heya men, thought i start this up to look into curved screens and to see the disadvantages and the benifits a curved projection screen can give, ive been looking into this lightly for a while now, things i have found is projectors that are made for curved screens use cheaper lenses, the screen has a wider more evenly lit veiwing angle, and also interestingly the main reason they make curved screens is because the light of the center of the picture hits the screen at the exact same time as the outer of the screen, the screen also has a calculated angle to the lens wich is very presise. The only disadvantage i can see in a curved screen is the look of it, the size and room it takes up and personly i like things flat, but when it comes to image quality maybe that curved screen is that perfect choice. Any input on this matter would be apreciated and maybe we can make our own curved screens using cheap redily available lenses, ie double convex lenses wich are much brighter then a triplet as its only one lens, if we use a good quality double convex lens then u wont see ghosting and with the long focal that us fellows require with a ohp system the double convex isnt curved much at all meaning in return a curved screen that isnt too curved but curved enough for a perfect focus and a cheaper projection front end with excellent results.
Bring in the ideas
Trev
Bring in the ideas
Trev
Ace_3000
According to another post I read somewhere in this forum our DIY projectors which generally have a relatively short throw distance from the projector to the screen have a relativly large projection angle. This means that the light coming from the lens hits the furthest edges of the screen at a larger then desirable angle, and so the outer edges of the screen will be darker than the middle because lass of the light is reflected back to the viewer. A curved screen can help minimize this effect.
Hezz
According to another post I read somewhere in this forum our DIY projectors which generally have a relatively short throw distance from the projector to the screen have a relativly large projection angle. This means that the light coming from the lens hits the furthest edges of the screen at a larger then desirable angle, and so the outer edges of the screen will be darker than the middle because lass of the light is reflected back to the viewer. A curved screen can help minimize this effect.
Hezz
hezz
ya your right hezz on that note, and if the projection lens is small like the diylabs one the edges are also not as bright, another thing is if the lens is too close or close to the lcd it doesnt nesersearly cut the lcd off but it will be very dim on the edges because of the veiwing angle of the lcd's properties are out compared to the center veiwing angle where the lens is, not only that but the property of the lens isnt designed to handle those sorts of wider angles to project a perfect image, a good rule formula to follow is always try to find a lens that is no smaller than 1/10th scale of the lcd, that way it will be bright, the image will be projected more so without any deformalities and the projected image will have alot more of a uniform brightness over the entire area, when i got the diylabs triplet i was disapointed, it was smaller then what it says on his site, its not a 80mm triplet, its a 65mm triplet.
Trev
ya your right hezz on that note, and if the projection lens is small like the diylabs one the edges are also not as bright, another thing is if the lens is too close or close to the lcd it doesnt nesersearly cut the lcd off but it will be very dim on the edges because of the veiwing angle of the lcd's properties are out compared to the center veiwing angle where the lens is, not only that but the property of the lens isnt designed to handle those sorts of wider angles to project a perfect image, a good rule formula to follow is always try to find a lens that is no smaller than 1/10th scale of the lcd, that way it will be bright, the image will be projected more so without any deformalities and the projected image will have alot more of a uniform brightness over the entire area, when i got the diylabs triplet i was disapointed, it was smaller then what it says on his site, its not a 80mm triplet, its a 65mm triplet.
Trev
I would definetly build a curved screen If I had the time and space. Do you know if it has to be a specific curvature?
ehu
heya eh , basically its the same as the projection lenses curvature but it will also depend on the focal on the lens and the width of the beam, imax isnt hard to make, u use a fisheye lens, but finding the movies in that format is hard and trying to convert them has to be done frame by frame, making the projector is easy enough. The imax format is like a 4:3 ratio but its image is put side ways instead of up and down so the 4:3 is turned at 90deg and the image is run vertical, u can do that in the nview drivers actually.
Trev
heya eh , basically its the same as the projection lenses curvature but it will also depend on the focal on the lens and the width of the beam, imax isnt hard to make, u use a fisheye lens, but finding the movies in that format is hard and trying to convert them has to be done frame by frame, making the projector is easy enough. The imax format is like a 4:3 ratio but its image is put side ways instead of up and down so the 4:3 is turned at 90deg and the image is run vertical, u can do that in the nview drivers actually.
Trev
Ace, I'm glad someone said something about the DIY Lab lens. It's not 80mm! A few numbers he posts are off.
jcb
ya tell me about it, when i got it thought is was small, then i measured it, it was lol its not even 80mm to the outer ring edges its 79mm, as u know jcb majority of lenses if not all are measured as in clear lens diameter and thats the right way to measure them, but the diylabs isnt, its the measurment with the mounting ring and barrel included too! could be a selling point that somone started in the ohp's.
Trev
ya tell me about it, when i got it thought is was small, then i measured it, it was lol its not even 80mm to the outer ring edges its 79mm, as u know jcb majority of lenses if not all are measured as in clear lens diameter and thats the right way to measure them, but the diylabs isnt, its the measurment with the mounting ring and barrel included too! could be a selling point that somone started in the ohp's.
Trev
Guys,
I'm using the diylabs lens for experimentation but I would like to get a higher quality triplet of about 100mm and a focal length of 415mm later on. This would give me a better and more usable magnification ratio.
