[GreggPenn]

In one of Tryg's screen reviews, the statement is made that there are two basic types of screen materials -- angular-reflective and retro-reflective. The Firehawk material is listed by him as a retro-reflective material.


When shopping for a screen, SilverScreens (Stewart dealer on this forum) recommends the Firehawk for the Sony HS20. And, it is recommended for ceiling mount. This seems to contradict the recommended use of a projector that is retro-reflective. Normally, I thought you should mount a projector firing on a retro-reflective screen nearer head level.


O.K. I can understand where this would still work as long as the viewer and projector are still considered within the main viewing cone. But still I have to wonder....


Also, after shopping for less expensive alternatives, I investigated the Da-lite HCCV. I gather that many would consider this to be Firehawk's main competitor. When I emailed a Da-lite dealer to inquire about various characteristics of this screen, I asked about mounting configurations. Again, I learned this screen is O.K. for use with a ceiling mount. However, when I asked if the screen was angular- or retro-reflective, they replied that is was scatter-reflective. The salesman went on to say the this screen shared properties of both screens. And, that is reflected light in many directions -- hence the scatter-reflective categorization.


Is this a new screen type that should be added to the list? Why doesn't the Firehawk story quite make sense? Since we let Tryg's screen reviews serve as a screen "bible", are enough of the necessary facts present and accounted for in these reviews?


gp


(I am not trying to start a flame war, but since so many people are referred to these reviews, it seems necessary to be as complete and accurate as possible).

 

[Jason Turk]

I didn't read that review fully so I can't be sure why he wrote that. However, the Firehawk is an angular reflective screen. That is why they recommend it for ceiling mount situations. The HCCV is also angular reflective and is a good alternative to the Stewart, especially if cost is a concern.

 

[Michael Grant]

Gregg, that's an error in Tryg's review. The Firehawk is an angular reflective screen.

 

[akm3]

And my new firehawk comes from Jason tomorrow I'm so excited.

 

[Tryg]

Greg and others...


sorry, which review and where and I'll fix it. sometimes i get a little excited when I type and try to use my brain at the same time


Firehawk is angular reflective!


Although I think they use a retrorefective substance on the surface(i could be wrong about this), the predominant behavior of the complete screen is angular reflective.

 

[GreggPenn]

In the High-gain/Exotic review (post #1), the following paragraph appears:


-------------------------------------------------------------
Retro-reflective This is like a stop sign and other traffic related reflecting devices. The light is reflected back toward the source. The following screens in this review I found to have these properties were:


Da-Lite Hi Power, Da- Lite Glass Bead, Stewart Filmscreen Firehawk, and the Stewart Retro Grey (experimental).

-------------------------------------------------------------


This is in your discussion about the fact that there are two basic screentypes. Thanks for the clarification on the Firehawk. However, you didn't totally address my question about "scatter reflective" screens as defined by the Da-lite representative. Is scatter reflective a type of angular reflectivity where reflections are just more "diffused"?


gp

 

[Michael Grant]

A perfect 1.0 gain matte white screen is neither angular reflective nor retro-reflective---any light that hits it is sent out in all directions equally. The geeky term for it is a perfect Lambertian reflector. I wonder if that's what the Da-Lite rep was talking about.

 

[Tryg]

I've taken it out of the review so it doesn't confuse anyone.


The components of a screen can have different properties. You would descibe the screen as having the most of the properties summed.


A matte white screen is angular reflective. As shown by the fact that there is a viewing cone. No screen has perfect uniformity from 0 - 180 degrees. It does diffuse the light so well in most all directions though it's mute point.


to prove this just shine a spotlight at the screen from 45 degrees. A spot meter will have a higher reading on the opposite side to where the light is bouncing

 

[GreggPenn]

While on the subject of the Firehawk's reflective properties, please answer one additional question if you can.


On my white latex wall, I could use the focus grid of the Sony VPL-HS20 to acheive perfect focus. I displayed the grid and focused until sharply defined pixels appeared which created the word "FOCUS".


When I saw the HS20 on a Firehawk (at someone else's house), this focus technique was somewhat more difficult. That's because it didn't seem like I could get clear edges on the pixels. Had I been thinking, I would have held white paper in front of the screen (while focusing) to determine if the Firehawk does something to the clarity. (FYI: This did not seem to affect overall image clarity).


Did the reflective coating on the Firehawk (light scattering?) cause this effect? Or is it more likely that the second machine just could not focus as clearly?


gp

 

[Michael Grant]

There's a reason I said "perfect" matte white screen, Tryg. Still I think you'd be surprised how close practical matte white screens come. Stewart doesn't even like to sell them though for home theater applications because they spread the projected light out so widely that too much of it hits the walls & ceiling.


Also, there's an interesting contradiction in the science of reflections. A screen which reflects light in all directions equally still obeys a "cosine" law principle: the brightness falls off as the cosine of the viewing angle. And yet, the screen still looks just as bright from all viewing angles, because a viewing angle compresses the screen in our field of view. Here's an interesting article that helps to tease out this apparent paradox:

http://www.fordav.com/publications/cb20.pdf

 

[GreggPenn]

Does "perfect" matte white screen apply at all to my question two posts back?


(O.K., I know it doesn't relate to your post, but it was a nice segway back to my question)!

 

[Michael Grant]

I don't know... I don't know what could be the cause of what you saw...