I have acquired 2 opaque pjs both with 5in. diameter lenses. The Beseler vu-lite 2's lens is marked-18in. fl, the other, da-lite vu-lyte IV's lens is unmarked but seems similar and comes in a focusing mount.
I would like to build an inline pj but have several questions. I know that with a lot of digging thru the forums I could probably find most answers but I'm 69 (sure, play the age card) and I get distracted easily, so maybe someone could summerize? Please (my mother taught me to always say please).
#1 As I understand it, the layout from left to right would be:
Reflector, lamp, heat glass, fresnel, lcd pannel, fresnel, objective lens, screen. (the opaque pj came with a dimpled trapazoidal reflector- any use?)
#2 Will a 400W MH provide enough light for a great picture in a room with enough light to read in if you wanted to ruin your eyes, at a screen to lens distance of 7 to 20 ft.? How bright are xenon auto head lights?
#3 What is the advantage of 17in. lcd's over 15 in. ones.?
Higher resultion, better contrast, better conections? Does it require more light and is it worth it dollar-wise?
#4 I see the wisdon of ajustable componets for tweeking purposes but can someone give me some starting distances to use with the 18in. lens and the best choice in fresnal lens fl's (all this for the winner of the 15in.-17in. question.
Anything else anyone wants to tell me would be appreciated.
BTW Does anyone know how much these 18in. lenses are worth, I think I can get a couple more.
I would like to build an inline pj but have several questions. I know that with a lot of digging thru the forums I could probably find most answers but I'm 69 (sure, play the age card) and I get distracted easily, so maybe someone could summerize? Please (my mother taught me to always say please).
#1 As I understand it, the layout from left to right would be:
Reflector, lamp, heat glass, fresnel, lcd pannel, fresnel, objective lens, screen. (the opaque pj came with a dimpled trapazoidal reflector- any use?)
#2 Will a 400W MH provide enough light for a great picture in a room with enough light to read in if you wanted to ruin your eyes, at a screen to lens distance of 7 to 20 ft.? How bright are xenon auto head lights?
#3 What is the advantage of 17in. lcd's over 15 in. ones.?
Higher resultion, better contrast, better conections? Does it require more light and is it worth it dollar-wise?
#4 I see the wisdon of ajustable componets for tweeking purposes but can someone give me some starting distances to use with the 18in. lens and the best choice in fresnal lens fl's (all this for the winner of the 15in.-17in. question.
Anything else anyone wants to tell me would be appreciated.
BTW Does anyone know how much these 18in. lenses are worth, I think I can get a couple more.
lots of questions!
1) That's a usable layout known as a split-fresnel straight-shooter design. There are other possibilities, like adding a mirror or two to fold the light or image path to make a smaller box. Or putting both fresnel before the LCD. (No, your reflector is not usable for a projector.)
2) 400 Watts of MH will give you a great picture, if it is around 100" diagonal. If you turn on lights in the room, it will wash out your blacks so you get a lower contrast image. Add enough ambient light and you can wash it out completely. (Xenon auto headlights are not bright enough.)
3) 17" LCDs have higher resolution than 15", better contrast ratios, quicker response time, and many have a digital interface. But 15" LCDs are still good enough to make very fine projectors, and it is a lot easier to get a projection lens to work with a 15". 14" LCDs are not quick enough, and don't have very good contrast ratios. 15" or 15.4" is the "sweet spot" right now.
4) For a 15" LCD, 18" fl lens, 100" image:
Get a 220 mm fl fresnel and a 550 mm fl fresnel from 3dlens.com.
lamp arc to 220 fresnel: 220 mm
220 fresnel to LCD: 10 mm (fresnel rough side faces LCD)
LCD to 550 fresnel: 10 mm (fresnel rough side faces LCD)
LCD to center of projection lens: 20.7"
center of projection lens to screen: 138"
You should also get a piece of DIYprojectionCompany.com's IR filter glass to put between the lamp and the first fresnel. Also get a piece of Lexan XL from Home Depot to support your 220 fresnel. Lexan is a great UV filter. Don't forget a fan or two to remove hot air from around the lamp.
My 18" OHP lens cost me about $65, but I have seen them go for as little as $12 on eBay. Most are $60-75. But this is essentially the same lens as some DIY stores have been selling for $110-120.
1) That's a usable layout known as a split-fresnel straight-shooter design. There are other possibilities, like adding a mirror or two to fold the light or image path to make a smaller box. Or putting both fresnel before the LCD. (No, your reflector is not usable for a projector.)
2) 400 Watts of MH will give you a great picture, if it is around 100" diagonal. If you turn on lights in the room, it will wash out your blacks so you get a lower contrast image. Add enough ambient light and you can wash it out completely. (Xenon auto headlights are not bright enough.)
3) 17" LCDs have higher resolution than 15", better contrast ratios, quicker response time, and many have a digital interface. But 15" LCDs are still good enough to make very fine projectors, and it is a lot easier to get a projection lens to work with a 15". 14" LCDs are not quick enough, and don't have very good contrast ratios. 15" or 15.4" is the "sweet spot" right now.
