To all those reading this thread for the first time, welcome to the exciting world of DIY Video Projection from all here at Lumenlab.
This is the Beginner's forum where we aim to answer your initial questions regarding getting you started in DIY projection.
Firstly, we suggest that you have a quick browse of all of the available forums. You'll see that there's quite a few forums aimed at specifc aspects of DIY Projection equipment, as well as DIY Home Theater in general.
When it comes to getting a great result from your first projector, the help you can receive from experienced members can make life a lot easier. You will be a lot more likely to receive a fast, concise answer if your question doesn't leave us having to ask questions about your question.
Finally, we are all here on a voluntary basis, please be patient when waiting for an answer. We're spread all around the world in vastly different timezones so we're not all here all of the time.
Here's a few very important links to read before you dive in:
Visit here for the document outlining the basic operating principles of the DIY projector.
Visit here for a vast array of Projector Terms, Definitions and Abbreviations.
Visit here for a brief safety 'heads up' and answers to a lot of common beginner's questions.
In the following posts I'm going to give some guidelines on how to structure questions and what information we'll need to help you out as quickly as possible.
OK, Let's get some sort of index happening:
FAQ Links:
'Will this projection lens work?'
'Will this *INSERT LIGHT TYPE HERE* be suitable?'
'Will This Particular Metal Halide Lamp be Suitable?'
How To Links:
How to use use the Focal Length Calculator
'How to match Fresnel Focal Lengths to Projection Lenses'
'How to spec Coil/Core Ballast Metal Halide Control Gear'
Full Version: Help Me Help You
We see a lot of 'Will this projection lens work?' questions.
The world of DIY projection is a relatively small part of the projection industry and as such, there are a very limited amount of lenses that will work in our PJs. Our image source is huge compared with commercial DLP or LCD projectors. Lenses designed for use in commercial projectors only have to be big enough to 'see' an image a couple of inches (at the most) diagonal. The focal lengths are also way too short as the image source sits very close to the lens. This renders all such lenses useless for our PJs.
"TV Projection Lenses" can only be used with LCDs with the same or smaller diagonal measurement as the diameter of the lens because the LCD(CRT) rests against the rear of the lens. That's how they are designed to work and is the only way they will work.
Having said that, there are a few lenses that were not specifically designed for DIY PJs that we can use. Some lenses from opaque projectors and some older copiers can be adapted to suit.
To enable us to advise wether or not a particular lens will be suitable please let us know the following if possible:
1. The Lens focal length.
2. The Lens diameter.
3. The size of the LCD panel you intend to use.
4. Any fresnel lens sizes you may be wanting to use.
To work things out by yourself, you can download and play around with the Focal Length Calculator. See this thread for tips on how to use it. It may be a juggling match to get the dimensions to suit your available viewing area, but it is accurate. The LCD and Screen varaibles are their diagonal measurements.
So here's the good oil on Projection Lenses:
For any projection lens to be suitable, when placed at it's focal length away from your image source (LCD), you must be able to see the entire LCD through the lens. A rough way to check this is to set up the lens at it's focal distance away from a sheet of paper and shine a laser through it from various angles. Keep marking dots on the paper until you have determined the extents of the lens's field of view. Remember that the quality of the projection will drop off towards the edges, and that your source is rectangular.
LCD size/Lens Combinations that we know definitely work very well:
Standard Triplet Lens with up to a 15" LCD
Pro Triplet Lens with an LCD between 15" and 19" Widescreen.
Combinations that we know definitely work, but are really stretching the limits:
Standard Triplet Lens with a 17" LCD. I know this works because I'm watching one right now! Quality is only slightly compromised, but it fits so I used it. By the way, quality for TV/DVD is more than adequate, it just gets a bit out of focus on the edges if you are using it as a PC monitor.
Lenses that we know definitely don't work unless you have an LCD the size of a matchbox:
Camera Lenses
Camera Zoom Lenses
Commercial Projector Lenses
(Note: The Help Me Help You topic was created on Jan 20 2007. Please contribute tips/suggestions/corrections and I will edit them into the story...)
The world of DIY projection is a relatively small part of the projection industry and as such, there are a very limited amount of lenses that will work in our PJs. Our image source is huge compared with commercial DLP or LCD projectors. Lenses designed for use in commercial projectors only have to be big enough to 'see' an image a couple of inches (at the most) diagonal. The focal lengths are also way too short as the image source sits very close to the lens. This renders all such lenses useless for our PJs.
