Hi,
I wanted to ask about what kind of lens would be comparable to my fujinon f1:1.2 lens. I'm looking for around 3'', and would like the lens to give me as much brightness as the fujinon gives me... which bring me to this question, does the less (f:x.xx) give me better brigthness?? I've found some camera lenses, but they are way expensive.... thanks in advance.🙂
I wanted to ask about what kind of lens would be comparable to my fujinon f1:1.2 lens. I'm looking for around 3'', and would like the lens to give me as much brightness as the fujinon gives me... which bring me to this question, does the less (f:x.xx) give me better brigthness?? I've found some camera lenses, but they are way expensive.... thanks in advance.🙂
The f/ number represents the ratio of focal length to iris diameter, so yes, the smaller the number, the greater the light transmission.
You should be able to find a fairly cheap camera lens - look at M42 fitting ones - millions were made, and they're nearly obsolete now, so sell very inexpensively.
You should be able to find a fairly cheap camera lens - look at M42 fitting ones - millions were made, and they're nearly obsolete now, so sell very inexpensively.
Hi,
Thanks for the reply (at last I've got one right !!! 🙂 ) I've been looking around Ebay and the ones I've found are either too small (50mm and below) or have F2.8.... again, I"m just looking for about 3'', I'm using one of those hipgear lcd's. Thanks
Thanks for the reply (at last I've got one right !!! 🙂 ) I've been looking around Ebay and the ones I've found are either too small (50mm and below) or have F2.8.... again, I"m just looking for about 3'', I'm using one of those hipgear lcd's. Thanks
f number
I think the use of f numbers may be misleading when it comes to projection. With a camera, a lower f number means a lens captures a wider arc of the light coming from an object, so it gives you more light on the film. The focal length is included in this f number, because a longer focal length "looks at" the object from a longer distance. So a lens of a specific diameter will gather more light from a near object than another lens of the same diameter but a longer focal length will gather. The photographer uses different iris stops to make the lens effectively have higher f numbers, to enhance the depth of field. Or he can open the iris all the way to defocus things in other planes than the principle object.
But in a projector, all of the light comes from the condensor system. It is in a fixed size cone converging on the projection lens from the whole LCD surface. It would not matter if the lens had a wider diameter (thus a lower f number), since the light would not intersect the outer portions of the lens. In fact, the image would be sharpest if the light was all perfectly converged to a point just at the center of the projection lens. Then the lens would act like an f22+ pinhole, with great depth of field and no distortion at all.
So how wide does the lens have to be? Just a bit wider than your condensor can focus the light at the entrance pupil. Since we tend to use non-adjustable condensors, due to limited choice of fresnel focal lengths, your projector may need a wider lens than another projector with better condensor convergence. On the other hand, if your condensor system puts all the light at the center of the lens, then changing to a wider lens (with the same focal length) will make no difference at all in the image brightness.
I think the use of f numbers may be misleading when it comes to projection. With a camera, a lower f number means a lens captures a wider arc of the light coming from an object, so it gives you more light on the film. The focal length is included in this f number, because a longer focal length "looks at" the object from a longer distance. So a lens of a specific diameter will gather more light from a near object than another lens of the same diameter but a longer focal length will gather. The photographer uses different iris stops to make the lens effectively have higher f numbers, to enhance the depth of field. Or he can open the iris all the way to defocus things in other planes than the principle object.
But in a projector, all of the light comes from the condensor system. It is in a fixed size cone converging on the projection lens from the whole LCD surface. It would not matter if the lens had a wider diameter (thus a lower f number), since the light would not intersect the outer portions of the lens. In fact, the image would be sharpest if the light was all perfectly converged to a point just at the center of the projection lens. Then the lens would act like an f22+ pinhole, with great depth of field and no distortion at all.
So how wide does the lens have to be? Just a bit wider than your condensor can focus the light at the entrance pupil. Since we tend to use non-adjustable condensors, due to limited choice of fresnel focal lengths, your projector may need a wider lens than another projector with better condensor convergence. On the other hand, if your condensor system puts all the light at the center of the lens, then changing to a wider lens (with the same focal length) will make no difference at all in the image brightness.