I'm building a hand made large lens from plastic to replace the second fresnel but i'm still in the process of making the wooden mold blank. I figure it will cost me about 130 USD to make two lenses. I'm interested in knowing how much degredation is caused by projecting the image through the fresnel.
Comparing a test of the DIYlabs fresnel and objective lens combination agains't using the used fujinon lens for the same image (only a portion of the image will show of course) but the fujinon lens is so superior at resolving the image that it is staggering. I 'm hoping that eliminating the second fresnel and replacing it with a large clear singlet lens and having a large quality objective will give better resolution than we are currently getting with the best DIY designs.
Hezz
I'm using the diylabs lens for experimentation but I would like to get a higher quality triplet of about 100mm and a focal length of 415mm later on. This would give me a better and more usable magnification ratio.
I'm building a hand made large lens from plastic to replace the second fresnel but i'm still in the process of making the wooden mold blank. I figure it will cost me about 130 USD to make two lenses. I'm interested in knowing how much degredation is caused by projecting the image through the fresnel.
Comparing a test of the DIYlabs fresnel and objective lens combination agains't using the used fujinon lens for the same image (only a portion of the image will show of course) but the fujinon lens is so superior at resolving the image that it is staggering. I 'm hoping that eliminating the second fresnel and replacing it with a large clear singlet lens and having a large quality objective will give better resolution than we are currently getting with the best DIY designs.
Hezz
Heres the specs on the AWI triplet I have :
f5/327 mm
Lens Diameter : 63.75mm
Barrow Diameter: 73.25mm
Flange Diameter: 87.90mm
Not much bigger then DIYLabs... but it is a brighter cleaner image. I hope to have pics soon. I'll have at least 5 on hand in a couple of weeks. So anyone interested should let me know. If they sell I'll have alot more on hand. They will sell for the same price as DIYlabs.
f5/327 mm
Lens Diameter : 63.75mm
Barrow Diameter: 73.25mm
Flange Diameter: 87.90mm
Not much bigger then DIYLabs... but it is a brighter cleaner image. I hope to have pics soon. I'll have at least 5 on hand in a couple of weeks. So anyone interested should let me know. If they sell I'll have alot more on hand. They will sell for the same price as DIYlabs.
This is what I got out of an article I read.
I belive this was on how movie theaters are setup or something to that extent. Basically since all the light from your projector is coming out from a point, the wider the screen is the longer it will take the light to reach the farther ends of the screen because the rays of light are traveling a diagonal path instead of a straight path [like the light hitting the center of your screen.] There was a great pic with a diagram of this basically showing that the light hitting the center was [for example] 40' feet distance, so the light traveling to the left and right edges of the screen was traveling 41' or 42' feet. When the screen is curved it will compensate for this. In their example it almost looked as though you could take a string to figure out the curve of your screen, because you just want the distance from your projection lens to be the same to all points on the screen.
It also talked about how some screens curve in at the top and bottom as the same is true, if your projector is dead center with your screen. It will take slightly longer to reach the top or bottom of the screen than it does to the center of it.
I will look around for the link and if I can find it I will post it here. It also had some cool ideas people would like about other things too. One part mentioned how perforated screens are used to position center, right and left channel speakers behind them to make the sound even more realistic. This way the sound you are hearing actually travels through the screen. For example if a character on the right side of the screen was talking, the sound would come from the right speaker so it would sound like it was coming directly from that person. I'm not sure if it would work exactly the same with DVD's but I have not really looked into my home theater sound setup yet. For now I am just trying to get my initial projector setup.
-Paul-
I belive this was on how movie theaters are setup or something to that extent. Basically since all the light from your projector is coming out from a point, the wider the screen is the longer it will take the light to reach the farther ends of the screen because the rays of light are traveling a diagonal path instead of a straight path [like the light hitting the center of your screen.] There was a great pic with a diagram of this basically showing that the light hitting the center was [for example] 40' feet distance, so the light traveling to the left and right edges of the screen was traveling 41' or 42' feet. When the screen is curved it will compensate for this. In their example it almost looked as though you could take a string to figure out the curve of your screen, because you just want the distance from your projection lens to be the same to all points on the screen.
It also talked about how some screens curve in at the top and bottom as the same is true, if your projector is dead center with your screen. It will take slightly longer to reach the top or bottom of the screen than it does to the center of it.
I will look around for the link and if I can find it I will post it here. It also had some cool ideas people would like about other things too. One part mentioned how perforated screens are used to position center, right and left channel speakers behind them to make the sound even more realistic. This way the sound you are hearing actually travels through the screen. For example if a character on the right side of the screen was talking, the sound would come from the right speaker so it would sound like it was coming directly from that person. I'm not sure if it would work exactly the same with DVD's but I have not really looked into my home theater sound setup yet. For now I am just trying to get my initial projector setup.
-Paul-
Here's the link...
I have a little time on my lunch break and have found the link I was referring to:
http://entertainment.howstuffworks.com/movie-screen.htm
This site is also really good for info on projectors and other related topics. I'm sure people have probably been here but for those that have not, this is a very interesting article with a bunch of good ideas.
-Paul-
I have a little time on my lunch break and have found the link I was referring to:
http://entertainment.howstuffworks.com/movie-screen.htm
This site is also really good for info on projectors and other related topics. I'm sure people have probably been here but for those that have not, this is a very interesting article with a bunch of good ideas.
-Paul-
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