I know this info is in the forums somewhere, but "Search" isn't pulling much of it out, so I came here.

The problem is this-
I bought a lens on eBay from a seller who didn't know anything about it. It has "Edmund Scientific TV Projection Lens 16,010" written on it, but they don't list it now or have any info on it that I can find. It is 5" in diameter and 5" long, a triplet, and I've measured the focal point to be 11" from one end and 11.5" from the other. What I'm wondering is:
1. Is the focal length measured from the center of the lens or one end?
2. Is one end "special" in that one should face the LCD and one the screen? Both end lenses are curved but one end of the barrel is threaded.
3. What is the best way to determine the field of view?

Thanks!

1) the middle
2) the ring should be the rear
3) try the FOV test for a basic test
The only problem with the test is the image is small so it's kinda hard to tell if it is perfect but it works good and fast.
http://www.lumenlab.com/forums/index.php?showtopic=8190&hl=

That could be a great 16" fl lens good luck

Dave

To find the actual FL of this lens use the Focal Calculatorand some real measurements. You will need to set it up so that you can project some sort of image. Adjust the triplet so that you have a focused image and take measurements of the object and the screen size. Then select the triplet FL check box so that it turns green and enter the measured values in the appropriate boxes. The resulting screen distance and LCD distance will give you the physical FL position on the triplet case.

DJ

I'll throw something together for the tests. I have a Time Bandits poster that should work well. Trying to support the lens will be interesting because it's about 6-7 lbs. Anyway, thanks again.

Making a big leap the model # is 16,010 Maybe 16" fl 10deg feild angle?

That would be a sensible way for them to label a lens, but I think the FL is ~14", max. One side focused 11" from the end of the barrel, one focused 11.5" away, and the barrel is 5" long. So if the focus is inside the triplet somewhere (say 2.5"), 2.5"+11.5" is only 14".

I attempted the FOV test but I don't have appropriate lights and my movie posters are too shiny. I do have an overhead and a mostly working 15" PJ I can mess with if I just get some overhead transparencies. Maybe I'll run down to Office Depot...

Office Depot had ink jet printable transparencies but they were like$30.00 they have something sprayed on one side to make the ink stick. They work well. The nice thing about doing it this way is it will give you all the dimensions of the final PJ. And it will enlarge the image this will make it easier to check how good the lens is.
You will still have to mount the lens in a something. I used a cardboard box draw a circle on it the size of the lens and then draw a smaller circle inside the first one and cut a bunch of small flaps and bend them out and use a couple of raps of tape. If you place the lens mostly inside the box it will stand up well and allow for easy placement.
Any lamp will work for testing a 60 watt bulb won't burn you or melt everything.

Good luck Dave

Ok, I went and got some overhead sheets. No, not the ink jet kind, I couldn't stand paying thirty dollars when all I needed was one sheet. The printout wasn't perfect (but it was good enough); maybe if I turned down the ink volume... Anyway, the best focus seemed to be around 16", so maybe the model number does mean something. I was also able to move the lens pretty well in the focal plane. The focus was good even after it lost brightness from the arc spilling over the edge, which is all I could ask for.

Now I'm wondering what happens to the arc after it enters the first lens in the triplet. If it is smaller in the middle lens I don't need to worry about losing light there, but if it is magnified I might not be able to shift the lens as much as I think. Anyone know?

What size did you make the transparencies? What size PL are you trying to make? It looks like that lens is just a little longer than the stock triplet 330mm v 400mm. It should give a good long throw on a 15" LCD.
The 5" diameter lens could let you use a larger lamp? You could make the brightest DIY PJ ever. Just a thought.

Is the 16” the measurement from the lens to the transparency or is it calculated? Because if it is the transparency to triplet distance then the FL is somewhat smaller than 16”.

DJ

arizonavideo the transparency was about 10"x 7.5". I'm trying to make a PJ with an 8" Hami panel, and if possible to do some lens shifting for a ceiling mount. The major obstacle to the shifting I see now is the size of the arc image. I'm already using fairly large lamp, the Ushio 400W. Also, its arc is going to be magnified by 2.66x at least, because I'm using a 330mm / 124mm fresnel combo. Since the lens is going to be further out than 330mm, the arc will be larger still. I may not end up with much lens movement at all. I figure it will be about as bright as a standard 15". I might be able to eek a little more brightness out by giving up lens shifting and adding a precondenser, but I don't know of any economical tempered ones with appropriate FLs.

