~48,5cm x ~34cm with 0,1mm groove pitch
Hello.
Does it need more height for a key keystone-correction?
If I tilt the Fresnel horizontal, the height becomes less.
Therefore it should have also more height for a good keystone-correction.
A square Fresnel would be good for a good keystone-correction.
How much keystone-correction (angle) is maximum possible?
I want to buy a 15,4"-tft (1920x1200) with 16:10. Those have approx. 331,6mm x 207,1mm. The Fresnel lens must be larger than the TFT. It must be pushed still into a support rail at the sides. On the right and left side is 1,5cm more good.
And at the top an bottom side more for the keystone-correction. I don't know what the maximum possible keystone. Know you it?
When you look from the front on a sqaure (the TFT) and you tilt the square over the horizontal (for the keystone-correction) the square will became a smaller height.
When you make one Fresnel for 15"/4:3-TFTs with 305mm x 230mm and 15,4"/16:10-TFTs with 331,6mm x 207,1mm you can take 331,6mm x 230mm.
For a max. 45°-Keystone (is this possible?) the hight must be 311,7mm and 3cm for the Frame/addition (2 x 1,5cm) = 341,7mm for the same height as without tilting.
The mass for a universal 15"/15,4"-Fresnellens for a big horizontal keystone-corection would be 361,6xmm x 341,7xmm.
For a two-axle 45°-solution would be the mass 484,7mm x 341,7mm
Ist the fine groove pitch better for high resolution (like 1920x1200)? Then i prefer the finest groove pitch.
And for my "Mega-Keystone" (when it works) I think a fine groove pitch is better.
You can cut it down to your prefered size.
I think you mean not "1mm groove pitch" ;-) .....
Me too 🙂 .....
Greetings,
Tobias Claren
jimhuang said:
Hello.
Does it need more height for a key keystone-correction?
If I tilt the Fresnel horizontal, the height becomes less.
Therefore it should have also more height for a good keystone-correction.
A square Fresnel would be good for a good keystone-correction.
How much keystone-correction (angle) is maximum possible?
I want to buy a 15,4"-tft (1920x1200) with 16:10. Those have approx. 331,6mm x 207,1mm. The Fresnel lens must be larger than the TFT. It must be pushed still into a support rail at the sides. On the right and left side is 1,5cm more good.
And at the top an bottom side more for the keystone-correction. I don't know what the maximum possible keystone. Know you it?
When you look from the front on a sqaure (the TFT) and you tilt the square over the horizontal (for the keystone-correction) the square will became a smaller height.
When you make one Fresnel for 15"/4:3-TFTs with 305mm x 230mm and 15,4"/16:10-TFTs with 331,6mm x 207,1mm you can take 331,6mm x 230mm.
For a max. 45°-Keystone (is this possible?) the hight must be 311,7mm and 3cm for the Frame/addition (2 x 1,5cm) = 341,7mm for the same height as without tilting.
The mass for a universal 15"/15,4"-Fresnellens for a big horizontal keystone-corection would be 361,6xmm x 341,7xmm.
For a two-axle 45°-solution would be the mass 484,7mm x 341,7mm
Ist the fine groove pitch better for high resolution (like 1920x1200)? Then i prefer the finest groove pitch.
And for my "Mega-Keystone" (when it works) I think a fine groove pitch is better.
With 48,5cm x 34cm we have enough space for fpr a 15,4"-TFT (1920x1200) with a Mega-Keystone or all other Displays with a normal Kestone.jdevo2004 said:
You can cut it down to your prefered size.
I think you mean not "1mm groove pitch" ;-) .....
videoman said:
Me too 🙂 .....
Greetings,
Tobias Claren
jimhuang said:
600mm FL would be better. (we can move LCD near objectice). Jimhuang, when we can send our orders? thanks, David.
Update on new fresnel. 3Dlens.com has stated it will be ready the end of this month. Pricing is set at U.S.$28.
I've been lurking DIY PJ forums for a while and trying to absorb info. I'm not sure if I understand what this lens will solve - will this lens solve the problem of focus and light problems in the corners of the image for larger panels?
TIA
TIA
good point 😀
some people believe it will. (I am not one of them 😀)
the lens was designed from the well known 135 triplet (450mm focal), so I wonder, will 3dlens make a new lens if another proyection lens is needed?
maybe we precipitated on the "ideal lens". We will see it soon i Believe. Is it any 135 triplet owner that is waiting for the lens?
some people believe it will. (I am not one of them 😀)
the lens was designed from the well known 135 triplet (450mm focal), so I wonder, will 3dlens make a new lens if another proyection lens is needed?
maybe we precipitated on the "ideal lens". We will see it soon i Believe. Is it any 135 triplet owner that is waiting for the lens?