Thanks for the reply. 🙂
I was doing some testing last night, and came up with couple things... (BTW I"m using a 2.5" lcd and the backlight-still working on my light source) - projected distance 7ft.
- The Fujinon (145mm diameter, f1:1.2) gave me great brightness, sharpness and color; but the picture was reduced about 30''. The lens is right next to the lcd.
- a Bell & Howell 4" f:3.5 coated anastigmat gave me a bigger picture (I think about 50''), but reduced brightness, kinda hard to see at times. The lens is about 1.5-2" from lcd.
- an opaque projector lens (no idea on measurements) gave a reduced picture and had it far from the lcd - so no useable.
Is there a way to find a lens that gives me a nice balance? Thanks for all your help.
I was doing some testing last night, and came up with couple things... (BTW I"m using a 2.5" lcd and the backlight-still working on my light source) - projected distance 7ft.
- The Fujinon (145mm diameter, f1:1.2) gave me great brightness, sharpness and color; but the picture was reduced about 30''. The lens is right next to the lcd.
- a Bell & Howell 4" f:3.5 coated anastigmat gave me a bigger picture (I think about 50''), but reduced brightness, kinda hard to see at times. The lens is about 1.5-2" from lcd.
- an opaque projector lens (no idea on measurements) gave a reduced picture and had it far from the lcd - so no useable.
Is there a way to find a lens that gives me a nice balance? Thanks for all your help.
image brightness
With a 2.5 inch LCD, what you are building is more like a slide projector than a larger-format LCD projector. For the larger format designs we use fresnels to make the light converge toward the projection lens. For your design, your lenses are probably already capturing all the light going through the LCD since they are larger than the LCD. So you don't really need any fresnel condensors.
I think the difference in brightness between your lenses, is just the difference in image size. If you moved the projector back until the Fujinon gave you a 50" image, I bet it would be about the same brightness as the Bell & Howell 50" image. It is just a matter of spreading the same amount of light over more area, so you get fewer lumens per square inch.
I think you need a better lamp!
With a 2.5 inch LCD, what you are building is more like a slide projector than a larger-format LCD projector. For the larger format designs we use fresnels to make the light converge toward the projection lens. For your design, your lenses are probably already capturing all the light going through the LCD since they are larger than the LCD. So you don't really need any fresnel condensors.
I think the difference in brightness between your lenses, is just the difference in image size. If you moved the projector back until the Fujinon gave you a 50" image, I bet it would be about the same brightness as the Bell & Howell 50" image. It is just a matter of spreading the same amount of light over more area, so you get fewer lumens per square inch.
I think you need a better lamp!
Thanks for your input on the lexan and the fl lens issue in both threads. You da man !!! 😎
Regarding my lamp choice..... there are some reasons why I'm going this route. 1) I don't have $200 for a 250w HQI set (yet), and these bulbs are rather cheap. 2) I wanna start with a small setup -this bulbs are small, and the Mh ones are big, sometimes huge + ballast and all that. Again, this is a small screen, so my thoughts are that it might not need as much dispersed light as other setups do -and don't wanna fry the lcd. 3) I've seen other setups that use small dichroic lamps, so I thought I'd give it a try.
I'm trying to keep the setup small, and by having a parallel setup would be easier and smaller: my thoughts were: lamp-lexan-lcd-lens... but I think it would be something like: lamp-heat glass-lexan-lcd-lens... or: lamp-cold mirror-lexan-lcd-lens. Does that make sense? 😕
It's my first step in actually building a DIY projector --> moving from the OHP route (too big). And my dream is that I'll be able to use my projector during daylight (of course not possible with the dichroic lamps). And if this projector works out, I'll be more motivated to move up. Thanks for all the help, and don't stop giving out such grealty needed support !! Thanks.
😀
Regarding my lamp choice..... there are some reasons why I'm going this route. 1) I don't have $200 for a 250w HQI set (yet), and these bulbs are rather cheap. 2) I wanna start with a small setup -this bulbs are small, and the Mh ones are big, sometimes huge + ballast and all that. Again, this is a small screen, so my thoughts are that it might not need as much dispersed light as other setups do -and don't wanna fry the lcd. 3) I've seen other setups that use small dichroic lamps, so I thought I'd give it a try.
