How Big is too big?  

I'm 104" wide by 72" high.
Did I do something wrong?

My screen is 5' x 12'. Gain of 1.0. I sit about 15' from the screen. More info at: http://members.home.net/tvdias/

Vern Dias

Too big is when:

a) the Ft Lamberts get to below 8; and, or
b) when the subtended angle is more than 40 degrees (for a line doubled picture).



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D. Erskine
DEsign Cinema Privee
www.DEsignCinema.com
Imagine what you could do, if you could do all you imagine.

Vern,

How large is your room?
We also have a 12' x 5 1/2" screen that's located along the plane of a 16' wide wall.
We sit about 13-15' away in a 30' long HT room. Proportions are quite pleasing, and believe that images look better than when we used a 120" diagonal screen.
But we also use this screen to project film (70mm, 35mm, etc.). Widescreen rules!

The Home Theater Society

Frank, that's interesting, because Vern also projects 35mm film on his home theater screen! Have you seen Vern Dia's web page before, with the pictures of his home theater?

Do you have any pictures of your home theater?

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Thanks,
Mark Rejhon
www.marky.com

Two considerations:

1) If you have a 7" CRT, I wouldn't go any bigger than 106" diagonal, no matter what size the room. Others will push it to 120", but I think their picture suffers.

2) Don't forget your front speakers. If you place them yard or so forward and 2 feet from the side walls. you can only have a 6' wide screen. Okay, put them 1 foot from the walls. Now you can have around 8' wide. Hmmm. 106" diagonal would be perfect, wouldn't it ;-)

I've had a lot of people tell me my screen is too large (it's a 16:9 and measures 118" from side to side). I use a Sony G70.
I wanted as big a screen as I could comfortably get in my room. Afterall, I bought a FP because I wanted a big screen. And contrary to those who say it's "too big" I have not once regretted going with a screen this size. The images I get with my G70 are exceptional IMO.

Bottom line is, if you want a screen bigger than what the "experts" say you should have, at least try it first. This is a little off the subject, but this question reminds me of those who say CRT's lose 50% of their brighness after 1000 hours. Technically they may be right, but your eyes don't perceive a 50% drop - so why worry about it?

Well, TEW, with that G70,assuming a doubler, a screen of that size with a 2.0 gain, you're getting about 4.25 Ft Lamberts from the screen ... in a world where 8 is minimum, theaters are 15 to 20, and direct view sets are in the 30's. Your screen is way too big for that projector. While you're happy with it, I'd have to speculate how much happier you'd be if you tried a smaller screen for a while.

BTW, your eyes will detect differences of 10% or more.

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D. Erskine
DEsign Cinema Privee
www.DEsignCinema.com
Imagine what you could do, if you could do all you imagine.

Dennis:

I have indeed shot smaller images with my G70 and I can tell you first hand there is not that significant of a difference.
My point in a nutshell is, the increased brightness/sharpness obtain with a small screen is nominal compared to the increased cinematic experience one obtains with the larger screen. I don't think there are any devices that can measure that, and this may be what is missing from your calculations. Of course, it's subjective and up to the individual.
As someone else stated in an earlier thread, the eye perceives brightness differences in a non-linear fashion. So, measurements from devices that are linearly sensitive to brightness do not really reflect what you and I actually see. This explains why I have never been able to see the so-called 50% drop in CRT brightness after the first 1000 hours.


[This message has been edited by TEW (edited December 12, 1999).]

>I have indeed shot smaller images with my G70 and I can tell you first hand there is
>not that significant of a difference.

Did you go to the trouble of moving your projector forward and completely realigning it? Or did you simply adjust your picture to a smaller size from the same location?

Don:
For the record, the G70 is pretty bright at 240 ANSI lumens, and I use a 1.3 gain screen.

