Just to let people know, I built the two glass plate prism with glycerin design that slize proposed and did some initial tests over the weekend.
Seems to work OK, although I did notice some softening of the picture and a slight barrel distortion. I'll run some more tests in the comming days.
I have a BENQ6100 mounted right on axis with with screen due to my room limitations and using the prisms was able to reduce the keystone correction somewhat.
So far so good.
Best Regards,
Skippy31
Seems to work OK, although I did notice some softening of the picture and a slight barrel distortion. I'll run some more tests in the comming days.
I have a BENQ6100 mounted right on axis with with screen due to my room limitations and using the prisms was able to reduce the keystone correction somewhat.
So far so good.
Best Regards,
Skippy31
Just an update on my lense. Was able to eliminate most of the distortion that I mentioned by adjusting the lense in respect to the projector. There is still a very slight softening of the picture but most of that was corrected when I gave the prisms a final cleaning. Overall very happy with this project.
Best Regards,
Skippy31
Best Regards,
Skippy31
hey skippy what do you mean buy "adjusting the lenses in respect to the projector" did you slightly adjust the angles or separate the prisms or something? I also have a benq 6100 and have built my anamorphic lens. It works great but I also have a slight softening of the image and barrel distortion. I can live with it though but just interested in what you did to help alleviate the problems.
To every one else my biggest problem is I have a bad glare problem. If I look at white text on a black background I see a dim copy of the text in the background. I am looking at getting some Denglas, TruVue UltraClear, or the Sandel CrystalView glass. All three have an optical coating like camera lenses that help get rid of the glare. Supposedly people do not even notice that the picture has glass on it with these glass types. I have not got prices but I think it will be cheaper than museum glass. I also bought some of that Vision Clear anti-glare spray for tvs that is supposed to get rid of glare. I am going to try it out and let every one here know if it is any good. I am worried that it will blur the image like the normal acid etched anti reflective glass but I will find out and let every one know. I am very pumped about this thread because I almost bought the retail anamorphic powerbuy lens but now am very glad that I did not because with just a few dollars and time I have gotten very promising results. (sorry if Denglas, TruVue UltraClear, Sandel CrystalView, or Vision Clear have been discussed before but did not see any threads about them so I thought I would share.)
To every one else my biggest problem is I have a bad glare problem. If I look at white text on a black background I see a dim copy of the text in the background. I am looking at getting some Denglas, TruVue UltraClear, or the Sandel CrystalView glass. All three have an optical coating like camera lenses that help get rid of the glare. Supposedly people do not even notice that the picture has glass on it with these glass types. I have not got prices but I think it will be cheaper than museum glass. I also bought some of that Vision Clear anti-glare spray for tvs that is supposed to get rid of glare. I am going to try it out and let every one here know if it is any good. I am worried that it will blur the image like the normal acid etched anti reflective glass but I will find out and let every one know. I am very pumped about this thread because I almost bought the retail anamorphic powerbuy lens but now am very glad that I did not because with just a few dollars and time I have gotten very promising results. (sorry if Denglas, TruVue UltraClear, Sandel CrystalView, or Vision Clear have been discussed before but did not see any threads about them so I thought I would share.)
Hey Ninja,
I found that most of my geometric distortion was caused by adjustments of the lense with respect to the projector. As in twisting the lense left to right. Perhaps barrel distortion was not 100% the right term, but between adjusting keystone on the projector and twisting the lense with respect to the projector I was able to restore the image to be properly rectangular.
The prism angles (with respect to each other) of course determine exactly what aspect ratio you end up with in the end.
Softening well that's another issue....
BTW I'm not having too many issues with reflections, but my projector is mounted behind my wall and any reflections end up on the furnace room ceiling...
Best Regards,
Skippy31
I found that most of my geometric distortion was caused by adjustments of the lense with respect to the projector. As in twisting the lense left to right. Perhaps barrel distortion was not 100% the right term, but between adjusting keystone on the projector and twisting the lense with respect to the projector I was able to restore the image to be properly rectangular.
The prism angles (with respect to each other) of course determine exactly what aspect ratio you end up with in the end.
Softening well that's another issue....
BTW I'm not having too many issues with reflections, but my projector is mounted behind my wall and any reflections end up on the furnace room ceiling...
Best Regards,
Skippy31
Mirror use a "bust" ?