I'm trying to keep the setup small, and by having a parallel setup would be easier and smaller: my thoughts were: lamp-lexan-lcd-lens... but I think it would be something like: lamp-heat glass-lexan-lcd-lens... or: lamp-cold mirror-lexan-lcd-lens. Does that make sense? 😕
It's my first step in actually building a DIY projector --> moving from the OHP route (too big). And my dream is that I'll be able to use my projector during daylight (of course not possible with the dichroic lamps). And if this projector works out, I'll be more motivated to move up. Thanks for all the help, and don't stop giving out such grealty needed support !! Thanks.
😀
Guy, I have to disagree with your analysis of the importance of aperture.
If you are correct, why have 35mm projectors almost always had f/2.8 or wider lenses, even when these were difficult to calculate and expensive to produce?
Indeed, why not use an actual pinhole, which, if carefully made in suitable material, is capable of very respectable results, and costs *much* less than a decent lens.
I have seen a top quality, high transmission factor, 35mm movie projection lens with a front element around 14" diameter - that's an expensive lens! If your theory worked, wouldn't it be a lot easier and cheaper to use, say, an f/8 lens, and pay careful attention to the condensers instead?
Even if you were correct, a multi-element lens has an optical centre (of sorts), but the size of the elements in front of and behind this point would still affect the transmission of the assembly.
If you are correct, why have 35mm projectors almost always had f/2.8 or wider lenses, even when these were difficult to calculate and expensive to produce?
Indeed, why not use an actual pinhole, which, if carefully made in suitable material, is capable of very respectable results, and costs *much* less than a decent lens.
I have seen a top quality, high transmission factor, 35mm movie projection lens with a front element around 14" diameter - that's an expensive lens! If your theory worked, wouldn't it be a lot easier and cheaper to use, say, an f/8 lens, and pay careful attention to the condensers instead?
Even if you were correct, a multi-element lens has an optical centre (of sorts), but the size of the elements in front of and behind this point would still affect the transmission of the assembly.
cheap MH bulbs
Here is a link to goodmart.com:
http://www.goodmart.com/products/Tubular_Metal_Halide_Lamp.htm
They have a lot of less expensive bulbs and ballasts. For example, they have a 250 Watt bulb for $21.33 and matching ballast kit for $45.36 US, plus shipping.
These tend to be bulbs with the standard color temperature of 4200 K, but they certainly are cheap!
I don't think that you use a lower wattage lamp because you have a smaller LCD to illuminate. I think you need enough lumens per square foot of final image, so the LCD size is not as important as the final image size. But you may run into a heat problem when you try to get all of that light through a small LCD: Compare the area of a 2.5" LCD to the area of a 15" LCD. You would be putting 36 times as many lumens per square inch through your 2.5" LCD, compared to a 15" LCD, to get the same number of lumens on the screen.
Maybe you should just try for a smaller image.
Here is a link to goodmart.com:
http://www.goodmart.com/products/Tubular_Metal_Halide_Lamp.htm
They have a lot of less expensive bulbs and ballasts. For example, they have a 250 Watt bulb for $21.33 and matching ballast kit for $45.36 US, plus shipping.
These tend to be bulbs with the standard color temperature of 4200 K, but they certainly are cheap!
I don't think that you use a lower wattage lamp because you have a smaller LCD to illuminate. I think you need enough lumens per square foot of final image, so the LCD size is not as important as the final image size. But you may run into a heat problem when you try to get all of that light through a small LCD: Compare the area of a 2.5" LCD to the area of a 15" LCD. You would be putting 36 times as many lumens per square inch through your 2.5" LCD, compared to a 15" LCD, to get the same number of lumens on the screen.
Maybe you should just try for a smaller image.
Hi,
The price I was quoting was a self aproximation of this + shipping. Thanks for the heads up about the prices...
About screen size.... I just wanna be able to project on my full lenticular screen (I think it's either 60'' or 70'') or on my 50''x50'' blackout cloth.
so, even if I used the cold mirror and the lexan, would I still be having heat problems (using fans also of course)? what about distances? I would like to keep my setup under 10''x6''x6''....