The G70 I have now is actually not mine and is therefore not permantely mounted. I did an a/b comparison of the G70 to a Plus DLP a few months ago. In order to get both images on my screen (side by side) I had to physically move the G70 closer in order to get the image small enough for the two images to be on the same screen.
Did I have the setup ISF certified? No. Did I have it converged and focused well? Yes. I have seen other set ups with smaller screens too, and I think I know what a proper ISF setup looks like on smaller screens. Of course, having a totally or near totally dark room becomes increasingly important with a larger screen. I also have very low reflective surfaces in my room.
I guess the 8 ft lamberts minimum comes from ISF folks or other knowledgable people, but if you are like me and prefer a larger screen, at least try it and decide for yourself. IMHO size does matter in home theater, and that comes from a guy who's spent most of his life trying to convience half the population that size is not all that important http://www.avsforum.com/ubb/smile.gif

I have been using a 106" diagonal screen but
on occasion I have tried using the 4:3 ratio
setting to see what the smaller image is
like. I've noticed a big difference in the
brightness, clarity/color depth of the
smaller image. The image is much better.
What's my reason for using a large screen?
Perhaps the ability/appeal to project an
image larger than what can be done with a
television maybe. I've even had people ask
can I go to a larger image size.

"What's my reason for using a large screen?"

If you have to ask that question, I have to wonder why you even own a FP. Go with a direct view TV

TEW:

I'm in your camp! Don't let anyone tell you what you like. We (wife and I) really get a kick out of our BIG screen TV. It is 120" diagonal 4:3 which makes for a very presentable 2.35 AR. I'd go larger but that is as big as my room supports. We're having fun and frankly, I don't care about the formulas for 7"CRT's. What we watch is very good looking and we're satisfied with the screen size.

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Don Landis
Home Theater Pics at:www.scubatech.com

TEW:

How far back do you sit, and what is the height off the floor, and ceiling height.

Thanks for the info.
Brian

Brian:
Seating distances range from about 12 ft to 16 or 17 ft.
The screen is about 54" tall (I think), and it is about 15" off the floor. The ceiling is standard 8' height, which is where my G70 will be mounted when I get it.
The G70 I will be using is due here tomorrow from Sony. I sent it back to Sony for new tubes. While it was there, they also replaced the motherboard and basically went through the entire unit.. Looks like I'm basically going to have a like new unit freshly refurbished by Sony. I can't wait . . . .

Chris & Don:
Glad to hear some other people are in my camp on this one.

TEW,

I have a very similar setup to yours.
And I love it.

I have a 120" wide 16:9 Draper M2500 2.5 gain screen, and a Sony 1292Q. Main seating is about 14' away.

I used to have a 120" 1.3 gain 4:3 screen which worked fine, but the vast majority of my movies are 1.85:1, and about 1/3 are 2.35:1 so the extra width provides a noticable improvement.

I have the brightness turned down to 30 and the picture looks excellent running from a PC-DVD at 1024 X 768p. I do have to turn up the brightness slightly (40) for 1080i material because it is interlaced, but it looks amazing and the brightness is more than adequate.

I have seen great picture quality from Barco 1208s, a Runco 1100, and Vidikron Vision One, with scaler/quadruplers on smaller ISF sanctioned screens. Undoubtedly they look very good, but not better to my eyes.

-Dean.

Dean:
What type of material is your 2.5 gain screen?
I used to have a 2.5 gain that was glass beaded. It was fine until my 8 year old daughter put her dirty hands on it. Glass beaded screens can't be cleaned so I had to replace it.
The 16:9 1.3 gain screen I have now is washable, but I wonder if maybe I should try a higher gain. The screen I have is a Dalite DaySnap screen, so I could replace the material without having to buy an entire new unit. What options are there other than glass beaded material?

TEW,

My screen is a Draper M2500, which is a washable material. Draper will mail you a free small sample of the material to look at, if you call them up and ask for one.

I have seen glass beaded screens, but they only seem to work well with LCD FPTVs, and can have bad hot-spooting and color shift problems with CRT FPTVs.

I had thought that my previous 120" 4:3 1.3 gain DaLite screen looked fine, and switched over to the higher gain M2500 because I had heard that it had less hotspotting issues than other high gain screens, and I wanted to go to a larger screen without overdriving the projector. But I also found out that in addition to looking brighter, both the color and contrast looked visibly better to me than the DaLite 1.3 gain screen.

-Dean.

TEW, I use the M2500 and I like it better than my homemade 1.0 gain screen!

The M2500 is washable - I can use a washcloth quite easily on it. Definitely looks better than a glass beaded screen, too!

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Thanks,
Mark Rejhon
www.marky.com