Well guys it has been a while since i was here and its good to have something too share. I now have a full time 2pm-1am job and playtime has been cut short and finals are around the corner... However, I have been poking around my Pj and the Current set up is the Ushio with 36 MicroFrads overdrive on the pulse strike ballast. Now i am currious to know where the limit of our lcds is at with regard to washout. My PJ is pumping out a lot of light and my brightness controls on my liquid video are practicly useless... I noticed the problem when i watched dawn of the dead because when they are on the roof and write on the white dry erase boards i could not see what they were writting... TOO much White (light?) Now i believe my lcd has a contrast ratio of 350-400 :1 but i know there has to be threshold to the amount of light i can push through and still get good color. any one know what this is? I am planning on buying a new lcd in january because i have come to hate the slow response rate of this lcd....I want a 16ms Response time and better contrast if that is what i have maxed out. IS this the case? Is the contrast the one that is suffering because of the higher light output. It only got worse when i made my light pyramid/tunnel and dark blues became light blues and lightblues became white blues... What is the optimal lumen output we should be driving through our lcds? It seems the more light i pump in the less color i get out of it and that is just no good...I have also come find that the home depot phillips bulb gives a warmer color than the ushio and the venture (i have all three) why? Is it due to the mass or arc size? The phillips is much larger than the others...hmmm... I would like to find a happy medium so that other builders who have a specific goal will be able to achieve it with the proper specs on the lcd and lumen output. For example 300:1 = 1200 lumens optimal, 400:1 = 1600 lumens optimal, 500:1 = 1800 lumens optimal. I think this would help new builders and the rest of us as well.

Your thoughts guys?

Ezra

it must be the contrast ratio, i have had 2 of the 3 bulbs you have and have had no problems with it being too bright. I have noticed this, the brightness on some monitors does nothing when you adjust it, it adjusts the brightness of the backlight (which we do not have, thus it does nothing). You do not want the brightness and contrast set at 100 on some monitors, i noticed this with my old monitor, it made my light grays turn to white, and i lost my dark grays, they went to black, in other words, it was too much contrast. find a happy medium with the contrast and brightness, try and run a monitor calibration tool to find where you want it. if you arent running through a computer, try and find a movie with snow covered mountains, pause it and adjust, the intro to lord of the rings 2 should work, it has white whites, light and dark grays, and some blacks.

if you find that you cannot fix it, maybe get a ballast that offers a dimming feature.

avermedia tvbox-9 will solve your problems dude. The contrast on it will black your screen.

you think it may be a controller issue? i am running my all in wonder card on my pc and have tried tunning in the pic but again my ballast is overdriven so my light output is much higher than the normal 12 Microfarad driven ballast. Brainchild what do you think of this? Do you believe i can get rid of the problem with the tv-box9? Or is it that there is a threshold for light transmission through lcd panel?

Thanks Guys

Ezra

I think you might have answered your own question. Light that enters the fresnels from the wrong angle will stuff your contrast up. Fresnels don't reject light that is not coming from its focal point, they refract it the same as a normal lens does. My advice would be to remove the pyramid and see what happens.

DJ

I may be wrong, but I don't believe that non collumated light will affect the contrast of the projection. (It may cause unecessary heating of the panel.) Otherwise the diffuse light from a backlight would kill the contrast on a normal LCD. An LCD has two polarizing filters so that non collumated light will not pass through it.

Definately stray reflections after the panel would adversly affect the contrast of the projection, but not the light before it. Unless possibly brute lumen force can somehow overpower the polarizers.

I think that foamcows is right and you either have too many lumens for your panel's contrast ratio or your panel needs adjusting. If you can't get a good pic with adjustments, I would put in a safe capacitor and drive your bulb normally.(I would do that anyway) If you still have problems, then I would consider removing the light pyramid to get your lumens(/heat) down.

I think you may not be quite correct. If this was the case then lcd monitors would have very limited viewing angles and if light that is not perpendicular to the lcd was rejected, then tilting the lcd for keystone correction wouldn't work. I don't think polarisers are selective to incident light, they are selective to its polarity. If the collimated light is slightly off the ideal angle entering the fresnel, as would be the case when reflected off a light pyramid, then contrast will be affected and uncontrolled light would enter the front of the pj washing the image. Brute force will also play a small role. But I might be wrong.