Thanks for your support guys !! It's really getting me pumped up, kinda like Hans and Frans.... SNL (never mind).
Please keep guiding me in the right direction fellers !!!
The price I was quoting was a self aproximation of this + shipping. Thanks for the heads up about the prices...
About screen size.... I just wanna be able to project on my full lenticular screen (I think it's either 60'' or 70'') or on my 50''x50'' blackout cloth.
so, even if I used the cold mirror and the lexan, would I still be having heat problems (using fans also of course)? what about distances? I would like to keep my setup under 10''x6''x6''....
Thanks for your support guys !! It's really getting me pumped up, kinda like Hans and Frans.... SNL (never mind).
Please keep guiding me in the right direction fellers !!!
cold mirror
The 4.75" diameter cold mirror I got from surplusshed.com for $5 works very well. I think you will not have a heat problem if you can reflect your light from one of these cold mirrors. Since you are trying to light a small LCD with a wide parallel beam, that size cold mirror should fit perfectly. Put a black metal heat sink an inch behind the cold mirror to absorb the short-wave IR and re-emit it as heat. The heat sink will get hot, so it needs some fan air.
With this design, you should be able to make a very small box: You have no condensor or lower fresnel, so you don't have to put the lamp at the lower fresnel focal length. And you are using a wide diameter slide projector lens with a very short back focal length, so you don't need to have space for an upper fresnel focal length, either. What you are making, is essentially a slide projector. It will not have to be any larger than a commercial unit, except you should have a long enough path from the lamp to the LCD so you can fit the 45 degree angle cold mirror. If the lamp beam spreads to be too large over than distance, then you could get a bit more light through the LCD by adding a very weak condensor lens to converge the cone of light a bit. You could try a lens from a pair of reading glasses for that, if you have access to some different strengths.
If you change to an omni-directional MH lamp at some time in the future, then you would want to add a spherical reflector and a condensor lens so you could get more light heading toward the LCD.
The 4.75" diameter cold mirror I got from surplusshed.com for $5 works very well. I think you will not have a heat problem if you can reflect your light from one of these cold mirrors. Since you are trying to light a small LCD with a wide parallel beam, that size cold mirror should fit perfectly. Put a black metal heat sink an inch behind the cold mirror to absorb the short-wave IR and re-emit it as heat. The heat sink will get hot, so it needs some fan air.
With this design, you should be able to make a very small box: You have no condensor or lower fresnel, so you don't have to put the lamp at the lower fresnel focal length. And you are using a wide diameter slide projector lens with a very short back focal length, so you don't need to have space for an upper fresnel focal length, either. What you are making, is essentially a slide projector. It will not have to be any larger than a commercial unit, except you should have a long enough path from the lamp to the LCD so you can fit the 45 degree angle cold mirror. If the lamp beam spreads to be too large over than distance, then you could get a bit more light through the LCD by adding a very weak condensor lens to converge the cone of light a bit. You could try a lens from a pair of reading glasses for that, if you have access to some different strengths.
If you change to an omni-directional MH lamp at some time in the future, then you would want to add a spherical reflector and a condensor lens so you could get more light heading toward the LCD.
"You could try a lens from a pair of reading glasses for that, if you have access to some different strengths."
you mean reading glasses like the ones you find at Walmart and such? What kind of strenght should I use for better brigthness?
another BIG concern that I have (BTW) is the LCD ribbon cable... I really don't wanna screw it... how do I do to keep it from tearing (reinforcing)?
Man, I'm learning so much !!! Thanks a lot !!
you mean reading glasses like the ones you find at Walmart and such? What kind of strenght should I use for better brigthness?
another BIG concern that I have (BTW) is the LCD ribbon cable... I really don't wanna screw it... how do I do to keep it from tearing (reinforcing)?
Man, I'm learning so much !!! Thanks a lot !!
Reading glasses
Reading glasses are just a cheap way to find a weak positive meniscus lens of the right focal length. Especially if WalMart or the drug store will let you take them back or exchange them for another weaker or stronger pair. They are rated by Diopters, where:
Diopters = 1000 / focal length in mm
So a 1.0 Diopter lens has a focal length of 1000 mm. A 2.0 has a focal length of 500 mm, etc.
