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Reflector
I've ordered one of those ellipsoidal reflectors too, but the 'buy it now' price went up to $11. It appears to be exactly the same as the one in the Leko I got yesterday. The relector is just too small to be used with the large 400w MH, so I guess I'll be buying one of the smaller 400w MH bulbs so I can get the light source into the focal point. The smaller ones seem to be identical to the larger ones but with a smaller envelope and correspondingly shorter expected life.
FYI - The Leko is set up with an adjustable holder so the bulb can be moved into optimal position within the reflector. Then the whole bulb housing can be slid within the lens housing to position the bulb and reflector with respect to the output lens. After analyzing it, I've decided to sell it rather than try modifying and using for my projector.
I've ordered one of those ellipsoidal reflectors too, but the 'buy it now' price went up to $11. It appears to be exactly the same as the one in the Leko I got yesterday. The relector is just too small to be used with the large 400w MH, so I guess I'll be buying one of the smaller 400w MH bulbs so I can get the light source into the focal point. The smaller ones seem to be identical to the larger ones but with a smaller envelope and correspondingly shorter expected life.
FYI - The Leko is set up with an adjustable holder so the bulb can be moved into optimal position within the reflector. Then the whole bulb housing can be slid within the lens housing to position the bulb and reflector with respect to the output lens. After analyzing it, I've decided to sell it rather than try modifying and using for my projector.
woneill said:
I received a sheet of this stuff Friday. Its very thick and nearly clear, with little optical distortion. I held it in front of my monitor and noticed only a slight grayish tint. As you might expect, one side is labeled to face toward the bulb.
I haven't tried really using it yet, as I'm still trying to settle on a bulb and reflector combination. Should work great though, as its designed to be used with much hotter lights than I'll be using!
When we talk about point source light, actually we don't need big reflector too, ideal is just slightly bigger than point source light itself.
Together with direct light beam, the reflector will spread another half of the light beam (undirect) and must cover the whole fresnel panel in front of the lamp to produce near perfect parallel light beam, am I right?
Someone said, I forgot the name, that half sphere can be used to produce parallel light beam, with placing the light source at 1/2 of the sphere radius? Is it true? If it works then why we use parabolic reflector? Since half sphere is much easier to make than parabolic to get the same result (parallel light beam).
Together with direct light beam, the reflector will spread another half of the light beam (undirect) and must cover the whole fresnel panel in front of the lamp to produce near perfect parallel light beam, am I right?
Someone said, I forgot the name, that half sphere can be used to produce parallel light beam, with placing the light source at 1/2 of the sphere radius? Is it true? If it works then why we use parabolic reflector? Since half sphere is much easier to make than parabolic to get the same result (parallel light beam).
Hi Gunawan,
With a point source, if you are only going to use a tiny percentage of the light emitted by the bulb, then the reflector doesn't need to be very big. In the classic point source thing, only a small amount of light from the bulb goes in the direction of the screen.
You get higher uniformity that way, but at an overall reduced light level. If you use shorter focal-length fresnels, then you can use a bigger solid angle of the light from the bulb, but then the uniformity suffers big time with the intensity fall-off tending towards 1/r^2 where r is measured from the center of the screen. Also, the fresnels aren't as good at the shorter focal lengths...
As for the parallel beam, if the radius of the sphere is BIG compared to the width of the beam - then yes, the output of a spherical reflector will approximate to a parallel beam. The reason is that the base of a parabola approximates very close to a spherical surface very close to its axis.
The problem with using a spherical reflector is that you get spherical abberation - exactly the same as with a lens. This is why the a lens generally works "ideally" if its radius of curvature is much bigger than its diameter...
Thus, you can use spherical reflectors very nicely in telescopes if the radius of the sphere is MUCH bigger than the radius of the mirror.
Otherwise, we would all be using soccer balls and tinfoil to generate pure parallel reflectors...
Bill.
With a point source, if you are only going to use a tiny percentage of the light emitted by the bulb, then the reflector doesn't need to be very big. In the classic point source thing, only a small amount of light from the bulb goes in the direction of the screen.
You get higher uniformity that way, but at an overall reduced light level. If you use shorter focal-length fresnels, then you can use a bigger solid angle of the light from the bulb, but then the uniformity suffers big time with the intensity fall-off tending towards 1/r^2 where r is measured from the center of the screen. Also, the fresnels aren't as good at the shorter focal lengths...
