Home made projector!

[Chernobyl]

Originally Posted by Samuknow

I have two large cabinets full of hardware as well as a closet full.

Merry Christmas back at ya and again AWSOME...

nnnnggg!!
cant help it

[Chernobyl]

One piccy of Half Life 2 on the big screen before Xmas
I cant get many decent shots, my camera cant convey lower lighting levels and most pictures look too dark on camera. Anything moving is blurred too, theres a ton of those piccys!

Merry Xmas everyone.

[Chernobyl]

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

[robbie]

My buddy and I were going to make a screen. He has a projector and we need something to watch it on. For now we ended up using the side of the neighbors house!!! hahahha but.... we were thinking making a fram and stand out of wood and maybe using a **** of metal painting it bright semi gloss white. (outside viewing)
Rob

[fearless joe]

i was reading a thing from an american making a projector ages ago, he said that obviously a pre-bought screen is the best, but that the silver reflective surface on them was paint that you could buy of the shelf, i cant find it now, but if its true it would be perfict
joe

[danrok]

I used to make projection screens for stage sets. We used to get front and rear projection material from Rosco, they make all the best stuff!

http://www.rosco.com/uk/index.asp

[danrok]

This a method we devised to make a screen.

Using Speedframe 25mm square tubing from Dexion. http://www.dexion-anglia.co.uk/shelving.html

Cut the tubing to size and use four L shaped Speedframe connectors to join the lengths together.

Put hook velcro along the steel tube on one side completely covering it. Use a seam roller to make sure the velcro sticks.

Cut the screen material to size and put loop velcro all the way round it's edge.

Attach the material to the frame. If there are any creases just peel the velcro off in that area, pull tight and plonk it back on. The velcro and tube is 25mm wide so you have 50mm of play for adjusting the tension on the material.

The whole thing can be taken apart and stored if need be.

[Samuknow]

I can give you a little insight from past experience. I have used projectors, mainly for presentation pourposes, and I can tell you that there is a huge difference between "homemade" and other purchased screens. Even using a WhiteBoard, dry erase board, is not even close to the quality you can obtain from a screen designed for projectors. some have a slightly textured surface to keep the light from reflecting all over the place and direct it back to the viewing area. If you truly want the best image, I would look at Ebay and see if you can come up with a screen that will fit your budget. I don't think you will be dissapointed.

[Staz]

I don't know how you feel about it but.....

If you want to display right on your wall, 1/4" drywall is very cheap. It can be attached directly to the wood paneling with #6 x 1" drywall screws. It also can be finished off by almost anyone, it just takes alot of time and a lot of dust is produced. Drywall mud is very forgiving.

Then you could paint it any color that would give the best results and you wouldn't have to worry about light bleeding through the back of the screen.

[danrok]

A custom-made fixed screen of some description is better than a roller type screen which tend to curl, move around, etc.

[Samuknow]

Link

Here is a link that might help you

[DiabloAbogado]

Originally Posted by danrok

A custom-made fixed screen of some description is better than a roller type screen which tend to curl, move around, etc.

I agree, but some people might not have the huge space to take over a wall and leave it bare. I was thinking about mounting a pull down screen to the ceiling that you just pull down when you need it (ie gaming, movies) and can roll up when you don't need it or company is over. Although cost is more of a factor for something like this, instead of painting a board white.

[danrok]

It's all down to what suits you, what space you have available, lighting, etc.

Another thing to consider for a fixed screen is that you can use a perforated screen material which allows you to place your center speaker behind the screen - same as in a cinema.

[Chernobyl]

Wow,
thanks for all the replies, theres some excellent information and links.

The P100 203 x 152 Theatre screen (100" diagonal), £138 has me thinking hard if I can cope with a slight curl. I could weight the ends down?
http://www.projected.co.uk/screens/wall-screens.htm
Thanks for the link Samuknow, good info too.
It has a gain of 1.2 which is pretty good especially for the convenience.

The Screen needs to drop down in front of the telly and ideally be portable, so the above fits the bill right on.
There is another non portable option. I can hinge a screen from the roof. It would need to slide back a little too to avoid the lights, but its certainly an option.