I suggested a weak positive lens, if the beam between your dicroic reflector lamp and the LCD is spreading too much. Putting the lens near the lamp would converge the beam. It would be acting as a weak condensor lens. A 1 Diopter lens would make a parallel beam focus on a point 1000 mm from the lens. So it will make a beam that is diverging two inches over 1 meter distance, into a parallel beam. You can see that this is not much refraction. Reading glasses come in many strengths from 1.0 up to 5.0, so that gives you a lot of different lenses to try for free!
Regarding the flexible printed connector cables, I would mount the LCD and the controller boards in a rigid frame, so those cables are held in one position without any stress. I made something like a picture frame out of aluminum and wood. The LCD fits into the frame and is held in place securely. The PC boards are flopped over about 150 degrees from their normal position behind the backlight. Then they are held against small angled blocks of wood with tiny screws and rubber washers. The flex cables are under no stress at all. The boards stand up less than 1" above the surface of the LCD.
For a design that uses fresnel lenses to converge light at the projector lens:
If you are planning to use a mirror after the LCD, or a split fresnel design, then you need to move the PC boards pretty much out of the way. With a mirror, the LCD will have light moving from the back to the front, and you have to get the lower fresnel tray close enough to the LCD. With a split fresnel design, you need fresnel trays on both side of the LCD and you don't want either tray hitting the PC boards. If you will not use a mirror and both fresnels will be under the LCD, then you could mount the PC boards at a 90 degree angle from their normal position, since the light will then go from front to back of the LCD.
But I have seen pictures of many LCD frames where the boards are flopped over 180 degrees and screwed down to the frame surface. The point is to get them all mounted securely as soon as possible, so you don't keep flexing the cables or accidently tear a cable off the LCD or board.
Reading glasses are just a cheap way to find a weak positive meniscus lens of the right focal length. Especially if WalMart or the drug store will let you take them back or exchange them for another weaker or stronger pair. They are rated by Diopters, where:
Diopters = 1000 / focal length in mm
So a 1.0 Diopter lens has a focal length of 1000 mm. A 2.0 has a focal length of 500 mm, etc.
I suggested a weak positive lens, if the beam between your dicroic reflector lamp and the LCD is spreading too much. Putting the lens near the lamp would converge the beam. It would be acting as a weak condensor lens. A 1 Diopter lens would make a parallel beam focus on a point 1000 mm from the lens. So it will make a beam that is diverging two inches over 1 meter distance, into a parallel beam. You can see that this is not much refraction. Reading glasses come in many strengths from 1.0 up to 5.0, so that gives you a lot of different lenses to try for free!
Regarding the flexible printed connector cables, I would mount the LCD and the controller boards in a rigid frame, so those cables are held in one position without any stress. I made something like a picture frame out of aluminum and wood. The LCD fits into the frame and is held in place securely. The PC boards are flopped over about 150 degrees from their normal position behind the backlight. Then they are held against small angled blocks of wood with tiny screws and rubber washers. The flex cables are under no stress at all. The boards stand up less than 1" above the surface of the LCD.
For a design that uses fresnel lenses to converge light at the projector lens:
If you are planning to use a mirror after the LCD, or a split fresnel design, then you need to move the PC boards pretty much out of the way. With a mirror, the LCD will have light moving from the back to the front, and you have to get the lower fresnel tray close enough to the LCD. With a split fresnel design, you need fresnel trays on both side of the LCD and you don't want either tray hitting the PC boards. If you will not use a mirror and both fresnels will be under the LCD, then you could mount the PC boards at a 90 degree angle from their normal position, since the light will then go from front to back of the LCD.
But I have seen pictures of many LCD frames where the boards are flopped over 180 degrees and screwed down to the frame surface. The point is to get them all mounted securely as soon as possible, so you don't keep flexing the cables or accidently tear a cable off the LCD or board.
"Putting the lens near the lamp would converge the beam"
Do you know how much heat do these lenses take? I'm afraid I'll make it explode if it's too close or has too much heat...
