FIREHAWK info now up on the Stewart website - AVS Forum
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post #1 of 26 Old 01-04-2002, 11:15 PM - Thread Starter
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FireHawk info here...
http://www.stewartfilm.com/engineeri.../firehawk.html

I see that the specs on the screen are a little different than rumored. The screen was rumored to be a 1.3 gain screen but the spec's show it as 1.35. Also it was rumored to have a 130 degree viewing angle but the spec's now show 100 degrees.

I was interested in this screen for my Sony 11HT, but I'm not sure if my theater seating configuration will benefit from the reduced viewing angle.

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post #2 of 26 Old 01-04-2002, 11:19 PM
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I wish it would state the passive gray level.

Ken Elliott
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post #3 of 26 Old 01-04-2002, 11:35 PM
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sounds perfect for a light TORUS treatment... :D
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post #4 of 26 Old 01-05-2002, 06:12 AM
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100 degree viewing angle should be acceptable for most circumstances, unless you have seating that is really off to the sides. My room should be ideal for a Firehawk as it is long and narrow, 12 x 26.
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post #5 of 26 Old 01-05-2002, 09:21 AM
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Quote:
Originally posted by kelliot

I wish it would state the passive gray level.


Ken,

The FireHawk is considerably darker, (passive gray level) than the GrayHawk.

Don
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post #6 of 26 Old 01-05-2002, 11:11 AM
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I can't wait to see one.

I sounds like it may be good for other projectors as well, like the JVC D-ILAs.

Ken Elliott
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post #7 of 26 Old 01-05-2002, 11:38 AM
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I'm having a heck of a time deciding between the Firehawk and the Grayhawk for my 11HT. I only use cinema mode, and I'm thinking of using a CC filter, so my lumens might be low enough to benefit from the increased gain. I dunno though. I'd really like to sample the two.

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post #8 of 26 Old 01-05-2002, 01:52 PM
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Quote:
Originally posted by JB72
I'm having a heck of a time deciding between the Firehawk and the Grayhawk for my 11HT. I only use cinema mode, and I'm thinking of using a CC filter, so my lumens might be low enough to benefit from the increased gain.
I am one of the lucky ones who will get to find out soon. :D Even a higher lumen projector should benefit from a Firehawk. Although it was designed and is marketed towards the lower lumen machines, being a darker grey should increase the perceived contrast ratio of any projector. I have an LT150 and a Sanyo XP21N and can't wait to play with the Firehawk.
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post #9 of 26 Old 01-05-2002, 02:49 PM
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Jonmx,

You very lucky man :). I can't wait till the reviews are out. I'm leaning towards the Firehawk.

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post #10 of 26 Old 01-05-2002, 03:57 PM
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Quote:
Originally posted by kelliot
It sounds like it may be good for other projectors as well, like the JVC D-ILAs.
We'll soon find out! I'll be testing with a G1000 and 10' wide screen (currently GrayHawk).

Can't wait!

Cheers,
Dave.
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post #11 of 26 Old 01-05-2002, 04:19 PM
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Don,

"Increases black levels"

Shouldn't that be "decreases"?

Noah
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post #12 of 26 Old 01-05-2002, 09:42 PM
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OK. I know nothing about screens, and I'm trying to make sense out of things like the viewing angle and the half gain angle.

The half gain angle for this screen is 28 degrees. So, am I to read this as meaning that any portion of the screen that lives outside a +/- 28 degree cone from my viewing position will be acting as a .68 gain screen or lower?

In this context, I have trouble understanding what "viewing angle" means. At 100 degrees off axis with a 28 degree half gain angle, I'd think the picture would be unwatchable. So, what does "viewing angle" mean?

I was planning on getting an 8' wide FireHawk. My seating positions produce angles to the edges of the screen up to 36 degrees. The primary viewing positions produce angles of about 16-27 degrees.

I'd appreciate any insights someone can provide.

Thanks.

/jab
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post #13 of 26 Old 01-06-2002, 03:39 AM
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Don,

I have just placed an order (from London) for a Greyhawk (100" 16:9). The order was placed a week before Christmas. I use an Infocus lp350 DLP projector (1300 lumins). I am now wondering if I have ordered the wrong screen. Would I be better off with this new Firehawk, and if so, is it possible to change my order?