DJ

I had very much this same problem with mine and i was using the HD bulb and it is warmer. But is also less lumens.i have a Liquid Video E15LCD1 400:1 25ms
the contast is in the middle of the adjustment
running rgb color temp on panel
and im using PowerDVD XP build 2417 there are full adjustments there for Brightness,contrast,saturation,color ect ect this helped a lot
then i found the adjustments on my video card its a Radeon ATI 7200
and on the tabs there is a Overlay adjustment this is the adjustment for anything not your desktop. and this fixed my color problems .I used starwars 5 at the beginning snow and caves ,snow was so white no detail at all,black no detail couldnt see darth vaders faces or lukes in the snow after the yeti attack.
now the snow has ripples like the ocean waves the sky is blue and gray with clouds,and darth looks like he does on my CRT.ive now switched to the HOR EYE from UL and the colors are even Brighter.
Heres my settings
Overlay on the video card
Brighness - 145
Contrast - 100
Saturation - 163
Hue - 0.0
Gamma - 5

Power DVD
Light - +32
Color1-2 - 0
color 3-4 - 0
Contrast - -5
Saturation - +32

Ihope this helps in some way to solve your Problems
Aiel Maiden

Actually, the fresnels do allow different degs. of light that do not come from the focal point to pass through.

to try this you can make a test stand with your collimator fresnel, field lens and a laser pointer. I set mine up with a laser level set to the focal length of the lens and this is what I found.

NOTE: this test is without an lcd panel and without getting the benifit of the polarizers on the lcd.

If the laser is at the focal point of the lens the light will go straight through. If the laser is tilted from the focal point to any part of the lens the light will go through and out the opposite angle it entered.

If the laser was pointed to any point of the lens while the laser was perpendicular to the lens but off of the focal point of the lens, approx 1/2 of the beam went through while 1/2 was rejected.

If I set the beam at an extream angle outside of the fresnel area 1/3 of the light was rejected 1/3 of the light fell between the lenses on the test stand 1/3 of the light made it through. the light that made it through however was a curved line on the test bench with different intensitys.

I then repeated the process with the laser at different lengths from the fresnel. From almost touching to 3' away. I got the same results, however the magnification of the beam changed.

Ok, so this all boils down to this. Light can go through the fresnels off axis from the focal point. However, it has little chance of ever reaching the projection lens because it is sent back off axis coming out of the field lens. Only a small amount of light that is sent through the lenses from a precise light tent with perfect angles and a lot of math, will ever reach the projection lens.

Ok, from what I tested and from my experiance with my projector, precision in alignment of the lenses will make or break the amount of contrast and usable light output. why? well if the lenses are off from one another the field lens will also reject some of the light. This causes the light it bounce back and hit the lcd again. This effect will brighten your picture overall but may also give uneven lighting. The picture from the lcd will look bright but hard to control with your lcd settings. blacks will gray out and colors will be lighter. Also you may see an increase in lcd temp., if the light gets slowed by this bouncing effect. while this may brighten the lcd, the light does not come out of the field lens at a usable angle to reach the projection lens. This effect causes loss of lumens that reach the screen.
I can tell you this because while adjusting my lenses all this happened. for light output I can go from barly able to see the picture with 1 room light on. to being able to see a picture in daylight with 3 room lights on. 1 of those lights being a ceiling light 3' infront of the screen. This all happened by adjusting the fresnels by no more than 1/8".

so inconclusion, to get the max light out of the projector with the most contrast and shades inbetween, look at your alignment and make the light transmision as fast as possable.

light that is not from the source is still transmitted by the fresnels, just think of the fresnel as a regular big lens, no matter if the light is coming from the focus, or from somewhere else, it will still pass thru the light and be diffracted, or rather, the speed of light changes, thus changing the angle, thus how lenses work.

anyways, the lens works best when the light is from the focal point, it does what we need it to do, which is change the direction of the light to one that flows evenly and perpendicular thru the lcd panel. if you have light that is not flowing parallel thru the panel it might be blocked.

the reason is the field of view of your monitor, this is caused by the polarizing filters, one for vertical, the other is horizontal, combined they allow only light that is coming on from a very distinct angle to pass thru the panel, the filters only allow this light to go thru. it is their job, it is how they work, it helps the monitor look crisp, the pixels look sharp, and it is how the monitor works, by controlling the light that passes thru either the red blue or green tinted pixels. without the filters the colors would be washed out and your monitor would look like a broken projector tv.

sorry for the bad grammar, i had a long day of work and im too lazy to correct it.