Make everything as simple as possible, but no simpler." - Albert Einstein

"If all else fails, spin the cat."- Grzboken
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Old 01-01-09, 06:15 PM
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Don

Join Date: Oct 2007
Location: Central PA
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Re: A question of lumens

Quote:
mechman wrote: View Post
That would be a dim bulb I guess! No reflective measurement, just an incident reading. I didn't have a ton of time before I left for work so I'm not 100% sure if I had the meter setup correctly. I'm going to double check it tonight. It can take incident readings a number of different ways and I was in a hurry.

Then again, my bulb does have 2000 hours on it.
Yeah, it would be a good idea to take another reading making sure your meter is set up correctly (you almost have to take a course to learn how to use that thing! ). I'm not making fun of mech or his light meter; that thing is a seriously wicked meter!

Quote:
So my calculation was correct in 4.6 X 29.6 = 136 lumens?
That's what I get assuming a 100" diagonal 16:9 screen. You are having 4.6 fL. of light hitting a square foot of screen, multiplying your screen footage by 4.6 gives you 136 total lumen/sq ft for the screen.

I played around with the Pro Calculator at PJ Central and your PJ in video mode is showing 14-16 fL for that screen size, depending on the PJ's zoom setting. I have found that my PJ actually shoots out about half of the fL. this calculator shows, I assume it's because I'm using Econo mode. If you are using Econo mode too that could well cut your true fL. figure down to 7-8 fL. with a new bulb! This is all supposition of course.

Take your time and get an accurate PJ output measurement and then change the bulb and take another; this will tell you what is REALLY happening with your PJ.

You all are probably getting tired of hearing me say this, but I wish people would spend the extra money (less than \$50 to your door) to get a simple light meter so they can know what their PJ's are really shooting instead of just guessing or going by a calculator that may or may not be right.
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Old 01-01-09, 06:32 PM Thread Starter
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Steve Mechelke -mech

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Re: A question of lumens

Thanks Don! I'll putz with the meter some more tonight before bed time and report back tomorrow.

What's really intriguing to me is that if those numbers were true, everything said elsewhere in the past (and more than likely currently as well) is wrong.

mech
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Old 01-01-09, 07:03 PM
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Don

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Re: A question of lumens

Quote:
mechman wrote: View Post
Thanks Don! I'll putz with the meter some more tonight before bed time and report back tomorrow.

What's really intriguing to me is that if those numbers were true, everything said elsewhere in the past (and more than likely currently as well) is wrong.

mech
I agree, but rather than say "is wrong", I would use "could be wrong".

Just as no two cars get the same exact mileage, even if they are the same make and model, no two PJ's are going to have the same light output. Take individual differences between PJ's and add in the unknown of whether the manufacturer used video or business illumination figures, and you get one big mess. Throw in PJ setting changes due to screen calibration and...

If someone could actually measure the output of projectors at various settings (business and video modes, normal and econo lamp settings) and make a table, it could be of real use to determining what PJ to use with our screen. The closest this comes to being a reality is various reviews in magazines and on the web, but even they don't take the time for as in-depth testing as I would like to see.
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Old 01-01-09, 09:47 PM Thread Starter
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Steve Mechelke -mech

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Re: A question of lumens

Ok I quickly redid it using the projectors white test pattern. 11 foot candles.

11 X 29.6 = 325.6 lumens

That's a bit more realistic. So.... am I a 'lower lumen' pj guy?

mech
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Old 01-02-09, 11:18 AM
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Don

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Re: A question of lumens

Quote:
mechman wrote: View Post
Ok I quickly redid it using the projectors white test pattern. 11 foot candles.

11 X 29.6 = 325.6 lumens

That's a bit more realistic. So.... am I a 'lower lumen' pj guy?

mech
Ahhh, there's that 'quickly' again. Haste makes waste, I keep proving this over and over again myself.

Did you redo the test with both a 100% white field image and the PJ's test pattern, or just the PJ pattern alone? I would be very interested to know if they differ.

The advantage of using a 100% white field image from a known source, such as the 'Digital Video Essentials' DVD, is that it is an industry standard; I'm not sure the patterns built into PJ's are.

At 325 lumens I would say that is fairly 'low lumen'. This of course, is with a bulb that has almost reached end-of-life. I would suspect you will easily double that figure with the new bulb (or I guess I should say 'lamp'), and perhaps get even more brightness.

Now the big question: does your screen image look dim?
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Old 01-03-09, 11:29 AM Thread Starter
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Steve Mechelke -mech

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Re: A question of lumens

Quote:
Harpmaker wrote: View Post
Ahhh, there's that 'quickly' again. Haste makes waste, I keep proving this over and over again myself.
All I need is 2 or 3 extra hours in a day!

Quote:
Harpmaker wrote: View Post
Did you redo the test with both a 100% white field image and the PJ's test pattern, or just the PJ pattern alone? I would be very interested to know if they differ.

The advantage of using a 100% white field image from a known source, such as the 'Digital Video Essentials' DVD, is that it is an industry standard; I'm not sure the patterns built into PJ's are.
I revisited it again today. With the 100 IRE I was getting 12 at the brightest and 9 as the lowest. It gave the same reading as the pj lamp pattern at what I consider the brightest location from my pj - top center. I would guess if I were to check it tonight it would be a tad bit lower. I've got a tad bit of daylight coming in right now.

Quote:
Harpmaker wrote: View Post
At 325 lumens I would say that is fairly 'low lumen'. This of course, is with a bulb that has almost reached end-of-life. I would suspect you will easily double that figure with the new bulb (or I guess I should say 'lamp'), and perhaps get even more brightness.

Now the big question: does your screen image look dim?
Most definitely not. It doesn't appear to be dim at all. However, I probably have gotten used to it if it has. I'm still amazed at the image. The only reason I ordered a new bulb is because I figured it was time to put the current one on the shelf as the backup and get a new one. After thinking more about the time on the bulb, I remembered that this is not the original bulb. The original was replaced by Mitsubishi two years ago. And I'm uncertain as to whether or not the bulb timer rests itself or not. The new one arrives Wednesday. We'll know more then.

mech
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Old 01-03-09, 11:50 AM
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Don

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Re: A question of lumens

Glad to hear the 100 IRE image and the PJ's built-in white image seem to be the same; that speaks well of Mitsubishi in my book.

You are also verifying my opinion that 12 fL. is plenty of light for a BW screen.
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Old 01-03-09, 12:35 PM Thread Starter
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Steve Mechelke -mech

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Re: A question of lumens

In another 5 days or so I should be able to start doing more work. Since I already started this I'm going to finish it before moving on. Thinking about it though, the new bulb shouldn't change much. I mean it will initially I'd think. But after calibrating it should fall pretty much in line with what I have now.

mech
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