Real quick on the TUBING: Has anyone found 5" or wider fence tubing? 6" would be even better I think!
On GLASS: There are all sorts of different glass out there, if you talk to a framing company they have huge catalogs. I found a contact in the industry and will post some research results in the coming weeks.
To answer the question, though, I think HD glass DOES work, however, not "ideal". There is significant light reflection, which has to be blocked by your frame around the prisms. I even have reflection off the glass from the image from the MOVIE SCREEN itself, onto the front of the front prism, then back onto the screen! This is obviously taking away from the brightness of your picture but take into consideration that you are filling the screen with more pixels now, so, technically, you should be gaining on lumens, too.
Nice thing is, any little downfalls the basica model w/ cheap glass has, it's not bothersome enough to take them away, because of the PQ benefit you gain. Eventually I do want to make my final model w/ better quality glass. Anyone who finds a good source let us know. The only source I've found which sounds like it will work well (VERY anti-reflective) was a spin-off company which originated with edmund's scientific. I called the guy and told him the application, and he had a good solution, however, it was VERY pricy. Like $20 for a 5" x 5" piece. I didn't want to get into it at that time because I wasn't experienced yet at cutting glass, and, I was skeptical that regular glass might indeed work just fine. (which is does, almost).
On GLASS: There are all sorts of different glass out there, if you talk to a framing company they have huge catalogs. I found a contact in the industry and will post some research results in the coming weeks.
To answer the question, though, I think HD glass DOES work, however, not "ideal". There is significant light reflection, which has to be blocked by your frame around the prisms. I even have reflection off the glass from the image from the MOVIE SCREEN itself, onto the front of the front prism, then back onto the screen! This is obviously taking away from the brightness of your picture but take into consideration that you are filling the screen with more pixels now, so, technically, you should be gaining on lumens, too.
Nice thing is, any little downfalls the basica model w/ cheap glass has, it's not bothersome enough to take them away, because of the PQ benefit you gain. Eventually I do want to make my final model w/ better quality glass. Anyone who finds a good source let us know. The only source I've found which sounds like it will work well (VERY anti-reflective) was a spin-off company which originated with edmund's scientific. I called the guy and told him the application, and he had a good solution, however, it was VERY pricy. Like $20 for a 5" x 5" piece. I didn't want to get into it at that time because I wasn't experienced yet at cutting glass, and, I was skeptical that regular glass might indeed work just fine. (which is does, almost).
Update -
I was using a Hoya FL D filter and I removed it and it made all the difference. Also, the placement setup of the prisms was tricky. The picture is a little softer which makes me want to adjust the focus, but when text is on the screen, it is in focus.
The added panel usage has made the biggest improvement to 2.35 movies. They are soooo much brighter and improved.
BTW - I'm using a boxlight LCD projector which is very bright 1800 lumens.
The next version of the lens I will be using a very thin piece of clear acrylic and will be keeping it flush with the frame of the prism. I'm going to glue some segments of rubber band just below the edge of the prism and rest the acrylic on it so that it sits flush with the edge. This should give a much cleaner look and hopefully improve the focus by having less plexi glass to go through and keep the dimensions as close to the theoretical dimension. Hopefully I can put the filter back on since without it and using plexi-glass, the picture is very bright.
I still like the simplicity of an expansion lens. I'm currently not using a box to house the lens just resting them on their sides in front of the projector.
I was using a Hoya FL D filter and I removed it and it made all the difference. Also, the placement setup of the prisms was tricky. The picture is a little softer which makes me want to adjust the focus, but when text is on the screen, it is in focus.
The added panel usage has made the biggest improvement to 2.35 movies. They are soooo much brighter and improved.
BTW - I'm using a boxlight LCD projector which is very bright 1800 lumens.
The next version of the lens I will be using a very thin piece of clear acrylic and will be keeping it flush with the frame of the prism. I'm going to glue some segments of rubber band just below the edge of the prism and rest the acrylic on it so that it sits flush with the edge. This should give a much cleaner look and hopefully improve the focus by having less plexi glass to go through and keep the dimensions as close to the theoretical dimension. Hopefully I can put the filter back on since without it and using plexi-glass, the picture is very bright.