I am waitning on my cold mirror from surplus shed... I went ahead and got the hot mirror just to see how it works.
I think I'll have to hurry up with this... my OHP is acting weird... it burnt 2 lamps with no apparent reason!! I thought the lamp had died... so I chenged... and when I turned it on, it popped the inner coil... tried the other lamp... same thing. What wrong, the bulbs or the OHP??
Thanks !!!
Do you know how much heat do these lenses take? I'm afraid I'll make it explode if it's too close or has too much heat...
I am waitning on my cold mirror from surplus shed... I went ahead and got the hot mirror just to see how it works.
I think I'll have to hurry up with this... my OHP is acting weird... it burnt 2 lamps with no apparent reason!! I thought the lamp had died... so I chenged... and when I turned it on, it popped the inner coil... tried the other lamp... same thing. What wrong, the bulbs or the OHP??
Thanks !!!
lens near the lamp might burn
Good point. A glass lens would be much better than an acrylic lens for this! You could use either one for a quick experiment as I suggested, trying different strengths and taking them back for exchange at the store until you find the right strength. Once you know what lens you need, then you could get one that is made from glass, or even pyrex if it gets very hot. Reading glasses are just a good way to try a lot of different strength lenses at no cost, before you buy a real uncut round lens of the correct strength and size.
About those OHP bulbs that burned out immediately: Did you touch them with your bare fingers? Some bulbs (especially halogen) will pop if there is a fingerprint on the outer glass. The fingerprint absorbs so much heat that the outer glass expands unevenly and cracks.
Good point. A glass lens would be much better than an acrylic lens for this! You could use either one for a quick experiment as I suggested, trying different strengths and taking them back for exchange at the store until you find the right strength. Once you know what lens you need, then you could get one that is made from glass, or even pyrex if it gets very hot. Reading glasses are just a good way to try a lot of different strength lenses at no cost, before you buy a real uncut round lens of the correct strength and size.
About those OHP bulbs that burned out immediately: Did you touch them with your bare fingers? Some bulbs (especially halogen) will pop if there is a fingerprint on the outer glass. The fingerprint absorbs so much heat that the outer glass expands unevenly and cracks.
I don't think I touched it... I'm fairly careful with bulbs... I use them quite often for my classroom OHP, and never had this problem before... it seems like the coil just came loose... I mean, you shake it and it sounds like a rattle.... 
I'll have to contact maintenance to check it or get a new one... but that's another story.
Also, you mentioned a black heatsink behind the cold mirror... does it have to be black? I've got a blue one... might work the same way, but just wanted to check with DA MASTER... 😎
Thanks !!
I'll have to contact maintenance to check it or get a new one... but that's another story.
Also, you mentioned a black heatsink behind the cold mirror... does it have to be black? I've got a blue one... might work the same way, but just wanted to check with DA MASTER... 😎
Thanks !!
DA Master?
Thanks, but you give me way too much credit. Lots of other people on this forum have way more experience with projectors. I just report things I've tried or read about. A lot of it is from other engineering projects not connected with projectors.
A blue heatsink is probably okay too. Black just absorbs more energy. Flat black paint is good, but black anodized aluminum is better. The best is carbon black, but that can be messy. If your blue paint is shiny, you might want to sand it a bit to make it dull.
The point is: Don't put it right up against the back of the cold mirror. That would heat the mirror glass and make it emit long-wave IR out the front. Put the heatsink at least an inch beyond the back of the cold mirror, with some cooling air blowing between them. The heatsink will absorb the short-wave IR and that energy will be carried away by the cooling air. Then the cold mirror will stay "cold".
Thanks, but you give me way too much credit. Lots of other people on this forum have way more experience with projectors. I just report things I've tried or read about. A lot of it is from other engineering projects not connected with projectors.
A blue heatsink is probably okay too. Black just absorbs more energy. Flat black paint is good, but black anodized aluminum is better. The best is carbon black, but that can be messy. If your blue paint is shiny, you might want to sand it a bit to make it dull.
The point is: Don't put it right up against the back of the cold mirror. That would heat the mirror glass and make it emit long-wave IR out the front. Put the heatsink at least an inch beyond the back of the cold mirror, with some cooling air blowing between them. The heatsink will absorb the short-wave IR and that energy will be carried away by the cooling air. Then the cold mirror will stay "cold".
