| Khmann002 |
| Can anyone help me find a projection lens with a focal lenght of 155mm or something close. The lcd is 5inch diag. thats being projected. |
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| ace3000_1 |
| quote: | | Can anyone help me find a projection lens with a focal lenght of 155mm or something close. The lcd is 5inch diag. thats being projected. |
Unless your top frensel has a focal thats near 155mm then it aint going to work so good.
Trev |
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| Khmann002 |
| You say top fresnel ace, are you talking about a fresnel in front of the lcd? If you are I dont have a fresnel in front of my lcd. |
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| jcbklyny |
Even if the fresnel is behind the LCD, you'll get the brightest possible picture getting a fresnel with a little longer focal length then your projection lens. Account for the inch or so between the fresnel and LCD and your ideal focal length fresnel would be about 180-185mm. A standard 220 or 330mm fresnel used for the 15" projects is too big.
You would have to move the fresnels up away from the light source to shrink the top focal length. This is not recommended.
- JCB
www.diybuildergroup.com |
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| spectreag |
| I bought the same lens that Ace has for my projector. It is a great lens for small lcd's in enclosures. After some more investigating, I found dozens of copy machine sales and service businesses in my town and contacted them. Almost all of them had older machines that were not being used or out of service, and most of them said that I could have any lens I wanted for free or very very cheap( less than $10 us). Most of the lenses in these copiers are of high quality, especially if you find one in a high volume output copier. I was able to obtain a five element lens with a heavy ar coating for free. I tested it on my test-bed projector ( slide projector w/ 3" lcd and 300w halogen), and the result was amazing. It was much more clear and crisp with much less keystone effect than either the surplus shed lens or the diy labs triplet. Just make sure that the focal lenght of the lens is longer than your lcd panel is wide. Unfortunately, the lenses out of new copiers will not work because they have changed to very small lenses that focus the image onto a ccd, so if you are looking at newer copiers forget it. I hope this may help anyone with a projection lens dillema. Anyone have questions just let me know! |
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| bobharry |
| If you use two 330mm focal top fresnels that will cut the focal in half, which would be good for using a lens with the focal of the lenses brainchild linked to. |
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