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A question of lumens

4K views 21 replies 6 participants last post by  lcaillo 
#1 ·
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
 
#2 ·
#3 ·
Can't you use your spot meter to find how many lumens your PJ is really shooting? Just shoot a 100% white field and take a reading.

I don't think I've ever seen a definition of what makes a "light cannon" or a "low lumen" PJ.:scratchhead:

I know in testing I had a very watchable image with my BW screens at a measured 12 foot lamberts brightness. I don't think most would call that screen as being hit by a "light cannon".
 
#5 ·
Can't you use your spot meter to find how many lumens your PJ is really shooting? Just shoot a 100% white field and take a reading.
Yep I could and I think I will get a before and after when the new bulb arrives. And maybe a before and after calibration on the new bulb.

I don't think I've ever seen a definition of what makes a "light cannon" or a "low lumen" PJ.:scratchhead:

I know in testing I had a very watchable image with my BW screens at a measured 12 foot lamberts brightness. I don't think most would call that screen as being hit by a "light cannon".
And I seriously doubt that I'm at 12 fL. I'd guess 9. And my image is very watchable, even with the high hours on the bulb. I just had 5 people over on Monday night and they all sat with their mouths agape. One kept insisting that I had to set him up with a pj and screen.

If memory serves me, light canon was anything over 2500 lumens. But then again it depends on whose definition. Low lumen was any projector that needed total light control while viewing.
And then it depends on who's doing the lumen measurement too I suppose. I know there's a couple folks from LumenLab using Black Widow. And I'd call those 'lower lumen' I guess.

mech
 
#6 ·
And also how it's measured. There was a focus on using the ANSI Lumens 9 panel average. They even tweaked the numbers a bit by having the projected full white field the same color temperature as the bulb, 6500k I believe. It's been a few years since I was involved at Lumenlab, but I think a lot projectors measured 200 - 300 lumens. A few of the better ones were up around 400. And all with a $19 e-Bay light meter. I think I still have mine. Blackout cloth was the screen of choice.
 
#7 ·
And lumens would be equal to foot candle times square feet, right?

If that's correct I'm currently at 136 lumens...

That seems awfully low!

100% white field measured 4.6 foot candles. I measured as low as 3.9 and as high as 5.0. I took the average as that was the measurement at the center of the rectangle.

100" screen = 29.6 square feet

Someone tell me I'm measuring/converting this wrong!

mech
 
#9 ·
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.
 
#8 ·
Would this help? I found this converter from foot-candles-to-lumens.
 
#12 ·
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.
 
#14 ·
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
 
#15 ·
I agree, but rather than say "is wrong", I would use "could be wrong". :bigsmile:

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... :dontknow:

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.
 
#17 ·
Ahhh, there's that 'quickly' again. :nono: Haste makes waste, I keep proving this over and over again myself. :laugh:

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?
 
#20 ·
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. :dunno:

mech
 
#21 ·
I installed the new bulb last night and top center of my screen reads at 15 foot candles. There was 1992 hours on the old bulb.

And keep in mind that 15 is not video optimized yet. Time to calibrate... again. :gah:

I wonder how many people fail to re-calibrate after a bulb change or after X number of hours?

mech
 
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