Getting really good black levels and good snap are important to me.

Thanks David.

P.s. Ill understand if the screen for my order has been built, and it is too late!
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post #14 of 26 Old 01-07-2002, 11:08 AM - Thread Starter
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Hi Jonmx,

Quote:
100 degree viewing angle should be acceptable for most circumstances, unless you have seating that is really off to the sides.
My room is pretty similar to your (13' by 27') but I am not doing the traditional rows of seating but more of a U or V shaped seating arrangement in the front 2/3rds of the room. My wife, a.k.a "the one who must be obeyed", has decreed that if I'm going to spend the money on this room that it must be a multipurpose gathering room and not just for watching movies.

Though I intend to be the one in the primo straight-on seat, there are occasions when company will occupy the flanks. I figure I need, at maximum occupancy, a viewing angle of 130 degrees.

The interesting thing about the FireHawk is that what ever mojo is going into it to make it the perfect match for DLP projectors is also making it one of Stewart's most restrictive angled screens in their flexible screen material portfolio.

GrayHawk: .95 gain and 160 degrees
StudioTek 130: 1.3 gain and 160 degrees
UltraMat 150: 1.5 gain and 140 degrees
VideoMat 200: 1.8 gain and 120 degrees
FireHawk: 1.35 gain and 100 degrees

I'm confident that the FireHawk is going to render a beautiful picture, just a little crestfallen that it's not going to work out to be the best fit for my situation. :( Ultimately I will probably end up going with the 110" GrayHawk or StudioTek 130.

-- Gregg
 

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post #15 of 26 Old 01-07-2002, 11:19 AM
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I would also like to know more about how the viewing angle is determined. If the viewing angle isn't the half gain, then how is it determined? What exactly does the viewing angle mean, because I would imagine that even at 180 degrees, you could technically still see light from the screen. Is the viewing angle quarter gain or something?

I would also like to know how to compare the gain of Stewart front projection screens to rear projection screens. I've been looking at the listed specifications for screens on Stewart's website. Let's say you're comparing a front and rear projection screen that have the same maximum gain and the same half gain viewing angle. Would each screen have the same brightness given the same positioning of the projector (except for being on opposite sides of the screen of course)? Or do you need to somehow factor in the back scatter for rear projection to find the true brightness?
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post #16 of 26 Old 01-07-2002, 03:49 PM
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I am also confused about the geometry of viewing angles.

Simple question: If you have a 96 inch wide screen (Firehawk) and you have one row of seating 96 inches wide 12 feet back from the screen, will everyone see the screen with the same picture quality?

Raymond
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post #17 of 26 Old 01-07-2002, 07:24 PM
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Don,

Would the material you are using for the Firehawk be considered retro-reflective considering the limited viewing angle you specify?

I'm currently using the DaLite Highpower screen with my D-ILA projector and would seriously consider this new screen - I love the higher gain from my current highpower, but I would love to benefit from a darker blacks as well - this screen should be a good seller. I think you will have a lot of repeat customers who now are able to get a little more gain without sacrificing black level.

I'd love to see one.

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post #18 of 26 Old 01-07-2002, 08:08 PM - Thread Starter
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Hey Raymond,

To paraphrase, "It is better to be thought a fool and remain silent, than do math in public and remove all doubt." But, that being said, I'll take a crack at it.

Recall (in a nightmare sense) from trig, the "Rule of Sine". If you have a triangle with angles a, b and c, and sides of length a', b', and c' where a' is the side across from angle a, b' across from angle b, etc.. then a'/sin(a) = b'/sin(b) = c'/sin(c).

If you know the length of one side and 2 of the angles, you can compute the length of the other 2 sides using the rule of sine.

In your example you referenced the FireHawk which has a half gain angle on 28 degrees, so there is one angle. You also said that your straight line of seats would be 12 feet back, so we know one side. And since the line of seats is straight, there is our 2nd anlge, 90 degrees. Since all the angles of a triangle add up to 180, we know that that last angle is 62 degrees.