4) For a 15" LCD, 18" fl lens, 100" image:
Get a 220 mm fl fresnel and a 550 mm fl fresnel from 3dlens.com.
lamp arc to 220 fresnel: 220 mm
220 fresnel to LCD: 10 mm (fresnel rough side faces LCD)
LCD to 550 fresnel: 10 mm (fresnel rough side faces LCD)
LCD to center of projection lens: 20.7"
center of projection lens to screen: 138"
You should also get a piece of DIYprojectionCompany.com's IR filter glass to put between the lamp and the first fresnel. Also get a piece of Lexan XL from Home Depot to support your 220 fresnel. Lexan is a great UV filter. Don't forget a fan or two to remove hot air from around the lamp.
My 18" OHP lens cost me about $65, but I have seen them go for as little as $12 on eBay. Most are $60-75. But this is essentially the same lens as some DIY stores have been selling for $110-120.
Thanks, Guy
Your explanation answered everything I asked and more. It makes things easy.
I'm not concerned with the size of the box so don't need mirrors, but is a split fresnel system better-same-worse than having both lenses on the light side of the lcd?
I see that there are 17in. monitors with 1280x1024, 500:1, 12ms responce for under $200 and if my lens will cover the corners, I think I will go that way. Would this change the set up distances
I saw the posts in the lighting forum and ordered the hps ballist on e-bay. What would be the best reflector to use with the Ushio UHI-S400DD bulb with a 17in pannel?
this is getting more fun everyday
Your explanation answered everything I asked and more. It makes things easy.
I'm not concerned with the size of the box so don't need mirrors, but is a split fresnel system better-same-worse than having both lenses on the light side of the lcd?
I see that there are 17in. monitors with 1280x1024, 500:1, 12ms responce for under $200 and if my lens will cover the corners, I think I will go that way. Would this change the set up distances
I saw the posts in the lighting forum and ordered the hps ballist on e-bay. What would be the best reflector to use with the Ushio UHI-S400DD bulb with a 17in pannel?
this is getting more fun everyday
dvb said:
I would also like to know. assuming that both fresnels on the same side design is worse....how much worse? I'm not going for a HD picture...just something to watch movies on every now and then.
split vrs unsplit
Actually, unsplit designs (both fresnels together before the LCD) give you a sharper screen image, because fresnels are not very good at focussing images.
There are three reasons to use a split design:
1) You can tilt the field fresnel (the one after the LCD) to get some optical keystone correction, in case you can't put your projector perpendicular to the center of the screen.
2) Your LCD may not have sufficient viewing angle to match the angle of rays at the corners of a non-split design. Then you would see viewing angle artifacts at the edges of the screen. Excessive angle can also make the image dimmer around the edges, because of the light path through the LCD cells. In a split design, the rays are mostly perpendicular to the LCD surface, so these problems are absent.
3) Your lens focal length and throw distance define the LCD to lens distance, and your fresnels have to focus the lamp arc image into the projection lens. It may be easier to make that happen with the field fresnel 30-40 mm closer to the projection lens.
I always recommend that builders try both, to see which looks better with their particular set of parts & distances.
Actually, unsplit designs (both fresnels together before the LCD) give you a sharper screen image, because fresnels are not very good at focussing images.
There are three reasons to use a split design:
1) You can tilt the field fresnel (the one after the LCD) to get some optical keystone correction, in case you can't put your projector perpendicular to the center of the screen.
2) Your LCD may not have sufficient viewing angle to match the angle of rays at the corners of a non-split design. Then you would see viewing angle artifacts at the edges of the screen. Excessive angle can also make the image dimmer around the edges, because of the light path through the LCD cells. In a split design, the rays are mostly perpendicular to the LCD surface, so these problems are absent.
3) Your lens focal length and throw distance define the LCD to lens distance, and your fresnels have to focus the lamp arc image into the projection lens. It may be easier to make that happen with the field fresnel 30-40 mm closer to the projection lens.
I always recommend that builders try both, to see which looks better with their particular set of parts & distances.
Question about Viewing Angle and Contrast Ratio
Hi, I found a cheap 17" LCD Monitor at CompUSA (Link below), but I am concerned about the low vertical (125) and horizontal (140) Viewing Angle, as well as the 450:1 contrast ratio.
If I spend more money to get an LCD with 160 degrees (Ver. & Hor.) viewing angle and 600:1 contrast ratio would that make a large visible difference?
Link to the monitor's product spec. page:
http://www.compusa.com/products/product_info.asp?product_code=318020&pfp=cat3
Thanks for any help you can give,
Tyler Heatherly
Hi, I found a cheap 17" LCD Monitor at CompUSA (Link below), but I am concerned about the low vertical (125) and horizontal (140) Viewing Angle, as well as the 450:1 contrast ratio.
If I spend more money to get an LCD with 160 degrees (Ver. & Hor.) viewing angle and 600:1 contrast ratio would that make a large visible difference?
Link to the monitor's product spec. page:
http://www.compusa.com/products/product_info.asp?product_code=318020&pfp=cat3
Thanks for any help you can give,
Tyler Heatherly
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