I thought I was lucky yesterday when a friend gave me a non working 17" HP. I'm assembling parts for my first projector and figured I just saved myself some serious cash (yes, I believe I have it working.) The LCD stripped easily, and I figured I was well on my way to the land of DIY projection.
Then I realized that all of my plans had been for a 15" LCD. From what I've read after searching, 17" requires a lot of cash for different lenses. I am not interested in having out of focus corners, so it seems the 80mm triplet from DIYPC is out. the 135mm is a little pricey for me, so I started looking at copy lenses via Surplus Shed. I've found one (I think) and plugged it into the calculator at DIYPC. Here's what it spit back:
Projection Size: 120"
Lens Focal Length: 137mm
LCD: 17"
Throw Distance: 43.499" ?!?!?!?!?
This seems very wrong. I'm guessing I just have the wrong lens? Can anyone verify this or recommend a different (affordable) option?
Then I realized that all of my plans had been for a 15" LCD. From what I've read after searching, 17" requires a lot of cash for different lenses. I am not interested in having out of focus corners, so it seems the 80mm triplet from DIYPC is out. the 135mm is a little pricey for me, so I started looking at copy lenses via Surplus Shed. I've found one (I think) and plugged it into the calculator at DIYPC. Here's what it spit back:
Projection Size: 120"
Lens Focal Length: 137mm
LCD: 17"
Throw Distance: 43.499" ?!?!?!?!?
This seems very wrong. I'm guessing I just have the wrong lens? Can anyone verify this or recommend a different (affordable) option?
No that sounds about right. The FL of the copy lens is VERY short. I have a 17" LCD and my projection lens has a FL of 457mm. You'll need something around 400mm - 600mm if you want to place the projector in the back of the room and not have a 30ft picture.
Copy lenses might work, but often times their apature is too small (hence a dimmer picture). You either need to find a "golden" copy lens (wide apature / long focal length) or bite the bullet and get the Pro lens from LL if you want a razor sharp screen with a 17" LCD.
The only other option I've seen that could potentially project a 17" LCD with a razor sharp picture is a 22" opaque projection lens. Do a search on here for that.
Copy lenses might work, but often times their apature is too small (hence a dimmer picture). You either need to find a "golden" copy lens (wide apature / long focal length) or bite the bullet and get the Pro lens from LL if you want a razor sharp screen with a 17" LCD.
The only other option I've seen that could potentially project a 17" LCD with a razor sharp picture is a 22" opaque projection lens. Do a search on here for that.
Just so I might understand:
So I can get away with putting the projector on the floor in front of my couch and adjusting for keystoning? Or would the key stone effect be too great at 4 feet away? I have no problem sitting behind the projector if I can get away with using this ridiculously cheap lens.
Here's the rest of the lens specs listed:
"The assembly is 55mm diameter and 50mm long with a clear lens diameter of 37mm. The focal length is 137mm."
So I can get away with putting the projector on the floor in front of my couch and adjusting for keystoning? Or would the key stone effect be too great at 4 feet away? I have no problem sitting behind the projector if I can get away with using this ridiculously cheap lens.
Here's the rest of the lens specs listed:
"The assembly is 55mm diameter and 50mm long with a clear lens diameter of 37mm. The focal length is 137mm."
Well, yes and no. The keystoning would probably be too great. Probably talking angles greater than 30 degrees. If you angled the screen downward, you might be able to compensate for the extreme keystone.
35mm lens diameter is REALLY small. Unless you have a bulb with an arc width in the single digits (1mm - 9mm).... The Ushio 400W (the one many people use here) has an arc length of 27mm. You can get smaller arc lengths, but they cost A LOT more. It'd probably balance out the savings you get by using less expensive lens. You'll probably lose a significant amount of light by using that lens. Also, you'd have to find a fresnel lens to match up to that lens. The 220mm might work. The 200mm might work. Depends on your calcs.
I'm not saying don't try it, but you might find your picture too dim and the fresnels hard to find. My advice, keep looking for a better lens. 🙂 Good luck!
35mm lens diameter is REALLY small. Unless you have a bulb with an arc width in the single digits (1mm - 9mm).... The Ushio 400W (the one many people use here) has an arc length of 27mm. You can get smaller arc lengths, but they cost A LOT more. It'd probably balance out the savings you get by using less expensive lens. You'll probably lose a significant amount of light by using that lens. Also, you'd have to find a fresnel lens to match up to that lens. The 220mm might work. The 200mm might work. Depends on your calcs.