Has the ideas of using a mirror(s) been proven ineffective to compress or expand an image? I don't see why you'd need two mirrors, seems like you can invert the picture using HTPC software, point the projector the opposite direction and using a single, curved mirror surface in front of it, to push the compressed image back at the screen.
As I understand it, someone said that certain areas of the image would be distorted?
Has the ideas of using a mirror(s) been proven ineffective to compress or expand an image? I don't see why you'd need two mirrors, seems like you can invert the picture using HTPC software, point the projector the opposite direction and using a single, curved mirror surface in front of it, to push the compressed image back at the screen.
As I understand it, someone said that certain areas of the image would be distorted?
A single mirror doesn't work, except with a pinhole lens i.e. one that only fucuses one ray of light on each point of the screen. Unfortunately, a pinhole lens would make for a very dark projected picture. In the area of illumination of the screen, a projection lens is the opposite of a pinhole lens. It needs to be big to let enough light through to the screen.
In a normal direct projection setup, every point on the screen receives a ray of light from every point on the surface of the projection lens in order to make the picture bright. Focusing the lens ensures this happens.
With a curved mirror interposed between the projection lens and the screen, rays of light from the surface of the lens hit the mirror (on their way to the screen) at different points of its curve. Hence they will be deflected at different angles and, instead of all converging on the desired single point on the far screen, will arrive at a cluster of different points and the image will be blurred.
A curved screen would fix (or at least ameliorate) the problem but would add a whole new level of complication to the anamorphic mechanism.
Throwing the projection lens out of focus to try and "bias" the image before reflecting it off the curved mirror would not work, even in theory, because you're trying to make a flat-field image "fit" a curved mirror and after that a flat screen. The only way of "biasing" the projector image is with an anamorphic lens, which brings us back to the problem we started with.
Catch-22.
In a normal direct projection setup, every point on the screen receives a ray of light from every point on the surface of the projection lens in order to make the picture bright. Focusing the lens ensures this happens.
With a curved mirror interposed between the projection lens and the screen, rays of light from the surface of the lens hit the mirror (on their way to the screen) at different points of its curve. Hence they will be deflected at different angles and, instead of all converging on the desired single point on the far screen, will arrive at a cluster of different points and the image will be blurred.
A curved screen would fix (or at least ameliorate) the problem but would add a whole new level of complication to the anamorphic mechanism.
Throwing the projection lens out of focus to try and "bias" the image before reflecting it off the curved mirror would not work, even in theory, because you're trying to make a flat-field image "fit" a curved mirror and after that a flat screen. The only way of "biasing" the projector image is with an anamorphic lens, which brings us back to the problem we started with.
Catch-22.
I used to own a 1980-ish front projection television that came out of some bar somewhere, it actually shot the light towards the audience, but a hinged, fold-out cover (which housed the RGB guns) had a mirror on the back side would reflect the light back up at the screen. The screen was CURVED. (Curved in at the corners). This mirror was completely flat but somehow the angle of the mirror must also cause for a need for the curved corners. (perhaps to correct for keystone or other effects of reflecting at that angle?)
Well I finished my second set of anamorphic lenses and I am pretty happy. I ended up getting some truevue ar glass. I was able to get enough truvue glass to make two sets of anamorphic lens for cheaper than it would have cost to make one set of museum glass prisms. It was very hard to find any special glass in my city I actually had to take a two hour tip to get this glass. The only problem it has a slight greenish tint to it but it does not really affect image quality. The good news it did remove my ghosting problem that I had with normal glass. The only problems I have now is I have barrel distortion but for some reason only at the top of the image the bottom seems to be fine. Very strange, has any one else noticed this? And, I also have some chromatic abrasion problems. I am using the distilled water mineral oil combination, would it help to use the distilled water turpentine oil combination? It is not very bad but I do notice it some times especially white on black screens.
I also tried out that Vision Clear anti-glare spray and it worked just like I thought it would. It leaves a slight matt finish to the glass and just makes the image blurry when you project with it. I was able to get a similar effect with a very fine mist of hair spray on the glass. I think the hair spray actually worked better because it was clearer than the vision clear stuff. Either way the vision clear or the hair spray is not good for projection.
I guess I am going to make another set to try to fix the barrel problem and if any one can let me know if turpentine works better than mineral oil I might try that also. Also does any know since my barrel distortion is only at the top if I should just bend the top and not the bottom?