You might be right, but newbies like us really appreciate the help of those that have the knowledge and are willing to put it in idiot-proof terms and share it with us, and not like others that are (or may think are) too cool for us and won't even bother, you know?
You said you worked for Conexant? I've recently got me a WinTV card, and it's got a conexant chip on it...
Thanks !
You said you worked for Conexant? I've recently got me a WinTV card, and it's got a conexant chip on it...
Thanks !
Got 'em!
I got my cold & hot mirror on the mail yesterday... man, that's what I call fast shipping !!
Anyway, I did some more testing with 2 other lenses I bought. one is a dukane 3'' f4.5 (probably from a 16mm film projector), and the other is a kowa fl 112mm f4.5 copy lens.
I used an 4'' LCD monitor from my daughter's video set, so light source is the backlight. I used my lenticular screen at 70'' (56''x42'' which makes it 4:3).
Fujinon 145mm f1:1.2
lens right next to the lcd and covered 70'' at 100'' away -- After that it started to lose focus even with the screen right next to the lcd. Though it has the best brightness I've seen, pretty good for a backlight light source.
Kowa copy lens
lens was about 5 inches from the lcd and covered 70'' at 74'' away -- good focus and medium brightness, not as great as the fujinon.
Dukane film lens
lens was about 1.5'' from the lcd and covered 70'' at 64'' away. This one gave me the biggest icture with short throw. Then of course it's designed for a 3'', so it didn't cover all the lcd screen, but was impressed with the magnification power and the brigthness was decent.
Bell & Howell 4'' anastigmat f3.5
lense was about 1.5'' from lcd, and covered 70'' at 84'' away. Brigthness suffered with this one, but seems to be a pretty good and sturdy lens.
SO guys, which one would be the better choice? I'm thinking about using the dukane one... I'll definitely use the fujinon in another project with a biger lcd like the one with leds... what factor should I take into account before starting out? light output, how far from screen it'll be..... I'll be putting more time on it as soon as I'm done with all this workload (final projects, term papers, final exams, etc, etc etc....
😕 I need your input here, thanks in advance.
P.S. BTW, the screen was not of great quality or resolution, however, the screendoor was not greatly noticeable... would it be the projecting size or the screen?
I got my cold & hot mirror on the mail yesterday... man, that's what I call fast shipping !!
Anyway, I did some more testing with 2 other lenses I bought. one is a dukane 3'' f4.5 (probably from a 16mm film projector), and the other is a kowa fl 112mm f4.5 copy lens.
I used an 4'' LCD monitor from my daughter's video set, so light source is the backlight. I used my lenticular screen at 70'' (56''x42'' which makes it 4:3).
Fujinon 145mm f1:1.2
lens right next to the lcd and covered 70'' at 100'' away -- After that it started to lose focus even with the screen right next to the lcd. Though it has the best brightness I've seen, pretty good for a backlight light source.
Kowa copy lens
lens was about 5 inches from the lcd and covered 70'' at 74'' away -- good focus and medium brightness, not as great as the fujinon.
Dukane film lens
lens was about 1.5'' from the lcd and covered 70'' at 64'' away. This one gave me the biggest icture with short throw. Then of course it's designed for a 3'', so it didn't cover all the lcd screen, but was impressed with the magnification power and the brigthness was decent.
Bell & Howell 4'' anastigmat f3.5
lense was about 1.5'' from lcd, and covered 70'' at 84'' away. Brigthness suffered with this one, but seems to be a pretty good and sturdy lens.
SO guys, which one would be the better choice? I'm thinking about using the dukane one... I'll definitely use the fujinon in another project with a biger lcd like the one with leds... what factor should I take into account before starting out? light output, how far from screen it'll be..... I'll be putting more time on it as soon as I'm done with all this workload (final projects, term papers, final exams, etc, etc etc....
😕 I need your input here, thanks in advance.
P.S. BTW, the screen was not of great quality or resolution, however, the screendoor was not greatly noticeable... would it be the projecting size or the screen?
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