I'm not saying don't try it, but you might find your picture too dim and the fresnels hard to find. My advice, keep looking for a better lens. 🙂 Good luck!
Yes you can. It's actually a great lens if you don't mind the slightly out of focus corners. If you're interested, I used an 18" Beseler and a 17" LCD on my projector:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=69975
http://www.diyaudio.com/forums/showthread.php?s=&threadid=69975
No one stops you using the 17 at a smaller diagonal, with a smaller resolution but yet 'native' pixels. You get 13... with 1024x768. Thus you can use a lens with more modest FOV.
BTW, with 137mm focal your copy lens is very unlikely to cover even that. Surplusshed had some nice 290mm Fujinons, but they ran out.
Dave, could you comment on the 18'' lenses. I know yours works reasonably, but what about lenses from older series of the same projectors. I am afraid only the newest series give better results in terms of FOV.
Thus not all 18'' FL are guaranteed to give the same results. And there were other brands as well.
BTW, with 137mm focal your copy lens is very unlikely to cover even that. Surplusshed had some nice 290mm Fujinons, but they ran out.
Dave, could you comment on the 18'' lenses. I know yours works reasonably, but what about lenses from older series of the same projectors. I am afraid only the newest series give better results in terms of FOV.
Thus not all 18'' FL are guaranteed to give the same results. And there were other brands as well.
I can't comment on other 18" lenses out there as I haven't tried them. I would assume that if the opaque projector lens has the same physical dimensions and is used for pictures the same size (8" x 10" or bigger) then it will work just about the same; especially if it's from the same company. Granted, there will be slight variations, but I think those differences will be too small to notice.
If you can find an opaque projector lens that supported 14" x 11" papers, then you are GOLDEN for a 17" LCD. I haven't seen one yet, but that doesn't mean they're not there!
If you can find an opaque projector lens that supported 14" x 11" papers, then you are GOLDEN for a 17" LCD. I haven't seen one yet, but that doesn't mean they're not there!
22" opaque projector lenses
I know that some of the 22" lenses are 6" long and some are 7" long. The shorter the better, since a longer one would have a smaller FOV. I have a Beseler 22" that is 6" long, and I think it would work pretty well with a 17" LCD.
Just as an extreme example, I have a 600 mm fl process lens that is only about 3 inches long. It covers at least 20" diagonal perfectly. (Only problem is that it is not very wide, so it is very difficult to get much light through it unless you are willing to use an expensive short-arc lamp.)
I know that some of the 22" lenses are 6" long and some are 7" long. The shorter the better, since a longer one would have a smaller FOV. I have a Beseler 22" that is 6" long, and I think it would work pretty well with a 17" LCD.
Just as an extreme example, I have a 600 mm fl process lens that is only about 3 inches long. It covers at least 20" diagonal perfectly. (Only problem is that it is not very wide, so it is very difficult to get much light through it unless you are willing to use an expensive short-arc lamp.)
when you say not very wide you mean its angle of view?
What is it? I have a 45 degree angle of view process lens i want to buy its 450mm FL and 67mm diameter. Will it work?
Can you explain the light problem?
What is it? I have a 45 degree angle of view process lens i want to buy its 450mm FL and 67mm diameter. Will it work?
Can you explain the light problem?
wide lenses
No, I mean the actual diameter of the lens. Or more important, what is called "the clear aperature". This is really a term from using lenses in photography, where you can make up for a narrow lens aperature by increasing the exposure time.
If you use a process lens, then you will have no problem using even a 19" LCD. They have super-wide Field Of View and excellent flat-field correction. You will get a very sharp image from corner to corner.
But we use fresnel lenses to direct most of the light into the projection lens. You need a design that passes most of that light through the lens. Assuming you have a nice clear LCD (ie. Briteview or with the AntiGlare layer removed) then the fresnels will focus an image of the lamp arc out after the LCD. If you pick the right fresnels and get the distances all adjusted correctly, then the arc image ends up focussed right in the center of the projection lens. That gets the most light through the lens to the screen.
But you also have to pay attention to the size of the arc image and the diameter of the lens. The fresnels work as a second projector and all the usual object/image math applies. If the distance from the arc to the fresnels is 220 mm and the distance from the fresnels to the arc image is 550 mm, then the arc image will be 550/220 = 2.5 times as large as the arc itself. If your arc is 25 mm long, then the arc image would be 62.5 mm long. If you used a 40 mm wide projection lens with that design, you would cut off quite a bit of the light.