DAZZZLA 16" is the measured distance from back of the lens to transparency. Well, roughly - I had a few things in the air even before I picked up the tape measure. I tried to use your program to find the actual FL, but it wouldn't let me change the "LCD Distance". Admittedly I could have tried harder

To BM: I know that everyone says to use a 330mm and a 220mm fresnel but I still think that for a 8" panel you should use two 220mm fresnels. Heres why
A 220mm fresnel is good for a 15 panel but the fresnel is much larger than it will be if you cut it to fit a 7" LCD therefore on a 15" LCD the fresnel gathers more light. The make up for this you should use a shorter rear Fresnel or a condenser lens. Fresnels shorter than 220mm are hard to find. So the easy way is to use two Fresnels of 220mm which now the front 220 is to short to make it focus just move the lamp closer and watch the lamp image re focus at 330mm. This works I tried it all ready. So you will end up with the lamp about 90 to 100mm from the panel. This will be twice as bright!
The arc image should be about the same size.

arizonavideo As I mentioned, I'm planning to use a 330mm front and 124mm rear fresnel combo. The 124 comes from combining a 200mm and 330mm condenser. Since this is almost half the distance and an almost quarter sized panel, I figure it would be similar in brightness to the standard 15" setup. You're saying to use a 220mm front and a 220mm rear? If I only needed two fresnels instead of three that would be better for me, but surely there are drawbacks to this too? I'm not even sure how that works - does the arc image move the exact same amount forward as the light? It seems to me that some of the light that hits the fresnel would be at too steep an angle to be refracted to the LCD, and that since the light won't be going through the LCD perpendicularly anymore that would also introduce some loss. Can you show how it works, with math or some sort of ray drawing? And how do you figure the arc image size in this situation? I'll have to buy another 220 if you're right, so I want to be sure you're right!

Your right about the angle through the LCD but remembers your starting from 0deg so at most you have 10deg or so. The testing I did was with a 330 and a 550mm Fresnel to try see if I could make it reach to 850mm for a 32" fl triplet. It worked but by the time the arc came into focus the rear lamp was way to close about 60mm. Not good for a 17" LCD when I get a 650mm Fresnel I will try again. I wish I could have gotten the 450mm from the group by for testing.
I did not use a LCD just a transparency so I don't know for sure what if any the angle through the LCD will do.
You can do the same test now set up any lamp and your Fresnels use cardboard to see the lamp image [where the triplet should be] move the lamp back or forward the other side does the same. You cold reverse them to see how the arangment works.

Yeah, I suppose I can test how the focus works and check the magnifaction, but I can't determine anything about light loss because I don't have a luxmeter. That's why I wanted to know if you could show why this works (and works better) in theory - otherwise I may never know the difference (but it will still bug me!).

You may lose some because this is not the best angle for the Fresnel. You know that you will lose 9 or 10% with a three Fresnel setup but on the up side two collector Fresnels will block more heat. I can't do lux reading now but soon I will have two meters for testing. One will be for the LL people to use for testing. {Until some one keeps it}
So yes you will be risking $20 for a fresnel.

I'll try to see how this works with two 330mm lenses standing in for the 220s. It's going to be hectic for the next few weeks though.

BTW, if this works the way I think you're saying it does, why didn't you use a 550 field and 550 condenser fresnel combo for your 32" triplet? If you can take distance from the back and move it to the front, don't you want to start with as much in back as possible in your case?

A member has the 32" triplet and a 800mm fresnel was about $165 so it was time to try a "fix" I only have a 220 300 330 550 and a -300mm fresnels to play with a 650 is on its way. They work great moving the lamp a little what the max is will have to be played with some more.
I really don’t like the 550mm so much because it has .3mm grove spacing and that will kill an extra 8 or 10% of the light.
The arc image gets big real fast when you push the lamp closer but it does the same thing with a shorter fresnel so we'll will have to see. When the 650mm Fresnel gets here I’ll do more testing