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#### thegratingone

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I'm building a theater with pretty good light control (no windows).

How many ftLs do you think I need to make sure the image has real pop on a 16x9 screen?

If I know that, I will then work back to the projector brightness, screen size, gain, etc.

Thanks.

#### Namlemez

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Most people usually aim for 15.

#### thegratingone

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Quote:
 Originally posted by Namlemez Most people usually aim for 15.

I know I'm getting picky here, but is 15 "ok", or "really nice"? I will accept a smaller screen for "really nice", but need to know where to draw the line.

Thanks, I appreciate the help.

#### Rosano

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How do we to 15....what is the formula?

#### thegratingone

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Quote:
 Originally posted by Rosano How do we to 15....what is the formula?

[Lumens / Square feet of screen] * Gain

So, for 1000 light projector, and 10' screen (which has about 55 square feet of area), w/ 1.3x gain screen, you get:

1000/55 * 1.3 = 23.6

If I'm getting it wrong somebody speak up!

#### Glimmie

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The spec for a typical theater is 16fl.

#### thegratingone

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Quote:
 Originally posted by Glimmie The spec for a typical theater is 16fl.
Is more necessarily better? Given a dark room, I assume 16 looks good. But, in the same room, will 30 look better, or is there little gain from brightness beyond what's necessary?

Thanks.

#### Daniel Hutnicki

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I think that 15 would be at the very low end. Stewart recommends nothing less than 16 and you should be at least 18.

#### Rosano

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But the question is....is more better? Or is there a theoretical limit?

#### thegratingone

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Quote:
 Originally posted by Rosano But the question is....is more better? Or is there a theoretical limit?
Yes, that is the question! It's very helpful to find out that 16-18 is necessary, but I'm trying to figure out if 16-18 will be great, or if I need more if I want it to really look good.

#### jdhancey

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The SMPTE for commercial theaters is 16 ft-lamberts. However, this is for a projector that is open gate (projector on, no film, shutter mech. off). Therefore, the actual number is significantly lower, perhaps, 9 or 10.

#### thegratingone

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Quote:
 Originally posted by jdhancey The SMPTE for commercial theaters is 16 ft-lamberts. However, this is for a projector that is open gate (projector on, no film, shutter mech. off). Therefore, the actual number is significantly lower, perhaps, 9 or 10.
Not sure I understand. Are you saying that 16 in my home theater (dark room) is actually better than a commercial theater?

Thanks.

#### jdhancey

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Yep. Well, brighter anyway.

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I'm not really sure what you mean by "better". Too bright and the colors will wash out. Too dark and you lose fine details. Also, a calibrated projector tends to put out less than the advertised amount of ftLs. You really shouldn't decide on screen size this way. Distance from screen to seats and throw distance of projector come into play. It's no use getting a huge screen that the projector can't fill.

#### Daniel Hutnicki

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16 is used for several reasons. One the bulb does loose some of its lumens after a while and secondly and most importantly, there has always been a feeling in the industry that adverterised lumens of a projector were a little bit overestimated. In reality, you could go with 8ftlb assuming the lumen count was dead on and it never fluctuated. However, since we live in the real world, we use 16 to insure proper level of ftlb

#### noah katz

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The theater standard was set because any brighter mad=kes film flicker objectionable. Today's CRT and digitals pj's don't flicker and aren't subject to that limitation.

I think the target should be 25 ft-L. I find most theaters too dim, often having to look for shadows in day scenes to tell whether it's a sunny or cloudy day.

A brighter image is more vibrant and real-looking, adding to the perception of solidity and 3-D.

#### Jonmx

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Using anything below 25 to caculate is risky. Bulbs getting dimmer over time and light output is usually exagerated by projector manufacturers as is screen gain. Then again I have a light controlled room with over 100 ft-L and I have never had one person suggest it was too bright.

#### Brandon B

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Quote:
 Originally posted by Jonmx Then again I have a light controlled room with over 100 ft-L and I have never had one person suggest it was too bright.
Ditto. Well, Mr. Wigggles claims it is in other threads here, but no one in person.

BB

P.S. Actually, my room is not light controlled, but guests have only seen the PJ after dark, so in effect it was.

#### Chris Sander

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I find a super bright image when the surrounding environment is completely dark can sometimes hurt my eyes, similar to the feeling of turning on the light in the middle of the night. This is only a problem when the image goes from a really dark scene to a really bright scene. That flash can sometimes be painful if the brightness is too high. Also movies with lots of flashing make me want to squint if the brightness is too high. Perhaps I am just sensitive to this kind of thing.

I'm running a 92" (80" wide) Firehawk with a Sharp Z10000. IMO, in the high brightness mode the picture is too bright when all the lights are out. That is ok with me, because high contrast mode looks a lot better, and is the perfect amount of light. Still lots of punch, but it never makes me want to squint.

If you go by the specs for my setup:

high brightness mode:

projector - 800 lumens

screen - 1.35 gain

area - 25 sq. ft.

ftL - 43.2

high contrast mode:

projector - 500 lumens

screen - 1.35 gain

area - 25 sq ft.

ftL - 27

I would imagine the projector is probably closer to 450 lumens as I have a couple hundred hours on my bulb and it is definitely a bit dimmer than it was when new. Also the Firehawk is 1.35 gain if you have absolutely no angle in viewing. I imagine from my seating position it is lower, like 1.1. So that brings it down to 19.8 ftL in reality.

I should also note that viewing distance makes a difference in the squint effect. I sit at 1.5 the screen width, but others liike to sit back further around 2.0 the screen width. I noticed when sitting further back, the brighter image was not as objectionable.

Just my observations. I didn't mean to write an essay, but that is what it turned into.

Chris

p.s. I don't have a light controlled room (although it will soon be more light controlled), so I find the high brightness mode is very nice in the daytime, but 40 ftL is not enough. I would be much happier with >100 ftL for daytime viewing.

#### JHouse

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You will most enjoy between 35 and 50. Brighter images do reveal much more detail. There was a really high end dream standard for theaters established some years back by a bunch of eggheads and they decided the optimum ftL was about 50. The ran the film faster to avoid the flicker that requires a dimmer image so as not to be objectionable. Of course, the standard was too expensive to implement, and they went broke, but the picture was fab. I watched between 70 and 100 over at Wigggles' place and the only drawback was drool on my shirt. Aim for optimum. Don't just repeat the compromises of the past.

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