Optimum projector / screen distance ?

[JezHill]

I'm currently building a house with a 6m long cinema / kids playroom.
The room is currently being wired and I'm trying to find out optimum distance from a ceiling mounted projector to the screen.

I've googled it, but would appreciate any advice from you guys.

Problem is I dont know which projector I will go for until I know how much money is left in the kitty nearer the end of the build. Also the screen could be 6' to 9'

[PJ S]

Projector requirement will be dependant upon ambient light, distance/size of image, and budget - not to mention screen type.
Whilst it's all well and good throwing up a graph of distance vs diagonal screen size, this needs to be tied in with the lumens output of the projector you can afford, in relation to the screens reflectance value, and if you want to sit in low light or complete darkness, when using it.

[Saintjsmythe]

You really need to know the projector and screen make and model/size then call the projector manufacturer with the screen dims and the will calculate the distance for you. Its really worth doing correctly and this is the best way.

[OldSkoolRS]

If the projector is going to be the full 6 metres away at the back of the room, then it will be hard (even impossible) to have a screen as small as 6'. I have my JVC HD350 at nearly 6 metres from the screen and the image is around 100" diagonal at minimum zoom for example. I also use an Anamorphic lens which further increases the width of the image by a factor of 1.33 so I had to select a screen nearly 10 foot wide to suit.

Benefits from using the projector at minimum zoom like I do, means that you tend to get less distortion from the projector's lens (it's using a smaller area of the lens) and also to get maximum contrast from the projector (min zoom= max contrast, vs max zoom = min contrast due to some technical reason I can't remember off hand...F stop or apertures, something like). The negative is that the brightness is the opposite case to the zoom/contrast situation, so I get least brightness at min zoom, hence I choose a screen with a little gain.

Like a lot of AV setups it will pay to get advice from a good dealer, or be prepared for a lot of research and some mistakes along the way if you DIY...I know as I've been there.

[LandingSpot]

How wide is the room? Are you planning to put speakers either side? Will you have an acoustically transparent screen? This would mean you could have a bigger image overall (throw ratio, budget and available space dependent).

The "recommended seating distance" is supposed to be 3x the height of the screen. You can go either way of this but then start gradually moving toward the image being too big to be able to view it comfortably.

So a room depth of 6m would give an approximate fiewing distance of 3-5m (with room at the back for speakers etc).

A 4m average viewing distance gives a recommended height of 1333mm giving a 16:9 width of 2370mm and 2.35:1 width of 3133mm.

You will then need a projector with a throw ratio of 1.5 - 2.32:1 (and associated 1.33x anamorphic lens). You will also need at least 40% lens shift as having the PJ ceiling mounted will mean the image has to point down and you DO NOT want key stone correction.

The next thing to consider as mentioned above is the light output of the PJ. You need to know this so that you can get a complimenting screen. You don't want a high gain screen if the PJ outputs enough light to be bright enough on a 1.0 gain screen as it will be offensivly bright and have a nice hot spot in the middle of the screen which is undesireable.

Hope this helps

• ETA I would put the PJ as high up the priority list as you can since it is something you will see everytime you use it. People spend heaps on their telly because you see a visible difference whereas spending the same on audio is not necessarily because it is not so easy to hear the performance differences.

The light output will decrease over the lamps life and you don't want to spend half your time watching a dull picture.

Edited by LandingSpot on Wednesday 14th April 19:35

[LandingSpot]

Forgot to say that all of these dimensions change if you alter one. i.e. your throw ratio may (probably) change if you change where you want to put the projector or the screen width. You should generally start with one of to measurements; your desired screen width of a specified aspect ratio or the distance between the lens and the surface of the screen.

[cjs]

As a very rough guide, most projectors have a throw distance of around 2x the screen width, so a 6' wide screen would need the projector sitting back 12'. Obviously the proj will have a zoom function to compensate. But, as already said, you really need to know your screen size and the projector spec you are going to use.

[JezHill]

Thanks for the info guys, thought it would complicated so I am glad I checked.

Lots for me to look into before the ceiling is plasterboarded then!