"TV Projection Lenses" can only be used with LCDs with the same or smaller diagonal measurement as the diameter of the lens because the LCD(CRT) rests against the rear of the lens. That's how they are designed to work and is the only way they will work.
Having said that, there are a few lenses that were not specifically designed for DIY PJs that we can use. Some lenses from opaque projectors and some older copiers can be adapted to suit.
To enable us to advise wether or not a particular lens will be suitable please let us know the following if possible:
1. The Lens focal length.
2. The Lens diameter.
3. The size of the LCD panel you intend to use.
4. Any fresnel lens sizes you may be wanting to use.
To work things out by yourself, you can download and play around with the Focal Length Calculator. See this thread for tips on how to use it. It may be a juggling match to get the dimensions to suit your available viewing area, but it is accurate. The LCD and Screen varaibles are their diagonal measurements.
So here's the good oil on Projection Lenses:
For any projection lens to be suitable, when placed at it's focal length away from your image source (LCD), you must be able to see the entire LCD through the lens. A rough way to check this is to set up the lens at it's focal distance away from a sheet of paper and shine a laser through it from various angles. Keep marking dots on the paper until you have determined the extents of the lens's field of view. Remember that the quality of the projection will drop off towards the edges, and that your source is rectangular.
LCD size/Lens Combinations that we know definitely work very well:
Standard Triplet Lens with up to a 15" LCD
Pro Triplet Lens with an LCD between 15" and 19" Widescreen.
Combinations that we know definitely work, but are really stretching the limits:
Standard Triplet Lens with a 17" LCD. I know this works because I'm watching one right now! Quality is only slightly compromised, but it fits so I used it. By the way, quality for TV/DVD is more than adequate, it just gets a bit out of focus on the edges if you are using it as a PC monitor.
Lenses that we know definitely don't work unless you have an LCD the size of a matchbox:
Camera Lenses
Camera Zoom Lenses
Commercial Projector Lenses
(Note: The Help Me Help You topic was created on Jan 20 2007. Please contribute tips/suggestions/corrections and I will edit them into the story...)
When it comes to lighting there are a lot of:
'Will this Fluorescent light be suitable?'
'Will this Halogen light be suitable?'
'Will this car headlamp be suitable'
'Will these LEDs be suitable'
...or threads with other titles to that effect.
For some background, see page 6 of the guide outlining the light path in the LL DIY projector.
Here's a few things to be aware of:
1. The 2 fresnel design absolutely relies on the light source being as close to an ideal point as possible.
2. Output/Input, ie Lumens per Watt, the hands down winner is the Metal Halide lamp.
3. The light source has to be extremely bright! It is a fact that around about only 5% of the source light actually makes it to the viewing screen!
While we will never say not to try something different, a lot of experience is floating about these forums and I don't think there are any top projectors using anything but Metal Halide lamps - and there's very good reasons for this. (And please feel free to correct me if I'm wrong!)
Halogens, such as worklights/floodlights, put out a huge amount of Infra Red radiation. Heat is a big killer in an enclosed box. Most halogen worklights also have a very long filament making them less than ideal for the fresnel optics.
Fluorescents, tubes or the newer bayonet/screw fittings, are never really bright enough and you'll never get a point source from one. The only real way that they can be approached is to do away with the rear fresnel and try to make a lightbox (Like the LCD's original backlight)
Car Headlamps, the standard ones are not really bright enough and the reflector isn't right. There's been a bit of talk about HID headlamps recently, but they're really just small Metal halide lamps anyway - and very expensive ones at that - and usually only work on 12V.
LEDs - OK, there's been some PJs made with these but not super-successfully. Keep an eye on it as it's emerging technology. The amount of LED's required will still pump out a considerable amount of heat.
Metal Halides, wether it be Quartz or Ceramic technology produce the most lumens per input Watts, are usually cheap and have simple circuits. The newer technology ceramics have small arc gaps which is getting us closer to our ideal point source of light. The quality of light, which of course depends on the model chosen, can be excellent to reproduce accurate colours.
Remember, we're not saying 'don't ever try some other light source', we're just pointing out some information that might save you a lot of time and money!
(Note: The Help Me Help You topic was created on Jan 20 2007. Please contribute tips/suggestions/corrections and I will edit them into the story...)
