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Discussion Starter · #1 ·
Hi guys

I'm considering a new projector for my HT room. I intend to have a 16:9 screen of size around 90-110", and I want to ceiling mount my projector. My HT room is currently under renovation, and they need to know where the projector will be, so I have to know the distance from my screen.


The problem is, I don't know which projector I'm gonna get. It'd be good if the projector has some sort of zoom, so that it doesn't matter if my distance isn't that accurate, but I'm also considering the NEC LT150, which doesn't have any zoom at all, so I have to know the exact location. projectorcentral.com only has throw distance calculations for a 4:3 screen, so I'm wondering how I can calculate my throw distance for a 16:9 screen.


Some of my projector choices are the NEC LT150/155, VT540, Sanyo PLV-60 and Sony PLC-VW10HT or 11HT if its good.


Also, another problem I have will be ambient light, since my HT room will be on the top floor, with a few large windows on the walls and rooftops for sunlight to enter. Even with curtains, I foresee that the ambient light will be quite bright, so I'm wondering if the LT150, with its 800 lumens output, will suffice?
 

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Well said, Dave.


The same information can be expressed as:


The throw distance for a 16x9 screen of a given diagonal would be 9% less than for a 4x3 screen of the same diagonal.


-yogaman
 

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Discussion Starter · #5 ·
Thanks guys, any comments/opinions on my choice of projectors given my situation? I will probably be using a HTPC to view my DVDs. Is it advisable to use a high gain screen(gain of 3 or even 4) for a weaker projector such as the LT150?
 

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I can't talk from personal experience about how the lt150 would look with some ambient light, with a screen of that size. But, I would say that you should do everything within reason to cut down on the ambient light. Black out curtains do an excellent job, and you could even get shades for your skylights. WRT the screen gain thing, one thing to keep in mind is that higher gain screens look worse with off-axis viewing, so you have to make sure they'd work with your seating arrangement. If you could see the projectors you're looking at demo'd with some different screens, that would be best, but I know that's rarely an option...


- Dave
 

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Before going to a real high gain screen, I'd suggest getting a PJ with more lumens, like the PLV60. For me, gain of 1.8 is fine, 2.3 is pushing it, and 2.8 is too much. With more lumens, you could go to a grey screen with 2.3 gain (I think DaLite has one) and get a decent picture with moderate light control.



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Steve
 

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Goi:


Check out Widescreen Review magazine vol.10, number 4, issue 48 May 2001, p.41. In it they're reviewing a Vidikron LCD pj but more importantly, they have a formula for addressing your brightness question.


Screen brightness (ft-L) = lumens x screen gain/ screen area (sq. ft.)


In the article they suggest that the average movie theatre brightness (in a totally dark environment) is 10-15 ft-L . . .If you want to view images with a moderate amount of room light and to have a really high impact image, you need 50-100 ft Lamberts (ft-L). So, you're looking at a pj with a minimum of 1200 ansi lumens+. . .also would suggest a slightly higher gain screen (not "Grayhawk" w/ 0.95 gain, you need at least 2-2.5 gain) plus limit screen size to not greater than 100" diagonal. Play with the numbers. . . substituting lumens of various pj's to get your best overall score.


Obviously, brightness isn't the only requisite for a great picture, so you'll also have to search for a projector with decent contrast ratios(at least 500:1, higher is better). I suggest you go to your local library or Borders and check out that article.
 

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I think there's a little more to it, when comparing a high gain screen to a greyhawk. You can try to "overpower" the ambient light in the room with a brighter projector, and/or a higher gain screen. But, the grayhawk has some unique properties that allow it to reject off-axis ambient light. So, even though the foot-lamberts calculation derives a lower number with the greyhawk, it can still give more contrast than a higher gain screen. Check out this thread.
 

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I hope this is not too far off topic:


I am trying to understand the origin of the Grayhawk's reported ability to reject ambient light.


I see this ability stated in numerous posts, very often from owners of Grayhawk screeens. However, other than mentioning a "translucent coating" or "silver/pearlescent-like paint splattered" over the gray substrate, I don't see much description of what the material is or what its special properties are.


I doubt that all these glowing (no pun intended) reports arise from some kind of mass hysteria, but I am trying to assure myself that there is a measurable effect at work.


Can someone please post a reference for what makes the coating (or other screen properties) so effective?


-yogaman
 

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Goi,


Here is the formula for LT150 (and all U3-1080 clones):


for 16:9 screens -

Screen width = 1,457 x diagonal


for 4:3 screens -

Screen width = 1,338 x diagonal


Before ordering the screen try your projector first on the white wall ,

you'll see what size is right for you. Anamorfic 2.35:1 movies looks smaller on 16:9 screens and even

smaller on 4:3 screens.


Alex

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You'll definately want to control that ambient light. Any kind of sunlight hitting the screen directly or bouncing around the room will wash out the image where it hits, be it diffused or filtered by whatever window coverings you choose. Plus, it'll move slowly as the sun shifts during your viewing session. Blackout curtain fabric or pull-down shades are a must (IMHO) to control outside light. As far as inside lights, dimmer-controlled cans or reading lights or even ropelight can be installed around the room to give some ambient light that won't wash out the image.


As far as throw distances, most projector manuf. have online PDFs of their owners manuals that will let you see which screen size to throw ratios you'll see. But I wouldn't wire and drywall the room until you have your projector AND screen size (you can tape it off on the wall)figured out, so you know where to put your J-Boxes.


I have a VT540 and love it (except for dust blobs... see my recent post), but I hesitate to recommend a specific projector becuase the VT540 is the only one of demoed in its price range. Whatever you get, I'd get one with a zoom lens to make minute adjustments to picture size for all the different aspect ratios you'll use.


My $0.02 anyways,

Brian
 

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Discussion Starter · #13 ·
Thanks for all the info guys, appreciate it. Unfortunately, I'm stuck with my current situation of ambient light. I'll probably look into blinds or curtains or something. As for the projector, I'm not too sure. The prices of the better performing projectors(PLV-60, PLC-XP21N, etc) are putting me off a bit, so if its possible, I'd like to get by with the LT150, since its currently so cheap! I guess I'll check the projectors out and see how it goes, thanks again!
 
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