I still like the simplicity of an expansion lens. I'm currently not using a box to house the lens just resting them on their sides in front of the projector.
Cheap 5x5 tubinig
I dropped by a fencing contractor to see what kind of pvc posts they had. They gave me 4x4 and 5x5 pieces about a foot long from their cut-off pile.
Like JudeBarnes I'm making the lens for the 75U.
Question: should I make both prisms from the 4", both from the 5" or is there any advantage to making one from each size?
I dropped by a fencing contractor to see what kind of pvc posts they had. They gave me 4x4 and 5x5 pieces about a foot long from their cut-off pile.
Like JudeBarnes I'm making the lens for the 75U.
Question: should I make both prisms from the 4", both from the 5" or is there any advantage to making one from each size?
The rear prism doesn't need to be as large as the front, but you can make them both 5x5 or 4x4. I would recommend making the front 5x5 and the rear either 4x4 or 5x5. The plus side of making the rear prism smaller is that both prisms together take up less real-estate in front of yoru projector. One plus side to making them the same size is that it might be to your advantage in securing them more easily in place when making some kind of shell/housing around the prisms.
On my projector I don't think 4x4 will/would work for the front prism, it would probably cutoff the image once it was tilted at the appropriate angle, considering there is a small bit of air to contend with as well which eats into your total dimensions.
On my projector I don't think 4x4 will/would work for the front prism, it would probably cutoff the image once it was tilted at the appropriate angle, considering there is a small bit of air to contend with as well which eats into your total dimensions.
By the way very good idea on getting free fence tubing!! That's how I got my glass , too, went to a frame shop and asked for some scrap . The advantage to purchasing in the home improvement shop would be that they coudl cut it right there for you. (some of us don't have access to the necessary power tools!)
BUMP.
I will buy a NED HT1000 soon, maybe I'll make a new lens with better glass. In that case I'll try to engineer a method for changing prisms quickly and on-the-fly to compare turpentine with mineral oil.
Tor Arne
I will buy a NED HT1000 soon, maybe I'll make a new lens with better glass. In that case I'll try to engineer a method for changing prisms quickly and on-the-fly to compare turpentine with mineral oil.
Tor Arne
My webcam is looking through one of my anamorphic lenses now.
http://www.spotlife.com/users3/tahustvedt/webcam/
I could walk in front of it but I already look so bloody skinny without it. 🙂 Maybe I'll turn it on it's side so it makes me look fatter (look normal).
Tor Arne
http://www.spotlife.com/users3/tahustvedt/webcam/
I could walk in front of it but I already look so bloody skinny without it. 🙂 Maybe I'll turn it on it's side so it makes me look fatter (look normal).
Tor Arne
tahustvedt: What type of glass do you want to use? Did you know that there is a double prism version of the lens? Is has less chromatic abberation. It has four chambers with two different fluids.
That's the old lens. I will maybe order glass from Carl Zeiss, there's an optics dealer a Km from here.
The camera is a really bad Creative Webcam, hence the quality.
The double prism (quad) version is interesting, but I don't know the angles or which fluids to use.
Tor Arne
The camera is a really bad Creative Webcam, hence the quality.
The double prism (quad) version is interesting, but I don't know the angles or which fluids to use.
Tor Arne
There's an excel sheet in the german homecinema forum beisammen.de, but it is in german. You have to calculate the angles for each projector. The fluids used for this are Methylnaphtalin and Glycerin. Methylnaphtalin smells very bad.
I see. So the lens-shift and/or zoom of the projector is relevant to how the lens need to be.
I have the program, but I don't have Excel. 🙂
Tor Arne
I have the program, but I don't have Excel. 🙂
Tor Arne
2.35
I'm still very interested to come up with a lens system that will take a full panel 2.35 film and squeeze it back down to 2.35. I think DeCinema told me that the existing lenses could do it but there'd be a lot of barrel distortion.