So using the rule of sine, 12/sin(62) = x/sin(28). Solve thru and you get x=4.3 feet. So, if you move 4.3 feet in either direction off dead center AT 12 FEET back, the picture you see will be 1/2 as bright as dead center. Since you said your row of seats was 96 inches long, no one will see less than half gain, but the far left and far right person will be very close.

Now take the GrayHawk in the same scenario. Its half gain angle is 48 degrees. That makes its equation 12/sin(48) = x/sin(42). Solving thru you get x = 10 feet. That means with the GrayHawk AT 12 FEET BACK you have to get 10 feet off center to see half the brightness from dead center. So in your 96 inch seating example, since the furthest person is going to be 4 feet on each side of center, they still see a picture that is approximately 75% as bright as on center.

And I'll finish that off with, I think that's right?

-- Gregg
 

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post #19 of 26 Old 01-07-2002, 08:22 PM
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Well, this gets back to me wondering exactly how viewing angles work. Isn't the person sitting at either end of the seating area 8' off center for their view of the far side of the screen?

So, a person sitting at the either end of the seating area has a 90 - atan(12/8) = 34 degree viewing angle to the far side of the screen, well past the half gain angle.

Right?

/jab
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post #20 of 26 Old 01-07-2002, 09:27 PM - Thread Starter
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Hi JAB,

I'm probably putting my foot in my mouth trying to answer this one, but I'm sure someone will correct me if I'm wrong. (They always do)

Gain is a funky thing. You aren't really "gaining" more light than you put in, but you are focusing the reflection back more narrowly than you would off a matte white surface. As the gain goes up, the more the light is being herded back towards where it came from.

A matt white surface tends to scatter the light in all directions. The positive of this is that the image looks great from almost all angles. The downside is that the image can look more washed out and that the walls and ceiling of the room are illuminated in the reflection. This can negatively affect your perceived contrast ratio.

A gain screen concentrates the light back toward the projector. The image is brighter and more vibrant, provided you are in the sweet spot. As you move away from the sweet spot, the picture begins to dim. The higher the gain, the smaller the sweet spot and the more aggressively the picture dims as you move off center. BUT, it may not dim uniformly.

The light from the projector is coming out in a "squared" or "rectangular" cone. The image in the dead center of the screen is coming straight from the projector, but as you move away from the center, that light is originating from some angle other than straight on. Your question was based on the assumption that the light hitting the far corner of the screen was coming straight at it as opposed to coming at some angle relative to the lens. It could be, in fact, that on a high gain screen the edge directly in front of you, in the far right seat, may appear dimmer than the far left edge of the screen because you are at a more extreme angle to the right edge of the screen relative to the center of the lens than you are to the left edge of the screen relative to the lens.

And again, I'll give myself an out with, I could be wrong.

-- Gregg
 

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post #21 of 26 Old 01-07-2002, 09:38 PM
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Now, that is interesting...

So, how do I figure out whether a FireHawk will deliver good results with my seating arrangement?

/jab
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post #22 of 26 Old 01-07-2002, 09:42 PM - Thread Starter
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Trial and error can be very effective. :) Ask Stewart if you buy a FireHawk and are dissatisfied what sort of trade in policy they have on the material. I've heard tons positive things about their customer service.

-- Gregg
 

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post #23 of 26 Old 01-08-2002, 05:17 AM
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Hi Greg,

Thanks for the geometry lesson. That was quite brave on your part.

Thanks to you, now I understand how this thing works.

Raymond
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post #24 of 26 Old 01-08-2002, 09:02 PM
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Quote:
Originally posted by noah katz
Don,

"Increases black levels"

Shouldn't that be "decreases"?
Why do I need the screen? I can increase black levels by turning my room lights up. Those marketing guys...

-Mr. Wigggles

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post #25 of 26 Old 01-24-2002, 05:35 PM
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Correction to the chart:

Ultramatte 150 Viewing Angle 140 Degrees
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post #26 of 26 Old 01-24-2002, 09:22 PM - Thread Starter
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Thanks Cain, that was a typo. I have edited the post to reflect the correct number.

-- Gregg
 

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