'Will this Fluorescent light be suitable?'
'Will this Halogen light be suitable?'
'Will this car headlamp be suitable'
'Will these LEDs be suitable'
...or threads with other titles to that effect.
For some background, see page 6 of the guide outlining the light path in the LL DIY projector.
Here's a few things to be aware of:
1. The 2 fresnel design absolutely relies on the light source being as close to an ideal point as possible.
2. Output/Input, ie Lumens per Watt, the hands down winner is the Metal Halide lamp.
3. The light source has to be extremely bright! It is a fact that around about only 5% of the source light actually makes it to the viewing screen!
While we will never say not to try something different, a lot of experience is floating about these forums and I don't think there are any top projectors using anything but Metal Halide lamps - and there's very good reasons for this. (And please feel free to correct me if I'm wrong!)
Halogens, such as worklights/floodlights, put out a huge amount of Infra Red radiation. Heat is a big killer in an enclosed box. Most halogen worklights also have a very long filament making them less than ideal for the fresnel optics.
Fluorescents, tubes or the newer bayonet/screw fittings, are never really bright enough and you'll never get a point source from one. The only real way that they can be approached is to do away with the rear fresnel and try to make a lightbox (Like the LCD's original backlight)
Car Headlamps, the standard ones are not really bright enough and the reflector isn't right. There's been a bit of talk about HID headlamps recently, but they're really just small Metal halide lamps anyway - and very expensive ones at that - and usually only work on 12V.
LEDs - OK, there's been some PJs made with these but not super-successfully. Keep an eye on it as it's emerging technology. The amount of LED's required will still pump out a considerable amount of heat.
Metal Halides, wether it be Quartz or Ceramic technology produce the most lumens per input Watts, are usually cheap and have simple circuits. The newer technology ceramics have small arc gaps which is getting us closer to our ideal point source of light. The quality of light, which of course depends on the model chosen, can be excellent to reproduce accurate colours.
Remember, we're not saying 'don't ever try some other light source', we're just pointing out some information that might save you a lot of time and money!
(Note: The Help Me Help You topic was created on Jan 20 2007. Please contribute tips/suggestions/corrections and I will edit them into the story...)
We'll often advise you to check out the Focal Length Calculator to aid you in your projection system design. Given a few known quantities you can work out the basis for your projector and screen sizing. Here's some basics of the Focal Length Calculator II.
The dimensions of the following components will determine your projector layout:
1. Your LCD Diagonal measurement - You usually know this, but when you're designing around a predetermined projection size, this is one variable you can change to get the desired result.
2. The Projection Lens Focal Length. For the LL lenses you have the Pro lens with 500mm and the Standard Lens with 320mm. If you have some other lens that you think might be suitable, find its focal length and use it in the calculator. Remember that the focal length isn't the only determining factor in a lens's suitability, it also requires a big enough apeture to be able to see the entire LCD when placed at its focal length away from the LCD.
3. Distance to your screen from the projection lens. This is usually predetermined within a limited range.
4. Screen Size. Now be realistic here! A screen that fills the entire wall may be impressive but it might wear a bit thin after a while. It's all personal preference of course, but remember, a smaller picture will be brighter.
5. Fresnel Layout. Split or Unsplit. Unsplit will give a better image quality as the projection lens is focusing directly on the LCD. A Split design allows the front fresnel to be tilted for Keystone correction. This is required any time that you're projecting at an angle to the screen. In split mode, you can also adjust the distance between the fresnels.
6. Fresnel Focal Length. This only effects the split layout. The LL Standard field fresnel lens, to cover up to a 15" LCD, has a focal length of 317mm, the Pro fresnel lens is 650mm and will cover a 17-19" LCD. Now there's a lot of other fresnel lenses available so when you're choosing a potential candidate, firstly make sure it's big enough to cover your LCD + a few centimetres around the edges. As long as the focal length is close to, but not equal to, your projection lens then all should be OK.
How to Use the Calculator
1. Download the Focal Length Calculator to somewhere on your computer. It doesn't need installation, but if you're having any problems getting it to run see this thread.
2. Run the calculator by double clicking on the .exe file. In the top right of the calculator screen you can choose between split and unsplit setup. You can toggle between the 2 modes to compare distances for each style of setup.