To get the most light through your 67 mm diameter process lens you will need to make sure your LCD is clear, your arc length is short enough, and also adjust the fresnel and lamp positions very carefully. Getting it right can make a big difference.
If your LCD is not clear, then you will get a great big blob of light at the projection lens. The larger diameter the lens has, the more light will get to the screen. This is the reason that overhead projector lenses (used with clear transparencies) are small, but opaque projector lenses (used with light randomly reflected off a paper) are very wide.
No, I mean the actual diameter of the lens. Or more important, what is called "the clear aperature". This is really a term from using lenses in photography, where you can make up for a narrow lens aperature by increasing the exposure time.
If you use a process lens, then you will have no problem using even a 19" LCD. They have super-wide Field Of View and excellent flat-field correction. You will get a very sharp image from corner to corner.
But we use fresnel lenses to direct most of the light into the projection lens. You need a design that passes most of that light through the lens. Assuming you have a nice clear LCD (ie. Briteview or with the AntiGlare layer removed) then the fresnels will focus an image of the lamp arc out after the LCD. If you pick the right fresnels and get the distances all adjusted correctly, then the arc image ends up focussed right in the center of the projection lens. That gets the most light through the lens to the screen.
But you also have to pay attention to the size of the arc image and the diameter of the lens. The fresnels work as a second projector and all the usual object/image math applies. If the distance from the arc to the fresnels is 220 mm and the distance from the fresnels to the arc image is 550 mm, then the arc image will be 550/220 = 2.5 times as large as the arc itself. If your arc is 25 mm long, then the arc image would be 62.5 mm long. If you used a 40 mm wide projection lens with that design, you would cut off quite a bit of the light.
To get the most light through your 67 mm diameter process lens you will need to make sure your LCD is clear, your arc length is short enough, and also adjust the fresnel and lamp positions very carefully. Getting it right can make a big difference.
If your LCD is not clear, then you will get a great big blob of light at the projection lens. The larger diameter the lens has, the more light will get to the screen. This is the reason that overhead projector lenses (used with clear transparencies) are small, but opaque projector lenses (used with light randomly reflected off a paper) are very wide.
ok. i measured the arc length of my envelope lamp. it looks like its 35mm. Now the process lens is 480mm FL so using the 550mm FL fresnel in a unsplit design would magnifiy the arc size to 87.5mm
So that would be no good.
So what if i used a 350mm process lens and 220/330 fresnel unsplit? This would give a 51mm arc image which would work at the cost of a shorter throw.
Are you saying that all process lenses can cover a 17 inch lcd or 11 x 14 inch image area? How can I be sure the lens I buy will do the job in terms of FOV? I noticed most process lenses all have 45 degrees angle of view.
So that would be no good.
So what if i used a 350mm process lens and 220/330 fresnel unsplit? This would give a 51mm arc image which would work at the cost of a shorter throw.
Are you saying that all process lenses can cover a 17 inch lcd or 11 x 14 inch image area? How can I be sure the lens I buy will do the job in terms of FOV? I noticed most process lenses all have 45 degrees angle of view.
process lenses
I think that all process lenses are designed to have excellant FOV. So pretty much any process lens with a focal length of 300 mm or higher will cover a 17" LCD. But you are correct: With a long throw lens, you will have to use a very short arc lamp, or use a wider lens. (Like an opaque projector lens.)
If you want to make a good projector with the 450 mm fl process lens, then you would need to use a much shorter lamp arc.
Or the other option is to make a shorter throw projector so the arc image is not too big for a 300-350 mm fl lens with a smaller diameter.
I think that all process lenses are designed to have excellant FOV. So pretty much any process lens with a focal length of 300 mm or higher will cover a 17" LCD. But you are correct: With a long throw lens, you will have to use a very short arc lamp, or use a wider lens. (Like an opaque projector lens.)
If you want to make a good projector with the 450 mm fl process lens, then you would need to use a much shorter lamp arc.
Or the other option is to make a shorter throw projector so the arc image is not too big for a 300-350 mm fl lens with a smaller diameter.
Ok i need to make a decision here. The process lens is actually 20 inch FL and has 2.75 inch clear diameter at the back. thats 69mm
so using a 550/220 fresnel = 2.5. So acording to my calculations the arc size must be no larger then 27mm in order for me to use this lens.
So what 400watt MH lamps have 27mm arc size?
Also can i assume this process lens will be much sharper, better colors, then the LL pro lens or anything in the diy community?
so using a 550/220 fresnel = 2.5. So acording to my calculations the arc size must be no larger then 27mm in order for me to use this lens.