I also tried out that Vision Clear anti-glare spray and it worked just like I thought it would. It leaves a slight matt finish to the glass and just makes the image blurry when you project with it. I was able to get a similar effect with a very fine mist of hair spray on the glass. I think the hair spray actually worked better because it was clearer than the vision clear stuff. Either way the vision clear or the hair spray is not good for projection.
I guess I am going to make another set to try to fix the barrel problem and if any one can let me know if turpentine works better than mineral oil I might try that also. Also does any know since my barrel distortion is only at the top if I should just bend the top and not the bottom?
Marco T said:
Marco
Just wondering if this worked out.
Has anyone else used cylindrical lenses successfully?
dual lense?
Rather than building a very LARGE lense to try and accomplish 2.35 compression on a 4:3 projector... is it possible to build two small ones to compress 1.85 down to 2.35?
What happens to the image if you pass it through 4 total water/oil prisms?
Rather than building a very LARGE lense to try and accomplish 2.35 compression on a 4:3 projector... is it possible to build two small ones to compress 1.85 down to 2.35?
What happens to the image if you pass it through 4 total water/oil prisms?
Just a guess but I would think lots of detail distortion as opposed to squeze unsqueeze distortion.
Jude,
Have you tried rotating both of the lenses slightly to change the compression or expansion and see if you get an adequate picture. I don't know how to explain this without a picture but if you look at the original patents for the lenses they had adjustable compression or expansion depending on how the lens was oriented.
Hezz
Have you tried rotating both of the lenses slightly to change the compression or expansion and see if you get an adequate picture. I don't know how to explain this without a picture but if you look at the original patents for the lenses they had adjustable compression or expansion depending on how the lens was oriented.
Hezz
Re: dual lense?
You would most likely see reduced contrast and light output. I think that the best bet is to try to find some surplus optical quality prisms.
I recently ordered two 73mm coated wedge prisms (these were made from optical glass and actually looked like round lenses) which were on sale at surplusshed.com for $5 a piece to experiment. The result: the squeeze can be done, BUT, each prism bent the light so little that getting an anamorphic squeeze/expansion required angling the 2 prisms so much that the projected image was a little bigger than the 2nd prism. I have an Optoma H30, which is a relatively short throw projector, so whichever method you use, I'd recommend either a) using an anamorphic lens only with a long throw projector, or b) using REALLY big prisms.
While I was working with the prisms I also noticed that the contrast was impacted and on an 800x600 resolution projector the screen door effect wasn't reduced enough to warrant putting any more work into the project, at least for now.
JudeBarnes said:
You would most likely see reduced contrast and light output. I think that the best bet is to try to find some surplus optical quality prisms.
I recently ordered two 73mm coated wedge prisms (these were made from optical glass and actually looked like round lenses) which were on sale at surplusshed.com for $5 a piece to experiment. The result: the squeeze can be done, BUT, each prism bent the light so little that getting an anamorphic squeeze/expansion required angling the 2 prisms so much that the projected image was a little bigger than the 2nd prism. I have an Optoma H30, which is a relatively short throw projector, so whichever method you use, I'd recommend either a) using an anamorphic lens only with a long throw projector, or b) using REALLY big prisms.
While I was working with the prisms I also noticed that the contrast was impacted and on an 800x600 resolution projector the screen door effect wasn't reduced enough to warrant putting any more work into the project, at least for now.
Guys,
Is this company called Prismasonic new as I haven't seen thier adjustable anamorphic lenses before. They make a vertical squeeze model and a horizontal stretch model. Lenses are either singlet glass or achromatic (doublet) glass prisms for higher imaging quality.
Knobs turn to get exact adjustment.
Hezz
Is this company called Prismasonic new as I haven't seen thier adjustable anamorphic lenses before. They make a vertical squeeze model and a horizontal stretch model. Lenses are either singlet glass or achromatic (doublet) glass prisms for higher imaging quality.
Knobs turn to get exact adjustment.
Hezz
Attachments
Is it worth the effort?
Newbie to this thread. But NOT a newbie to lenses or Home Theater.
Okay. I've read all 38 pages of this forum, and have taken my notes, made my schematic drawing, and tonight I"m going to go out and buy the materials.
What I'm wondering, is... Is it worth it?
I've spoken to a couple people who have done this, and less-than a year later, they've all dismantled their lenses to use their projector sans-lens. They say it looks better.
Anyone out there think differently?