As for the parallel beam, if the radius of the sphere is BIG compared to the width of the beam - then yes, the output of a spherical reflector will approximate to a parallel beam. The reason is that the base of a parabola approximates very close to a spherical surface very close to its axis.
The problem with using a spherical reflector is that you get spherical abberation - exactly the same as with a lens. This is why the a lens generally works "ideally" if its radius of curvature is much bigger than its diameter...
Thus, you can use spherical reflectors very nicely in telescopes if the radius of the sphere is MUCH bigger than the radius of the mirror.
Otherwise, we would all be using soccer balls and tinfoil to generate pure parallel reflectors...
Bill.
Hey Bill....
What's the word on that reflector from eBay? I'm still trying to find a reflector solution, and my local lighting store is dragging its feet trying to get me a Markar-type downlight reflector. If the eBay one's big enough for the 400W MH, I'll try that.
What's the word on that reflector from eBay? I'm still trying to find a reflector solution, and my local lighting store is dragging its feet trying to get me a Markar-type downlight reflector. If the eBay one's big enough for the 400W MH, I'll try that.
Still waiting...
I'm working offsite, and it is supposed to be delivered to the office. I'll maybe get it on Friday.
I'm working offsite, and it is supposed to be delivered to the office. I'll maybe get it on Friday.
Re: Hey Bill....
Like Bill, I bought a couple of those to play with too. Based on dimensions given on eBay, they appear to be the same size as the one in the Leko I bought earlier – about 6” at the top with 3/4” opening. I tried a ‘dry-fit’ of the top of my larger 400 MH bulb into that reflector and found that I couldn’t get the light source in deep enough to reach the focal point. The reflector fit almost like a cap on the top of the bulb, directly in contact with the glass. I immediately remembered undream’s experience with the aluminum foil and the fried bulb!
I’m hoping it’ll work out with a smaller MH bulb. I bought one of the smaller envelope Phillips 400w MH’s from Home Depot, and when I receive the reflectors from KayeLights (eBay seller - http://www.kayelights.com/) intend to try modifying the bulb opening to allow the base to fit through. If I can get part of the light source into the focal point with some (at least 1/4”?) of air space between the glass and reflector, I’d be willing to try it with some forced-air cooling.
HokieTT said:
Like Bill, I bought a couple of those to play with too. Based on dimensions given on eBay, they appear to be the same size as the one in the Leko I bought earlier – about 6” at the top with 3/4” opening. I tried a ‘dry-fit’ of the top of my larger 400 MH bulb into that reflector and found that I couldn’t get the light source in deep enough to reach the focal point. The reflector fit almost like a cap on the top of the bulb, directly in contact with the glass. I immediately remembered undream’s experience with the aluminum foil and the fried bulb!
I’m hoping it’ll work out with a smaller MH bulb. I bought one of the smaller envelope Phillips 400w MH’s from Home Depot, and when I receive the reflectors from KayeLights (eBay seller - http://www.kayelights.com/) intend to try modifying the bulb opening to allow the base to fit through. If I can get part of the light source into the focal point with some (at least 1/4”?) of air space between the glass and reflector, I’d be willing to try it with some forced-air cooling.
mycamel....
I'm a tad confused about the bulb sizes. I do remember when I got my bulb at Home Depot, they had 2 sizes...a HUGE one and a smaller, but still very large, one. I bought the smaller one. Now, my question is, which one are you referring to with your tests? Did you find a third, 'baby-sized' buld? Or did you start out with the monster one and are now progressing to the one I had? Mine cost $31, I believe. The huge one was much cheaper...under $20, I think. Thanks.
I'm a tad confused about the bulb sizes. I do remember when I got my bulb at Home Depot, they had 2 sizes...a HUGE one and a smaller, but still very large, one. I bought the smaller one. Now, my question is, which one are you referring to with your tests? Did you find a third, 'baby-sized' buld? Or did you start out with the monster one and are now progressing to the one I had? Mine cost $31, I believe. The huge one was much cheaper...under $20, I think. Thanks.
Re: mycamel....
I wish there was a smaller 400w MH for about the same money. If anyone finds one, be sure to post please!
Yes, I started with the monster and that's the one that will not work with the small reflectors I'm referring to.
HokieTT said:
I wish there was a smaller 400w MH for about the same money. If anyone finds one, be sure to post please!
Yes, I started with the monster and that's the one that will not work with the small reflectors I'm referring to.
Reflector impasse
Okay guys, I'm at the end of my rope, reflector-wise.
