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Old 21st January, 2005, 06:41 AM
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Chernobyl Chernobyl is offline
Projector Wizard
Join Date: November 2004
Location: UK
Posts: 594

A quick note before I write about my latest discoveries.
Using the information in this thread and other things found, I will eventually create a full decription how to make your own projector system cheaply and as easily as possible. Some of the details involved in getting there are technical and required to make the best decisions during my investigation. Its easy to accidentally choose parts which will not make you happy with the end product.
I will cover the essentials after the project is finished to make it easy for you to decide if what you are buying is suitable. I will also cover how to fit any new parts and the issues involved. This will no doubt restrict the types of some components, I will try and give a gauge how badly a 'wrong' component will affect the projector too should you come across some parts cheap or free.
Dont let the detail being exposed here put you off trying to make your own projector!

The results I have with a very wrong bulb (3400K) are extremely impressive.
The bulb I have has a weak blue output. Blue has a mild yellow tint to it and white is mild yellow. Reds, yellows and oranges look stunning! Changing the bulb to a full light spectrum centering around approx 5200K white light will bring all the colours into balance including white. These bulbs are very cheap, way cheaper to run than the current bulb I am using which is approx half the running cost of a purchased projector.
In my view, changing the bulb will nearly perfect making a top notch projector at 1024x768 res!

The only problem left is the loss of about 1/15 to 1/30 of the pictures side. Its a minor issue and I can certainly live with it.
Screen definition, resolution, speed and size are superb.
The screen is 5ft diagonal now which to be honest is perfect for watching TV.
I hope to make it scale to 80"+ for films and gaming with a new very bright Metal Halide bulb.

It should be easy to allow the screen size to be varied.
With a powerful bulb, it may be too bright with a smaller display. Metal Halide bulbs cannot adjust their brightness (not for the price we are paying!) but a filter to dim the light output of the projector can be used instead.

At any time if you consider anything I have said needs correcting, please feel free to discuss it here. There have been a few times during the project where I have wandered down the wrong path and tried to draw conclusions without a full barrel of knowledge. Theres certainly a lot to cover and more to go.

Onto the game!
As well as the Colour Temperature of a bulb, there is another indicator of colour on many bulb sales sites called CRI (Colour Rendering Index). This has been found to be vital when considering the best bulb for the projector.
Here is a pretty good description of CRI and the Colour Temperature:

The CRI takes 8 points on the light colour spectrum and uses the colour of lit objects at those colours to give you a CRI value of the bulb. The higher the CRI, the more natural objects will look when they are lit by that light.

A CRI of 100 is perfect.
A CRI of 80 is considered very good. Values below that can affect your colours in unknown ways, but values below 80 may still be acceptable. I will find out.
High CRI values on a wrong Colour Temperature bulb will not make it work well on your projector.
Once you know the colour temperature (5000K to 5600K), the bulb is then chosen which is/has the right type, size, fitting, shape, power, CRI, cost and availability. There may be more to add to the list, thats my knowledge so far

Choosing a bulb with a high CRI is very hard when browsing online as most websites dont display the CRI value. Many dont tell you the colour temp either. I will find out soon how helpful shops are at finding the right bulb.
More to come.
2.9m DIY home made LCD PC projector !
Venice 3000+ (1.8GHz) @ 2.7GHz, 1.4V
Stock air cooler
X1800XT clocked to PE
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