3. The calculator will only compute one calculated distance at a time, all of the other variables must be input. Click on the circle beside the dimension that you wish to calculate. If you don't know one of the variables, you'll have to best guess it to get a result.
4. Be prepared to mix and match units! Screen diagonals are typically measured in inches. Fresnels and Projection Lenses can appear as both
Here's an Example:
I have a wall that will only take an 80" diagonal picture and I'm determined to have a high definition projector (an LCD that will show a minimum native resolution of 1200x720 - most commonly a 17") How far away from the screen will the projector need to be and what lenses will I need to use?
1. Run the calculator and select Unsplit mode. Click the circle (radio button) beside the Screen Distance box. Put 80 in the Screen box and 17 in the LCD box.
2. Typically, for the best picture with a 17" panel you'd go for the Pro lens. The standard lens will just do a 17" LCD, but not perfectly so don't discount this option just yet unless absolute perfection is your goal - sometimes you just have to make it fit! So for now, put 500 in the Triplet FL box.
3. OK, having entered all that, take a look at the Screen Distance result and ask yourself - "Can I place my projector's lens 9.36' away from my screen, directly in line with the centre of the screen?". (If your answer is yes, go out, buy the gear and start building!). More often than not you'll have to adjust all the variables to get the desired result.
4. So 9.36' won't work. Remeber I said to not discount the Standard lens yet? Place 320 in the Triplet FL box and you now get a screen distance of 5.99'. "Wow, this is getting closer to what I need, but there's no way I can put a box directly in front of the screen at that distance, it would be blocking my view". Lets refine things a bit further with....
5. ...Keystone. Keystone is what you get when you project at an angle to the screen. If you're placing your projection lens 6' from the screen, then your projector will need to be on the floor or hanging from the roof - either way it will be at an angle to the screen. The resulting projection will be trapeziodal, tilting the front fresnel will bring this back square. Now there's no hard and fast rule when it comes to keystoning, however, it does require a split configuration so change the calculator to Split mode by clicking the button beside 'Split' in the top right corner. You'll see 2 new boxes appear, Fresnel FL and Fresnel Gap. (Although it doesn't come into our calculations, some would consider a maximum 'off-axis' projection angle to be about 10°)
6. Fresnel FL. Looking back, we've determined sofar that we are using a 17" LCD and the Standard Lens so we'll be looking for a fresnel large enough to cover a 17" LCD with a focal length of around about (but not exactly) 320mm. A quick look through the LL DIY Store and we come up blank, there's nothing like that there. There are other sources for fresnels that aren't available from LL, but I will leave that to another post. For now, it suffices to say that there is a 330FL lens available that is big enough to cover a 17" LCD. So we'll put 330 in the Fresnel FL box.
7. Fresnel Gap. To enable us to tilt the front fresnel, we need a gap between it and the LCD. This gap is measured at the midpoint of the fresnel. For argument's sake, we'll put 50 in the Fresnel Gap box for now.
This now gives you a distance of 5.2' from the projection lens to the screen. Congratulations, you've just completed the basic design for My Projector
So that's how it works! Remember that this is a starting point and not the hard and fast dimensions to build your box to. If you're building a straight-shooter with an unsplit, no keystone setup then you can reliably build a box with minimal adjustment room using these dimensions as a basis. If you are trying something 'out of the box' you will absolutely need a LOT of adjustability. In this case i would reccomend a prototype of sorts just to 'prove the concept' before getting too involved in a final product.
(Note: The Help Me Help You topic was created on Jan 21 2007. Please contribute tips/suggestions/corrections and I will edit them into the story...)
The dimensions of the following components will determine your projector layout:
1. Your LCD Diagonal measurement - You usually know this, but when you're designing around a predetermined projection size, this is one variable you can change to get the desired result.
2. The Projection Lens Focal Length. For the LL lenses you have the Pro lens with 500mm and the Standard Lens with 320mm. If you have some other lens that you think might be suitable, find its focal length and use it in the calculator. Remember that the focal length isn't the only determining factor in a lens's suitability, it also requires a big enough apeture to be able to see the entire LCD when placed at its focal length away from the LCD.
3. Distance to your screen from the projection lens. This is usually predetermined within a limited range.
4. Screen Size. Now be realistic here! A screen that fills the entire wall may be impressive but it might wear a bit thin after a while. It's all personal preference of course, but remember, a smaller picture will be brighter.