So what 400watt MH lamps have 27mm arc size?
Also can i assume this process lens will be much sharper, better colors, then the LL pro lens or anything in the diy community?
arc length
The Ushio retrofit 400 Watt lamp UHI-S400DD has a 27 mm arc length. I think there are some double-ended MH lamps that have arc lengths even a bit shorter. Look at the lamps at exclusiv-online.com to see how long they are.
A process lens will give you a very sharp, perfectly color-corrected image with a very wide FOV. I have not compared my process lens to any of the recently designed DIY projector lenses. They may give you just as sharp an image. Beyond a certain quality, you have to get up to a couple of feet from the screen to see if the screendoor is gray or black. With the process lens, it will be black because of the low aberration and distortion. But the difference has no effect when you are watching a DVD. Maybe when you try to run windows on screen, you could see a difference.
I would not pay more for a process lens than a $200 DIY lens. You may be able to buy a process lens for less, since a lot of them are being auctioned on eBay. The photo-process lithography they were used for is now mostly obsolete. Digital techniques are replacing photographic. But I still see the lens I bought for $280 selling for $1400 on eBay!
The Ushio retrofit 400 Watt lamp UHI-S400DD has a 27 mm arc length. I think there are some double-ended MH lamps that have arc lengths even a bit shorter. Look at the lamps at exclusiv-online.com to see how long they are.
A process lens will give you a very sharp, perfectly color-corrected image with a very wide FOV. I have not compared my process lens to any of the recently designed DIY projector lenses. They may give you just as sharp an image. Beyond a certain quality, you have to get up to a couple of feet from the screen to see if the screendoor is gray or black. With the process lens, it will be black because of the low aberration and distortion. But the difference has no effect when you are watching a DVD. Maybe when you try to run windows on screen, you could see a difference.
I would not pay more for a process lens than a $200 DIY lens. You may be able to buy a process lens for less, since a lot of them are being auctioned on eBay. The photo-process lithography they were used for is now mostly obsolete. Digital techniques are replacing photographic. But I still see the lens I bought for $280 selling for $1400 on eBay!
ok. this is what i bought. Will it work with a 17 inch lcd perfectly? Did I get a good deal? 6 elements baby!!!! Thats got to be sharper then a pro triplet from LL. Clear back diameter i was told is 2.4 inches.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7609665834&rd=1&sspagename=STRK:MEWA:IT&rd=1
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7609665834&rd=1&sspagename=STRK:MEWA:IT&rd=1
Guy Grotke, you dissapeared. So have a look at that link or someone and give me your opionions please.
uh thats kinda a small diameter to have the right focal length for 17" lcd your focal length is 360 mm = about 14inchs actually
(360 millimeters = 14.1732283 inches) so a lcd under that would be ok but most peaple with 17"lcd use the pro lens or a opaqe lens and it is 6" or 7" inches
in diameter with a focal length of over 500mm or around 19.7 inches roughly so yea my prof opinion is that lens wont work for a 17"lcd.
some one correct me if im wrong here witch i prolly am since i decided to open my mouth
i also have a ushio 400watt for sale fired up 2 times for under a hour total ... prolly more like 10 mins each but yea if your interested make me a offer i also have a socket for it.
(360 millimeters = 14.1732283 inches) so a lcd under that would be ok but most peaple with 17"lcd use the pro lens or a opaqe lens and it is 6" or 7" inches
in diameter with a focal length of over 500mm or around 19.7 inches roughly so yea my prof opinion is that lens wont work for a 17"lcd.
some one correct me if im wrong here witch i prolly am since i decided to open my mouth
i also have a ushio 400watt for sale fired up 2 times for under a hour total ... prolly more like 10 mins each but yea if your interested make me a offer i also have a socket for it.
The diameter is fine I already have that part covered. To calculate de required diameter of your projection lens you do the following:
330/220 (FL of fresnels) = 1.5 x 35mm (arc size)= 52.5mm
The clear back glass diameter of this lens is 60.9mm so i am fine.
330/220 (FL of fresnels) = 1.5 x 35mm (arc size)= 52.5mm
The clear back glass diameter of this lens is 60.9mm so i am fine.
ok i dont get it i guess cuz everyone iv seen trying to use a 17" or 19 " lcd has used the opaq lens thats 6inches or more in diameter .... just to get the all of the lcd yers is only 2.4" how is it going to get the all of the 17"lcd? let alone be able to have the cornders and center in focus.? i dunno maybe im just cunfused...or crazy
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