This fresnel lens was designed with longer throw optics in mind. To move the projector farther back from the screen longer focal length fresnels and triplets are needed. Wether or not this specific 135 triplet can focus on a panel bigger than 15 inches, testing will tell. Any triplet in the 450mm range will work with this fresnel. The size of panel a triplet can focus on will be determined by its field of view. This all began with people wanting longer throw optics so they could move their projectors behind their seating area. I personally would like to thank Jim Huang of 3Dlens.com for coming forward and providing the diy community with a fresnel lens so we can move forward in this direction.
I'm one of them. After failing with the 330mm fresnel and 135mm pj lens,i'm desperately waiting for this fresnel since ever. we'll see to it.
Question is: Will I have to buy 2 of these 550mm fresnels, or use one 550 for the front and a 330 for the rear fresnel. I am assuming this new fresnel will aleviate the hot spot in the middle of my screen.
mmm, let me tell you the ideal field fresnell lens was designed exclusivelly considering the 135 triplet mikey, check it on the previows pages...
It was explayned something like this; we already have a 17" screen a 135 triplet... we would like to have 100" diagonal so what wouod be the best field fresnell?... (answer; 550mm)
that was the starting point (I never accepted it anyway).
So vguys, would you take the challence on testing it for all of us? (I mean do you mind posting resulst for everybody here for instance?)
It was explayned something like this; we already have a 17" screen a 135 triplet... we would like to have 100" diagonal so what wouod be the best field fresnell?... (answer; 550mm)
that was the starting point (I never accepted it anyway).
So vguys, would you take the challence on testing it for all of us? (I mean do you mind posting resulst for everybody here for instance?)
Rox, this is all about longer throw optics. Your personal views on the 135mm triplet are well known on this and other forums.🙂
I agreed,lolMikey p said:
I'll post the result ASA i 'm done with it. I still had the box and every but the fresnel and another LCD(I've broke my dell1704 accidentally by free fall ).
ok, lets say it was originally designed for 450mm focal projection lenses (but we are not talking about the 135 triplet 😀 😀)
just one 550 fresnel
jdevo2004: No, you just need one of these 550 mm fl fresnels to use as the field fresnel (the second one) to match the LCD to lens distance of a 450 mm fl projection lens. For the condensor fresnel (the first one) you can use a 200 to 220 mm fl fresnel, with the lamp arc to fresnel distance equal to the fresnel's focal length.
In spite of what Rox has to say, there are lenses with focal lengths around 450 mm, that have huge Field Of View. For example, lots of 450 mm fl process lenses can make perfect exposures on 11" by 14" photographic plates. And those are with the lens focussed at an infinite distance, so the lens to plate distance really is 450 mm. We never put the screen much more than 20 feet away, so our LCD to lens distance is much longer than 450 mm. This helps the FOV even more.
Imagine a 11" by 14" LCD: That would be 17.8" diagonal! And then by using a 503 mm LCD to lens distance (correct for 14 foot throw distance), instead of 450 mm, that would increase the diagonal FOV to a 19.9" diagonal LCD.
The problem with most process lenses is that they are relatively small diameter (ie. 60 - 80 mm), so some of the light from a large arc lamp is lost. There are two possible solutions for that:
1) Use a small arc lamp, so the correct fresnels (e.g. 550 mm field fresnel) can direct all of the light to the small process lens.
2) Get a custom triplet made that is like a wide FOV process lens, but scaled-up to 125 mm diameter.
jdevo2004: No, you just need one of these 550 mm fl fresnels to use as the field fresnel (the second one) to match the LCD to lens distance of a 450 mm fl projection lens. For the condensor fresnel (the first one) you can use a 200 to 220 mm fl fresnel, with the lamp arc to fresnel distance equal to the fresnel's focal length.
In spite of what Rox has to say, there are lenses with focal lengths around 450 mm, that have huge Field Of View. For example, lots of 450 mm fl process lenses can make perfect exposures on 11" by 14" photographic plates. And those are with the lens focussed at an infinite distance, so the lens to plate distance really is 450 mm. We never put the screen much more than 20 feet away, so our LCD to lens distance is much longer than 450 mm. This helps the FOV even more.
Imagine a 11" by 14" LCD: That would be 17.8" diagonal! And then by using a 503 mm LCD to lens distance (correct for 14 foot throw distance), instead of 450 mm, that would increase the diagonal FOV to a 19.9" diagonal LCD.
