I've done a fair bit if research on screens and have dug up some interesting stuff.
For a quick test I put some brilliant white printer paper on the screen to see how much brighter it would be.
The 2 closeup photos are of Lord of The Rings and Winamps Milkdrop.
(I edited the LOTR photo to look more like my screen as the camera over saturated the colour, the effect can be still seen)
It seems the paper will give somewhere near a 1:1 ratio of light back to the eye (A gain of 1). From research, this means the light received at the eye is the same level as it was sent to the screen. (I dont quite believe the definition as the ratio goes above 1! It does serve as a good figure to compare brightness though.)
The gain of the sheet must be much less than 1 as you can see.
Why is a sheet so bad?
A lot of light passes through a sheet, giving 2 bad effects. It makes the area behind the projector lighter, illuminating the screen slightly, reducing contrast. That light is also not reflected to they eye where it should be.
To fix this, the sheet could be mounted on a large board that is painted black, white, grey or silver. Theres quite a few arguments for the use of each colour. The sheet wouldnt be the best reflective surface still.
I looked at using a brightener on the sheet as they are readily available quite cheaply. I was informed that it would last 4 weeks. Not promising.
If moving to a board, I can dispense with the sheet altogether and paint the screen directly onto the board without the previous ill effects.
A well prepared wall is also an excellent screen. (Mine are wood and bumpy, not so excellent)
There is some nice looking material on ebay in the US (search for screen material) that can be stretched many times over a frame. This has a gain of 1.3 and is a bargain for the price/size if it works as advertised. Judging by the number of happy customers, its a fair bet.
Also heavily discussed is a material called PolyWall or Plas-Tex and seems to be only available in the US. The product is advertised as either name, but you must make sure what you are getting is the PolyWall Bright White (more on that later).
This material is semi rigid plastic and if shipped comes on a roll. It keeps the shape of the roll a little so needs leaving flat for a few days before using. If it is warped it will be replaced for free. The Price is about $60 for 10x5ft (so I've read).
At has a gain of around 1, theres a fair bit of speculation on this, but it seems to be 1 or just over. Its washable and withstands scratching very well, but not holes (dont burst air bubbles with a pin!).
The 2 sides are different, one is semi glossy, the other is textured matte. Most users seem to prefer the matte side as it reduces hotspotting on some projectors. The Glossy side is reported to be brighter but at the cost of maybe seeing bright spots from your lamp.
This sheeting must be glued onto a solid back board as it sags over time.
It seems I'm back to the board again!
A bit of background:
There are 3 main types of projector that I have found discussed.
CRT, DLP and LCD.
CRT uses 3 LCDs one for each colour (RGB or CMY) and combines them for a single quality image. Not so bright for the same lamp power, very good quality.
DLP makes use of mirrors to direct light on to the screen and is less lossy and gives good image quality.
LCD is the method I am using. You would think from the above that it wouldnt be very good, I'm in awe so far! I hope to do some comparisons over time to see the difference.
The system I have built so far shows extreme promise but its potential cannot be realised with this sheet as a screen. Many of the colour etc adjustments I have made will no longer be necessary and setting up Windows to play everything well will be so much easier.
As it is, everything is playable/watchable, but for some films you really need a dark room to catch the fine detail.
CRT machines like a bright screen as the light source is split through 3 LCDs before it reaches the screen.
DLP machiines seem to be of 2 broad types, one produces better blacks. The better black version can use many screens/paints and work very well. The other type seems to work better on a slightly grey screen which makes black appear darker, enhancing the contrast ratio. The light grey Polywall might be a better option than bright white, but I have found nothing to confirm it.
LCDs prefer a bright screen. From older discussions in year 2001, 90% of light was absorbed by the panels then. By Observation, the LCD I have is not as bad. I would say it forwards 20% of the light. Without a meter though, this is meaningless, but hey, its an opinion
In a dark wooden walled room during the day with the curtains closed, it operates extremely well with everything except very dark material.
I hope to make it very good for day use and excellent at night by improving the screen.
There is a lot of discussion on colours, silvers and glass bead type paints/materials. The highest gain material is glass beads, some claiming a gain of 3 ! There are some paints which appear to have these mixed in. There are also screen coatings which can be sprayed/painted on to give a similar effect. One mentioned often is ScreenGoo.
The paints can be mixed or applied in different layers to achieve good effect.
For example some older DLP projectors which dont handle black so well can have the screen painted first with grey/silver and then coated lightly with brilliant white. This enhances black while retaining a high reflectivity.
Walls or wooden boards appear to be popular. The surfaces must be properly prepared so no shadows or bumps are seen (after painting) and light levels remain consistent over the screen area. For a wooden board, this means it is ideally in one piece as a join will nearly always show.
I wish to either get the screen material off ebay and build a frame or get a big piece of board , paint it with bright white paint and put some screen enhancer on it. I'm sure either would be excellent.
choices