My projector project (pun alert!) has been at a virtual standstill for 4-5 weeks now. The parabolic reflector I got from Edmund Optics just didn't cut it. I've had my heart set on trying an Ellipsoidal reflector (Marklar-type), but I just got screwed over by my local lighting company. They made me wait almost 3 weeks to finally tell me they hadn't done any looking into my situation and frankly didn't have any desire to. This after I printed out and brought in spec sheets and photos of the reflector, and talked for a while with the salesman about what I was looking for and the substitutes I would accept.
So basically, if no one can find a suitable reflector available for purchase online, I'm going to have to give up this project. I can't proceed any further without a reflector. I can't believe no one has found anything suitable yet.
Any help?
Okay guys, I'm at the end of my rope, reflector-wise.
My projector project (pun alert!) has been at a virtual standstill for 4-5 weeks now. The parabolic reflector I got from Edmund Optics just didn't cut it. I've had my heart set on trying an Ellipsoidal reflector (Marklar-type), but I just got screwed over by my local lighting company. They made me wait almost 3 weeks to finally tell me they hadn't done any looking into my situation and frankly didn't have any desire to. This after I printed out and brought in spec sheets and photos of the reflector, and talked for a while with the salesman about what I was looking for and the substitutes I would accept.
So basically, if no one can find a suitable reflector available for purchase online, I'm going to have to give up this project. I can't proceed any further without a reflector. I can't believe no one has found anything suitable yet.
Any help?
Hi Guys,
Back from the field... I picked up my reflector this morning, and as expected, it is too small for one of the 400W monster MH bulbs.
Its focal point is too close to its base, and the hole at the back is only 3/4" diameter. 🙁
It is definitely interesting, though. I can't figure out whether it is made of aluminium or aluminised plastic. I think, aluminium.
I will probably use it anyway, because I tend to prefer the smaller HMI/HQI Metal Halide bulb variants, and for these, it is perfect. They cost more than the big ones, but they are much smaller and easier to use efficiently.
Has anybody tried the idea posted earlier about using a cardboard/chipboard elliptical cut-out to "lathe" a wet plaster/clay block into a suitably elliptical dome that could be used as a base to form an elliptical reflector from aluminium foil/sheeting?
I think the idea was ingenious, because once the curves and shape is set (and the plaster/clay dry), it would be easy enough to cut and wrap a suitably sized 1mm thick aluminium sheet into a high quality reflector that would be more than accurate enough for the needs of the project.
Bill.
Back from the field... I picked up my reflector this morning, and as expected, it is too small for one of the 400W monster MH bulbs.
Its focal point is too close to its base, and the hole at the back is only 3/4" diameter. 🙁
It is definitely interesting, though. I can't figure out whether it is made of aluminium or aluminised plastic. I think, aluminium.
I will probably use it anyway, because I tend to prefer the smaller HMI/HQI Metal Halide bulb variants, and for these, it is perfect. They cost more than the big ones, but they are much smaller and easier to use efficiently.
Has anybody tried the idea posted earlier about using a cardboard/chipboard elliptical cut-out to "lathe" a wet plaster/clay block into a suitably elliptical dome that could be used as a base to form an elliptical reflector from aluminium foil/sheeting?
I think the idea was ingenious, because once the curves and shape is set (and the plaster/clay dry), it would be easy enough to cut and wrap a suitably sized 1mm thick aluminium sheet into a high quality reflector that would be more than accurate enough for the needs of the project.
Bill.
Attachments
Spotlight reflector
woneill;
I to purchased one of these reflectors. I agree it is too small for standard MH bulbs. I've been doing research on possible bulb alternatives and have found something that might work. The following links are to a 400W T-15 or T-17 MH bulb. For those who don't the "T" stands for tubular and the number (15 or 17) stands for the diameter of the bulb envelope in 1/8th's of an inch.
http://www.eyelighting.com/mhconversioncleanace.html
http://www.hellolights.com/400wat65iw.html
There are several great things about this bulb compared to standard MH bulbs.
1. Smaller size. It's approximately 2" in dia. and about 9" long.
2. Color temp of 6500k compared to 3000k-4000k.
3. CRI of 90 compared to 65.
4. Will run on a standard M59 MH ballast or a H33 MV ballast.
The manufacture's web site states that it should only be run on the H33 ballast, but every other reference I've seen says that it will run on either ballast. This bulb is quite popular for reef aquarium lighting. A quick Google search for "Iwasaki metal halide" should confirm this if anyones concerned.
The downsides are slightly less luminous output and a rated life of "only" 9000 hrs🙂.