Price is a prime concern as I have none now
The price of the frame/board, fittings, proper paints and coatings for a permanent screen is not far off the pull down screen, without the convenience.

Does anyone know what gain I can hope to get if I use a well prepared painted + coated screen?

cheers

[Staz]

I'm not sure about the gain you would achieve, it would depend on the coatings and or screen. I followed the links from Sam and Danrok and found screen materials with all diferent atributes and gains from 1 to 2.8 which were suitible for diferent viewing circumstances. But I did not find any paint on coatings.

I have read the whole thread and have a couple of questions:

1. How big is a 15" LCD screen? just curious as to what dimensions the lighted table on the overhead projector?

2. Once everything is mounted how hard is it to change the bulb in the OHP?

3. You say that on the sheet you could only get an 8' image because after that the image gets 2 dimm, do you think that if you had a proper screen or even just a painted wall that you could expand the image to 10' or more?

4. From your experiance, do you think it would be feasible to build one of these the build a acbinet for it and suspend it from the ceiling? What are the approximat dimensions of your completed unit?

[fearless joe]

i can only answer one of the questions really, as i havent built mine yet,
Have you ever picked up a ohp, they are very, very heavy, it is concivable that you could hang it of a celing or wall, but it would have to be a substantil build,,,,,unless, if you get one of those tiny ohps, with the light at the top, there no were near as heavy, but there dam expensive, espeasally as there never normally as powerfull as the big ones, hope this helps
joe

[Chernobyl]

Originally Posted by Staz

I'm not sure about the gain you would achieve, it would depend on the coatings and or screen. I followed the links from Sam and Danrok and found screen materials with all diferent atributes and gains from 1 to 2.8 which were suitible for diferent viewing circumstances. But I did not find any paint on coatings.

I have read the whole thread and have a couple of questions:

1. How big is a 15" LCD screen? just curious as to what dimensions the lighted table on the overhead projector?

2. Once everything is mounted how hard is it to change the bulb in the OHP?

3. You say that on the sheet you could only get an 8' image because after that the image gets 2 dimm, do you think that if you had a proper screen or even just a painted wall that you could expand the image to 10' or more?

4. From your experiance, do you think it would be feasible to build one of these the build a acbinet for it and suspend it from the ceiling? What are the approximat dimensions of your completed unit?

Hi Staz
1) I decided to draw a picture of the OHP glass shape/size, its not quite to scale and should look like a square not rectangle. Please see attached
In reality this translates to losing a bit of the right and/or left side of the screen. The top and bottom fit easily. The LCD panels size is 12.1" x 9.1"
Some games are tricky on the big screen if the bottom corners of the screen hold information you cannot move elsewhere.

2) It may depend on the OHP. I have to remove the LCD to open mine. its real easy though, takes 10 seconds in its current state. Changing the bulb is very easy on this model.

3) Its tough to extrapolate without a wealth of experience. A high gain screen should have no problem (gain 2 or more) getting the size you want. The screen I will be using will most likely have a gain of 1.2-1.3, ~double that of the bed sheet. I'm hoping a 9ft screen is possible but will be happy with 8ft.
Its touch and go whether the size screen you would like would work with a bright painted wall. Choose the paints welll!
Ambient light should be kept to a minimum for that size screen.
(You can use a more powerful OHP, mine is 400W, 4000-4500 Lumens)

4) Roof beams should certainly be able to hold the weight, mount it well. It will need to be upside down as the reflector mirror needs to be near the centre of the screen.
There are some issues to deal with:

a) As the OHP mirror needs to be central to the screen, you may need to put your screen higher up and mount the OHP some distance from the roof. If you have a high roof things may get trickier.

b) heat will pool a bit around the bulb area and just above unless care is taken to shift the air. On mine, the standard fan simply draws air out, there is nothing to circulate the air inside the OHP much. Too much heat means less bulb life. They reach 500C !!
I imagine there is no fan blowing onto the bulb for a reason, it may be wise to not do that directly.

c) the LCD and its cooling needs to be sturdy and removeable as you have surmised. I would make a frame structure to mount the LCD bits + fan(s) in, that is easily moved and secured.