The lens I made had it's oil prism start leaking from the plug, no big deal I'll just re-glue gun it. I'll doa better job on the new lens, which will be made from the fence tubing.
DeCinema/Thaustevedt: Do you seal your water/oil holes with just threading a (larger) screw into the (smaller) hole?
I'm still very interested to come up with a lens system that will take a full panel 2.35 film and squeeze it back down to 2.35. I think DeCinema told me that the existing lenses could do it but there'd be a lot of barrel distortion.
The lens I made had it's oil prism start leaking from the plug, no big deal I'll just re-glue gun it. I'll doa better job on the new lens, which will be made from the fence tubing.
DeCinema/Thaustevedt: Do you seal your water/oil holes with just threading a (larger) screw into the (smaller) hole?
I used silicone for the water prism. Don't use any other glue, it will leak. My first one leaked 2 or 3 months later. I also used silicon to close the prism when it was filled.
I used silicone to seal the hole. I just placed a dab of silicone to a piece of tape and taped it in place. When the silicone had hardened I removed the tape. It would probably be a better idea to create some sort of expansion-chamber though, by for example connecting a pipe or tube to the hole.
The barrel distortion will be more with a 2.35:1 lens. But it will not get any better by calculating special prisms for it. The barrel distortion is a result of the angle of the projector-lens, or throw ratio. A long-throw projector-lens will give less barrel distortion while a short-throw lens wil give more.
If you're gonna make a 2.35:1-lens you have to make the prisms bigger (taller) while retaining the correct angles because the prisms will need to be angled a lot more.
Can anyone post a picture of the mineral-oil bottle with the label visible, or type here what the label says so I know what kind of oil to ask for at the pharmacy? They have so many different mineral oils the "mineral oil" doesn't help.
Tor Arne
The barrel distortion will be more with a 2.35:1 lens. But it will not get any better by calculating special prisms for it. The barrel distortion is a result of the angle of the projector-lens, or throw ratio. A long-throw projector-lens will give less barrel distortion while a short-throw lens wil give more.
If you're gonna make a 2.35:1-lens you have to make the prisms bigger (taller) while retaining the correct angles because the prisms will need to be angled a lot more.
Can anyone post a picture of the mineral-oil bottle with the label visible, or type here what the label says so I know what kind of oil to ask for at the pharmacy? They have so many different mineral oils the "mineral oil" doesn't help.
Tor Arne
ok so I am working my way through this thread and the other websites around the web trying to figure out some onformation on this lens and I am wondering.
Is this lens good for large image short distance(lens to projected surface)? Basically I wanna make the largest image I can with the shortest distance possible.
Thanks for your time.
Is this lens good for large image short distance(lens to projected surface)? Basically I wanna make the largest image I can with the shortest distance possible.
Thanks for your time.
Someone recently posted in this thread they were using their lense (turned on it's side) to EXPAND the picture horizontally, you'd have to move your projector closer to the screen in that case, or, make a larger screen. As far as I know most people use the lens to COMPRESS the image vertically, as their projector may already be mounted, and no adjustments at all in throw are necessary.
MINERAL OIL
Tor/everyone: Here's a link to the actual product that I purchased to pour into the oilprism:
http://www.walgreens.com/store/product.jhtml?PRODID=606&CATID=100104
Tor: let me know if you need a better closeup of the product's label and I'll take one ASAP for you.
Tor/everyone: Here's a link to the actual product that I purchased to pour into the oilprism:
http://www.walgreens.com/store/product.jhtml?PRODID=606&CATID=100104
Tor: let me know if you need a better closeup of the product's label and I'll take one ASAP for you.
Ok, that link gives me something to look for. 🙂 If it's not too much trouble it would be really helpful with a bigger picture... 🙂
To make a horizontally expanding lens you need to lay it on it's side, but also turn it around so that you project the other way through it.
Tor Arne
To make a horizontally expanding lens you need to lay it on it's side, but also turn it around so that you project the other way through it.
Tor Arne