I think this bulb should work with the reflector because the filament in the original bulb is oriented along the projection axis as will be this bulb.
I plan on enlarging the hole in the bottom of the reflector with 2 1/4" hole saw. This will allow adjustment of the bulb within the reflector to obtain an optimum output beam.
I've ordered the bulb and will post back with results as time permits.
Patrick
woneill;
I to purchased one of these reflectors. I agree it is too small for standard MH bulbs. I've been doing research on possible bulb alternatives and have found something that might work. The following links are to a 400W T-15 or T-17 MH bulb. For those who don't the "T" stands for tubular and the number (15 or 17) stands for the diameter of the bulb envelope in 1/8th's of an inch.
http://www.eyelighting.com/mhconversioncleanace.html
http://www.hellolights.com/400wat65iw.html
There are several great things about this bulb compared to standard MH bulbs.
1. Smaller size. It's approximately 2" in dia. and about 9" long.
2. Color temp of 6500k compared to 3000k-4000k.
3. CRI of 90 compared to 65.
4. Will run on a standard M59 MH ballast or a H33 MV ballast.
The manufacture's web site states that it should only be run on the H33 ballast, but every other reference I've seen says that it will run on either ballast. This bulb is quite popular for reef aquarium lighting. A quick Google search for "Iwasaki metal halide" should confirm this if anyones concerned.
The downsides are slightly less luminous output and a rated life of "only" 9000 hrs🙂.
I think this bulb should work with the reflector because the filament in the original bulb is oriented along the projection axis as will be this bulb.
I plan on enlarging the hole in the bottom of the reflector with 2 1/4" hole saw. This will allow adjustment of the bulb within the reflector to obtain an optimum output beam.
I've ordered the bulb and will post back with results as time permits.
Patrick
Hey guys,
Why couldn`t you just build a sqaure rack and put bulbs all the way around the rack and in the middle to have an ( pretty much)evenly distributed light. Then stick it right behind the LCD. Of course you`ll need a lexan lens or something...
I don`t know much about this project yet so this might be a stupid idea...
Mitch
Why couldn`t you just build a sqaure rack and put bulbs all the way around the rack and in the middle to have an ( pretty much)evenly distributed light. Then stick it right behind the LCD. Of course you`ll need a lexan lens or something...
I don`t know much about this project yet so this might be a stupid idea...
Mitch
Mitch,
There is still debate on this topic in the main thread. I personally subscribe to this model being viable using 10/12 MR11 halogens with built-in spot reflectors and narrow beams.
The problem here is that the halogens operate at a lower colour temperature than the pure-white MH bulbs, and generate more heat per lumen.
The good side is that they are easier and cheaper to connect up than the MH bulbs - no ballast required - and allow for a much more compact light unit than the MH monsters. Also, our eyes/brains adjust much more effectively than people seem to think to changes in colour temperature, and the effects would not be very noticeable...
The trick here in these forums is to explore ALL ideas and contribute as a whole to as many different strategies as possible. That way, everybody's understanding increases, and the chances are, we will get more breakthroughs.
Bill.
There is still debate on this topic in the main thread. I personally subscribe to this model being viable using 10/12 MR11 halogens with built-in spot reflectors and narrow beams.
The problem here is that the halogens operate at a lower colour temperature than the pure-white MH bulbs, and generate more heat per lumen.
The good side is that they are easier and cheaper to connect up than the MH bulbs - no ballast required - and allow for a much more compact light unit than the MH monsters. Also, our eyes/brains adjust much more effectively than people seem to think to changes in colour temperature, and the effects would not be very noticeable...
The trick here in these forums is to explore ALL ideas and contribute as a whole to as many different strategies as possible. That way, everybody's understanding increases, and the chances are, we will get more breakthroughs.
Bill.
ok,
So has anybody tried this yet? If I was to build this square frame and put lights all around it, then stick a Lexan lens between the lights and LCD screen to keep the heat away from the LCD, it seems to me that this would give me an evenly distributed light.
I don`t have all my stuff to start this project yet or else I`d be contributing ideas out the wazoo! So please don`t think I`m trying to wiezel out of experimentin`.
Mitch
So has anybody tried this yet? If I was to build this square frame and put lights all around it, then stick a Lexan lens between the lights and LCD screen to keep the heat away from the LCD, it seems to me that this would give me an evenly distributed light.
I don`t have all my stuff to start this project yet or else I`d be contributing ideas out the wazoo! So please don`t think I`m trying to wiezel out of experimentin`.
Mitch
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