My Projector isn't finished so I cant give dimensions of the finished product.
I can tell you the size of the OHP as its sat here.
15.5" x 14.75" x 32" (depth x width x height)
the height is to the tip of the mirror which can move further, the other dimensions include bits that stick out.
I have the OHP raised 23" off the floor too.

[Staz]

Originally Posted by Chernobyl

Hi Staz
1)
In reality this translates to losing a bit of the right and/or left side of the screen. The top and bottom fit easily. The LCD panels size is 12.1" x 9.1"

4) Roof beams should certainly be able to hold the weight, mount it well. It will need to be upside down as the reflector mirror needs to be near the centre of the screen.
There are some issues to deal with:

a) As the OHP mirror needs to be central to the screen, you may need to put your screen higher up and mount the OHP some distance from the roof.


My Projector isn't finished so I cant give dimensions of the finished product.
I can tell you the size of the OHP as its sat here.
15.5" x 14.75" x 32" (depth x width x height)
the height is to the tip of the mirror which can move further, the other dimensions include bits that stick out.
I have the OHP raised 23" off the floor too.

Thnx for the info

So it is important to find a projector with the largest screen size availible. I asked because I looked for projectors and found diferent size screens

As for the position of the mirror, I had envisioned building it upside down. But to achieve a 10' screen that would mean having the mirror at a hight of about 5 1/2' from the floor. What happens if the mirror is higher or lower than that? I assume that the picture would become trapizoidal, but how trapizoidal? and could it be adjuested for useing the trapiziod adjustment on the monitor? (I can't believe I just typed that! Of course it can't, LCDs don't have a trapizoid adjustment, only CRTs do, but I'll leave that in just incase someone else has the same brain fart I just did.) OK, so how trapiziodal does it get?. You could demonsrtaight this taking a pic of the setup in its normal mode (you have already posted many of thoose) and then setting the projector on the floor and leaving the screen hieght the same and taking a picture of that.

[Chernobyl]

Originally Posted by Staz

Thnx for the info

So it is important to find a projector with the largest screen size availible. I asked because I looked for projectors and found diferent size screens

As for the position of the mirror, I had envisioned building it upside down. But to achieve a 10' screen that would mean having the mirror at a hight of about 5 1/2' from the floor. What happens if the mirror is higher or lower than that? I assume that the picture would become trapizoidal, but how trapizoidal? and could it be adjuested for useing the trapiziod adjustment on the monitor? (I can't believe I just typed that! Of course it can't, LCDs don't have a trapizoid adjustment, only CRTs do, but I'll leave that in just incase someone else has the same brain fart I just did.) OK, so how trapiziodal does it get?. You could demonsrtaight this taking a pic of the setup in its normal mode (you have already posted many of thoose) and then setting the projector on the floor and leaving the screen hieght the same and taking a picture of that.

lol

With the projector sat on the floor I took the attached pictures. First 2, the height of the projected image is the same as all earlier photos, bottom of the screen is 23" off the floor. The 3rd image is 1 to 2" from the floor at the bottom. Its not bad!! In fact I really like.
Looks like I will need to make the new screen height adjustable so it drops to the floor.


I have just confirmed that better cooling of the LCD is needed.
When the OHP/LCD are first turned on, the picture is pretty bright. After 1/2 hr it goes a bit yellow even though its cold to the touch. I will investigate this further.
Incidentally, every photo taken so far has been using the OHP in low power mode. There is a minute improvement in brightness on high power, it really is tiny and costs 1/3rd of the bulbs potential life and produces more heat.

edit:
the game is Rome - Total War

[Gizmo]

Originally Posted by Chernobyl

b) heat will pool a bit around the bulb area and just above unless care is taken to shift the air. On mine, the standard fan simply draws air out, there is nothing to circulate the air inside the OHP much. Too much heat means less bulb life. They reach 500C !!
I imagine there is no fan blowing onto the bulb for a reason, it may be wise to not do that directly.

You can blow air directly on the bulb to help cool it and extend the bulb life, but you have to be very, VERY careful. Reason being, as hot as that glass envelope gets, you can create enough of a temperature differential to shatter the bulb. This means that great care must be taken in ensuring that you have even airflow across all of the bulb. As this is very hard to ensure, most of the less expensive designs don't even try.