Also, does the concencus show that if you want to stretch your picture horizontally, all that is required is a flip of the finished lens (a 90 degree rotation?)
This thread has died down quite a bit, so I don't expect an answer soon, but, hey-- I can hope!
Newbie to this thread. But NOT a newbie to lenses or Home Theater.
Okay. I've read all 38 pages of this forum, and have taken my notes, made my schematic drawing, and tonight I"m going to go out and buy the materials.
What I'm wondering, is... Is it worth it?
I've spoken to a couple people who have done this, and less-than a year later, they've all dismantled their lenses to use their projector sans-lens. They say it looks better.
Anyone out there think differently?
Also, does the concencus show that if you want to stretch your picture horizontally, all that is required is a flip of the finished lens (a 90 degree rotation?)
This thread has died down quite a bit, so I don't expect an answer soon, but, hey-- I can hope!
Hi
I also started making my anamorphic lens (vertically compressing)with glyserine filled prisms.My first attempt was with very cheap quality glass,the result was fuzzy picture and some barrel distortion.But I still wanted to test how it will turn out with good quality qlass and all the sides aligned correctly.
Will probably finish the lens this weekend and reply here if the results are satisfactory.
I also started making my anamorphic lens (vertically compressing)with glyserine filled prisms.My first attempt was with very cheap quality glass,the result was fuzzy picture and some barrel distortion.But I still wanted to test how it will turn out with good quality qlass and all the sides aligned correctly.
Will probably finish the lens this weekend and reply here if the results are satisfactory.
I made one with two plastic lenses sourced from an optometrist. Worked beautifully. Weighed 4 ounces.
Alcheringa said:
Can you go into specifcs with this? Plastic prism's as described in this thread, or something else?
Also, what's the concensus on "cheap" glass? I wasn going to use "Tru Vue" glass from Michael's (hobby store) anyone try using that??
The cheap glass I used for testing was cutted from an old picture frame glass.
I suppose any high transparency glass with anti reflex coating will do.The glass I'm useing is from Edmund optics and 8"x10" piece did cost about 70Euros with postage.
I suppose any high transparency glass with anti reflex coating will do.The glass I'm useing is from Edmund optics and 8"x10" piece did cost about 70Euros with postage.
I didn't use prisms at all, they're too bulky. Apart from my new plastic lens, I also have an original Panavision "Anamorphotic" adapter, circa 1951 vintage, a prism system, but its sheer bulkiness interfered with the IR signals from the remote control. Lotsa problems. Heavy too, at 12 pounds. Beautiful pictures, though, as each prism is achromatic.
The optometrist option involved me working out how cylindrical anamorphic lenses work, picking the appropriate diopter lenses that could be made by optometrist supply comanies, and then paying $100 for a set of them. Three days later they arrived, I put them into a cardboard tube, and (after some initial fiddling) they have been working pretty well ever since. There is some chroma fringing but I'm not sure if this is due to my mounting "technique (i.e. the optical axes may not be exactly aligned, and there may be some tilt as well), but the results are very acceptable. A big "wow" factor for the uninitiated who come to my house for a movie. The lenses were not stock focal lengths, so they had to be specially ground for my application. There is an extra charge for this.
There was no refocusing of the projector required either. It's a truly "afocal" system.
I'm not sure if my lens is off-topic or not, as this seems to be a thread about prismatic adapters that are made from scraps of glass, not adapters (like mine) that are ground to a high level of precision i.e. not "DIY", strictly speaking.
Someone upthread mentioned a curved mirror system and asked whether that would work. It will, but you need need mirrors each with a different curve and a method of getting them out of each other's way (not easy, actually). Spacing is of fundamental importance with cylindrical systems (mirrors, refractive lenses) and it is this spacing that usually causes the main mechanical problems. I haven't made a mirror version, but I've modelled it and it would work if I could find someone who could machine the curves accurately enough for me (and they have to be VERY accurate). Once again, not really a DIY process as in "Do It Yourself", more a "Design It Yourself" and then get someone competent (with the right NC tools) to make it for you.
Interestingly, I also designed a glass cylindrical lens with three elements, front, rear and one in the middle for focus correction. These lenses are ground accurate to 0.1 of a millimetre radius in China and are heavier than the plastic optometrist version, but have much less chromatic aberration. They are anti-reflection coated and produce an image 120 inches wide at 15.5 feet that is actually 30% brighter than the "traditional" widescreen method, which is to simply enlarge the picture until it fills the width of the screen (letting the letterbox bands spill off the top and bottom).