The problem with most process lenses is that they are relatively small diameter (ie. 60 - 80 mm), so some of the light from a large arc lamp is lost. There are two possible solutions for that:
1) Use a small arc lamp, so the correct fresnels (e.g. 550 mm field fresnel) can direct all of the light to the small process lens.
2) Get a custom triplet made that is like a wide FOV process lens, but scaled-up to 125 mm diameter.
Guy et al,
Where can I get one of these projection lenses that have the huge FOV that you mentioned for something like a 15.4" 16:10 panel or even larger? The only sources I know of are Lumenlab and diyprojectorcompany.
For the two points you mentioned:
1). Would the short arc lamp 18wheeler has acquired be something like you mentioned?
2). How feasible is it for a DIY to get a custom triplet made? Where would one do this?
Where can I get one of these projection lenses that have the huge FOV that you mentioned for something like a 15.4" 16:10 panel or even larger? The only sources I know of are Lumenlab and diyprojectorcompany.
For the two points you mentioned:
1). Would the short arc lamp 18wheeler has acquired be something like you mentioned?
2). How feasible is it for a DIY to get a custom triplet made? Where would one do this?
short arc lamp or custom lens
If you look around in the forum, there are threads on both topics. Like you mentioned, there is a group buy on short-arc lamps. They are unusually cheap for such lamps, too. The only problem is that they have a much shorter life than the 20-25 mm arc lamps we have been using.
In other threads there have been some investigations of making custom projection lenses. So far, it looks like about $500 each for a run of 100! Ouch! That is why everybody is willing to spend some money to try surplus lens alternatives. (It might be better if we could find a lens grinder in Mexico, India, or China.)
My example of a flawless wide FOV lens is a 600 mm fl 85 mm diameter Rodenstock APO Ronar process lens I got on eBay for $280. I see other process lenses there on occasion. The 450 mm fl lenses go for less, since they are still being made. A process lens, short-arc lamp, and 550 mm fl field fresnel should work together VERY well, but all I have right now is the lens. I will get one of the 550 mm fl fresnels as soon as they are available. Then maybe I will try a short-arc, to see if the combination of the three lives up to its potential.
If you look around in the forum, there are threads on both topics. Like you mentioned, there is a group buy on short-arc lamps. They are unusually cheap for such lamps, too. The only problem is that they have a much shorter life than the 20-25 mm arc lamps we have been using.
In other threads there have been some investigations of making custom projection lenses. So far, it looks like about $500 each for a run of 100! Ouch! That is why everybody is willing to spend some money to try surplus lens alternatives. (It might be better if we could find a lens grinder in Mexico, India, or China.)
My example of a flawless wide FOV lens is a 600 mm fl 85 mm diameter Rodenstock APO Ronar process lens I got on eBay for $280. I see other process lenses there on occasion. The 450 mm fl lenses go for less, since they are still being made. A process lens, short-arc lamp, and 550 mm fl field fresnel should work together VERY well, but all I have right now is the lens. I will get one of the 550 mm fl fresnels as soon as they are available. Then maybe I will try a short-arc, to see if the combination of the three lives up to its potential.
mmm i would say considering the 280$ second hand source on ebay isn´t the way diycomynity should go. We need a part source... there is a 135 triplet source available... but i don´t see another source for onother 450mm focal (wider fov) lens...
and by the way, i find 280$ not compatible with DIY philosofy.
and by the way, i find 280$ not compatible with DIY philosofy.
$280 is quite steep compared to the other projection lenses, but the overall cost is of a project would still be much less than a commercial projector. Besides, part of the DIY philosophy is to work with what you can find, right? This type of lens is just another option.
I tried looking on ebay for a similar "process lens." What exactly is a process lens? I also tried searching on the brand Rodenstock. I take it that these are photo lenses? What spec's - aperture and EFL - should I look for if I was to use the lens with the upcoming 550 mm fl fresnel?
I tried looking on ebay for a similar "process lens." What exactly is a process lens? I also tried searching on the brand Rodenstock. I take it that these are photo lenses? What spec's - aperture and EFL - should I look for if I was to use the lens with the upcoming 550 mm fl fresnel?
Rox said:
look out, the diy community police are telling you what you should or should not do. 😱
I have 2 long focal length, large format lenses (457mm, 480mm) that I have bought from ebay and I can't wait for the 550 fresnels lense to try them out. This is what DIY is about. Finding what works best for you no matter your budget maybe. Maybe ROX is a little biased considering the help he has given to re-engineer the Pro Lense from LL?
and by the way, I find Rox's comment not compatible with DIY philosphy.
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