Film-Tech Forum ARCHIVE: DIY Projector

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Posted by Peter Berrett (Member # 672) on 06-26-2006, 07:38 AM:

Hi all

Following on from the thread about 16mm, this made me think about a project I did a year or so ago.

I speak of course of a DIY projector using a lcd panel + an overhead projector.

I was interested to see what results could be achieved with a modest setup. I purchased a second hand overhead projector and then purchased a second hand InFocus PanelBook 550 LCD Screen. Total cost was about $A400 including postage for the panelbook from the US.

Here's what an Infocus Panelbook 550 looks like

http://realm-online.com/epanelbook.htm

According to this site

http://www.diyprojectorcompany.com/theory/lcd.php

the specs are

Native resolution 640 x 480
Colors supported 1.4-2.1 million

I used with both my dvd player and with my satellite tv setup. I put in in my bedroom and used it to project an image about 1m square on my wall

It gave quite a bright clear picture and was quite watchable however there were a few drawbacks that are not easily noticeable from the sample picture you see scattered around by people who build these things.

The first is the overhead projector. The fans in these are noisy and distract from the viewing pleasure. Maybe one could build a special box to quieten everything down or get a quieter overhead projector but it is a definite drawback.

The next point is less obvious. Because the projector setup is reasonably large it has to sit on a table which means that you have to view the picture from an angle. I like to sit in the sweet spot - ie centre to picture so this is not ideal. One could in a bigger room put the projector up higher (perhaps in a special booth) and then sit down in front of it but it would require some extra room. This is where new lcd projectors with their small size come into their own. They can be ceiling or wall mounted which lessens space requiremnts.

The next problem, alhough not too severe was a tendency for the screen to be a bit too dark at times - this may be what they call contrast ratio? I found that I could get better contrast by winding up the brightness but then the whites seemed to flare a bit. One could still get a reasonable balance however.

Finally the major problem for me was the color.

The following is a link to a review of a DIY project. On the page is a video which is worth a look if you have broadband.

http://www.denguru.com/2004/12/01/build_your_own_xga_projector_ii/page6.html

My results were similar although the picture was a little smaller. The main problem I found was that the lcd panel didn't give a true color reproduction as a tv set or a monitor would. The reds and blues had a kind of metallic look - like the reds you would expect to see on mars or the blue paint on a car. You don't tend to see true pink and yellow was a little muted. Resolution was very acceptable however.

I have since sold my setup and unfortunately have not taken photos of the results but I would be keen to try again one day if a suitable tft screen or lcd panel could be found. The color reproduction results obtained in the link above were similar to the results I achieved although my setup had slightly worse problems with darker movies.

In a way the color reproduction of lcd panels reminds me of how films shot on Eastman color stock in the 70s went pink. With filters you could make the film acceptable to watch but the colors were never quite right. Ditto for my lcd panel.

When I go into electronic stores all the lcd projectors seem to be playing animated films thus not giving me the opportunity to see whether they can more faithfully reproduce natural colors. Has lcd technology advanced to the point of being able to give more natural colors? If so would a late model tft screen used with a quiet overhead projector give better results?

My mother-in law recently purchased an lcd tv and hung it on her ewall (it's a 17" model) but I find the picture hard to watch - again the colors appear metallic and hard - there is no softness to the picture.

I am interested to put my learning into some context. Could someone learned (cue My Pytlak) please step in and explain what I have experienced?

ps even though the project didn't yield great results it was a lot of fun putting it together and trying it out!

Thanks Peter

Posted by Cameron Glendinning (Member # 3516) on 06-26-2006, 09:33 AM:

I believe there are several issues that could change color
The color temp of overhead projector bulb
Polorizing filter on the LCD panel, some people actually peel it off. Anyway image looks different from different angles, ie darker from below, brighter from above. So play with panel angle ect.
LCD panels for this purpose need fast refresh times 4-8 miliseconds are best.
The projectors are huge!!!!!!!!!!!!!!!!!
I personally wont be tring this [Razz]

Posted by Charles Greenlee (Member # 3856) on 06-29-2006, 01:14 AM:

Wow, I remember those from school. They had them for the TI calcuators. And the Apple II's had a few lcd units designed to fit on an overhead projector. Anyhow, sounds like something just fun to mess with, if I had the money. Wouldn't expect too much out of it, but fun to tinker with, nonetheless

Posted by Brad Miller (Member # 2) on 06-29-2006, 01:40 AM:

Peter - please stop posting home video stuff here. Keep it in the afterlife forum where it belongs.

Posted by Charles Greenlee (Member # 3856) on 06-30-2006, 12:07 AM:

I thought this was in Afterlife? Maybe it was moved already, before I replied. Somehow it keeps showing up as having a new post, but that may be screwed up cookies.