With my lenses I use the expansion technique, widening the picture by 1.33. This means I can reduce the height and get a brighter "base" picture to start with. The AR coatings mean I only lose a further 1.8% through the lens on top of the 25% I lose from expansion, of course.
Both vertical compression and horizontal expansion end up with the same final picture brightness. I prefer expansion because it's more convenient when I remove the lens not to have to re-zoom the projector for a smaller screen height.
A note on cost: my custom-ground glass lens sourced from China actually cost a fraction of what Panamorph, Prismasonic, Isco and the rest charge, and that's at one-off "prototype" rates. The actual cost for numbers of these lenses is much less, about a tenth the cost of a Panamorph and a twentieth the cost of an Isco cylindrical. In my opinion, there's a bit of ripping off being perpetrated by the commercial anamorphic lens makers.
One thing that is very important is mounting of the lenses. They have to be spot-on precisely mounted - axes aligned, no tilt, no offset - for best results. This means getting a high quality lens barrel machined to go with the high quality glass. If you skimp on any of this the lens will fail to perform to anywhere near its potential. Prism systems have an advantage over cylindrical lens systems in this regard as they are easier to align.
The optometrist option involved me working out how cylindrical anamorphic lenses work, picking the appropriate diopter lenses that could be made by optometrist supply comanies, and then paying $100 for a set of them. Three days later they arrived, I put them into a cardboard tube, and (after some initial fiddling) they have been working pretty well ever since. There is some chroma fringing but I'm not sure if this is due to my mounting "technique (i.e. the optical axes may not be exactly aligned, and there may be some tilt as well), but the results are very acceptable. A big "wow" factor for the uninitiated who come to my house for a movie. The lenses were not stock focal lengths, so they had to be specially ground for my application. There is an extra charge for this.
There was no refocusing of the projector required either. It's a truly "afocal" system.
I'm not sure if my lens is off-topic or not, as this seems to be a thread about prismatic adapters that are made from scraps of glass, not adapters (like mine) that are ground to a high level of precision i.e. not "DIY", strictly speaking.
Someone upthread mentioned a curved mirror system and asked whether that would work. It will, but you need need mirrors each with a different curve and a method of getting them out of each other's way (not easy, actually). Spacing is of fundamental importance with cylindrical systems (mirrors, refractive lenses) and it is this spacing that usually causes the main mechanical problems. I haven't made a mirror version, but I've modelled it and it would work if I could find someone who could machine the curves accurately enough for me (and they have to be VERY accurate). Once again, not really a DIY process as in "Do It Yourself", more a "Design It Yourself" and then get someone competent (with the right NC tools) to make it for you.
Interestingly, I also designed a glass cylindrical lens with three elements, front, rear and one in the middle for focus correction. These lenses are ground accurate to 0.1 of a millimetre radius in China and are heavier than the plastic optometrist version, but have much less chromatic aberration. They are anti-reflection coated and produce an image 120 inches wide at 15.5 feet that is actually 30% brighter than the "traditional" widescreen method, which is to simply enlarge the picture until it fills the width of the screen (letting the letterbox bands spill off the top and bottom).
With my lenses I use the expansion technique, widening the picture by 1.33. This means I can reduce the height and get a brighter "base" picture to start with. The AR coatings mean I only lose a further 1.8% through the lens on top of the 25% I lose from expansion, of course.
Both vertical compression and horizontal expansion end up with the same final picture brightness. I prefer expansion because it's more convenient when I remove the lens not to have to re-zoom the projector for a smaller screen height.
A note on cost: my custom-ground glass lens sourced from China actually cost a fraction of what Panamorph, Prismasonic, Isco and the rest charge, and that's at one-off "prototype" rates. The actual cost for numbers of these lenses is much less, about a tenth the cost of a Panamorph and a twentieth the cost of an Isco cylindrical. In my opinion, there's a bit of ripping off being perpetrated by the commercial anamorphic lens makers.
One thing that is very important is mounting of the lenses. They have to be spot-on precisely mounted - axes aligned, no tilt, no offset - for best results. This means getting a high quality lens barrel machined to go with the high quality glass. If you skimp on any of this the lens will fail to perform to anywhere near its potential. Prism systems have an advantage over cylindrical lens systems in this regard as they are easier to align.