Hi All,

If you had an option to use a 6500K bulb costing around $200 (including ballast), or a 5500K light source costing around $100 (including converter) would there really be a significant difference in your projector performance?

thats not enough info to make a decision. post up the exact bulbs and ballasts you're considering and we can give an opinion

Hehe, Ok you got it! The Lumen Labs MH 6500k Bulb and Ballast verus an White LED Array putting out 5500K , is this enough information?

well these are two completely different light sources, but hey 5500K is just fine

What LED array are you considering? Im curious about this also. And will it put out enough light like the 6.5k.

LED arrays have a couple pitfalls.. they generate a lot of heat, they are relatively expensive (I'd like to see what you plan ot use for $100), and don't put out too much light. They should however, allow you to run without a collimating fresnel since they put out a decent amount of parallel light, unlike a single arc. Another downside is the need to use a small panel, unless you want to construct a giant array. There's a couple plogs of people experimenting with these.

$175 would be closer to the real price if you consider the fact that we use:

1. Bulb
2. Ballast
3. Precondensor
4. Collimating Fresnel
5. Reflector

But it would depend on how well the LED array performs in contrast and brightness on the screen. Temperature does not matter. We can make a bulb 3000k make white light.

I was looking at this LED Array, and thought it was comparable to the MH bulb.

http://www.laminaceramics.com/docs/BL_3_White_55.pdf

It sells for only $85 bucks, and I am thinking I could use 1 and just replace the 1. Bulb and 2. Ballast with it.

Your toughts?

If I'm readign the spec sheet right... it measures 17x30mm. How many of those would you need to cover a 15" monitor @ $85 each?

My thoughts were only 1 if you were still using the reflector and Fresnel Lens , anyone else?

huh.. these are only going to project light forward.. a reflector in the back won't do anything. you do not want to use a fresnel with a small LED array because it wouldn't do anything. you basically need an array as large as the screen, or a single very bright LED.

Please see my post in another section at : http://www.lumenlab.com/forums/index.php?s...mp;#entry184239

But to save you time, here is the same thing:

Couldn't you use a wide beam flood dispersion such as this ? http://www.laminaceramics.com/docs/BL_3000_Optics.pdf

Wouldn't it take the small LED source and give enough light for the LCD?

No I don't think that would work very well w/o a fresnel, and even then it would have poor light distribution. The goal is to get collimated (parallel) light to the field fresnel so it can be directed to the triplet. The collimating fresnel will only converge light to the triplet which hits it near perpendicularly. There are two main ways to do this: 1) have a light source which produces already parallel light, such as an LED array as large as the panel, or a large parabolic rerflector. 2) have a near point source at the focal point of a collimating fresnel. the fresnel cannot collimate light with the incorrect indicent angle.

hrm actually after thinking about it for a minute, I think it could work, but you would need a collimating fresnel for sure, and the distribution would not be great.. the center would probably be 2x as bright at the area outside the LED array. see diagram. LED array could probably produce light which would hit everywhere on the fresnel at the same incident angle as light would when originating from its focal point, but it would also produce a good amount of already parallel light in the center which would create a hotspot. without a fresnel, the area outside the LED array would be extremely dim. I wonder if any of the people using LED arrays have also used a fresnel? of course I am assuming paralle llight hitting the outside of the fresnel will not be diverted.. is this incorrect?