5. Fresnel Layout. Split or Unsplit. Unsplit will give a better image quality as the projection lens is focusing directly on the LCD. A Split design allows the front fresnel to be tilted for Keystone correction. This is required any time that you're projecting at an angle to the screen. In split mode, you can also adjust the distance between the fresnels.
6. Fresnel Focal Length. This only effects the split layout. The LL Standard field fresnel lens, to cover up to a 15" LCD, has a focal length of 317mm, the Pro fresnel lens is 650mm and will cover a 17-19" LCD. Now there's a lot of other fresnel lenses available so when you're choosing a potential candidate, firstly make sure it's big enough to cover your LCD + a few centimetres around the edges. As long as the focal length is close to, but not equal to, your projection lens then all should be OK.
How to Use the Calculator
1. Download the Focal Length Calculator to somewhere on your computer. It doesn't need installation, but if you're having any problems getting it to run see this thread.
2. Run the calculator by double clicking on the .exe file. In the top right of the calculator screen you can choose between split and unsplit setup. You can toggle between the 2 modes to compare distances for each style of setup.
3. The calculator will only compute one calculated distance at a time, all of the other variables must be input. Click on the circle beside the dimension that you wish to calculate. If you don't know one of the variables, you'll have to best guess it to get a result.
4. Be prepared to mix and match units! Screen diagonals are typically measured in inches. Fresnels and Projection Lenses can appear as both
Here's an Example:
I have a wall that will only take an 80" diagonal picture and I'm determined to have a high definition projector (an LCD that will show a minimum native resolution of 1200x720 - most commonly a 17") How far away from the screen will the projector need to be and what lenses will I need to use?
1. Run the calculator and select Unsplit mode. Click the circle (radio button) beside the Screen Distance box. Put 80 in the Screen box and 17 in the LCD box.
2. Typically, for the best picture with a 17" panel you'd go for the Pro lens. The standard lens will just do a 17" LCD, but not perfectly so don't discount this option just yet unless absolute perfection is your goal - sometimes you just have to make it fit! So for now, put 500 in the Triplet FL box.
3. OK, having entered all that, take a look at the Screen Distance result and ask yourself - "Can I place my projector's lens 9.36' away from my screen, directly in line with the centre of the screen?". (If your answer is yes, go out, buy the gear and start building!). More often than not you'll have to adjust all the variables to get the desired result.
4. So 9.36' won't work. Remeber I said to not discount the Standard lens yet? Place 320 in the Triplet FL box and you now get a screen distance of 5.99'. "Wow, this is getting closer to what I need, but there's no way I can put a box directly in front of the screen at that distance, it would be blocking my view". Lets refine things a bit further with....
5. ...Keystone. Keystone is what you get when you project at an angle to the screen. If you're placing your projection lens 6' from the screen, then your projector will need to be on the floor or hanging from the roof - either way it will be at an angle to the screen. The resulting projection will be trapeziodal, tilting the front fresnel will bring this back square. Now there's no hard and fast rule when it comes to keystoning, however, it does require a split configuration so change the calculator to Split mode by clicking the button beside 'Split' in the top right corner. You'll see 2 new boxes appear, Fresnel FL and Fresnel Gap. (Although it doesn't come into our calculations, some would consider a maximum 'off-axis' projection angle to be about 10°)
6. Fresnel FL. Looking back, we've determined sofar that we are using a 17" LCD and the Standard Lens so we'll be looking for a fresnel large enough to cover a 17" LCD with a focal length of around about (but not exactly) 320mm. A quick look through the LL DIY Store and we come up blank, there's nothing like that there. There are other sources for fresnels that aren't available from LL, but I will leave that to another post. For now, it suffices to say that there is a 330FL lens available that is big enough to cover a 17" LCD. So we'll put 330 in the Fresnel FL box.
7. Fresnel Gap. To enable us to tilt the front fresnel, we need a gap between it and the LCD. This gap is measured at the midpoint of the fresnel. For argument's sake, we'll put 50 in the Fresnel Gap box for now.
This now gives you a distance of 5.2' from the projection lens to the screen. Congratulations, you've just completed the basic design for My Projector
So that's how it works! Remember that this is a starting point and not the hard and fast dimensions to build your box to. If you're building a straight-shooter with an unsplit, no keystone setup then you can reliably build a box with minimal adjustment room using these dimensions as a basis. If you are trying something 'out of the box' you will absolutely need a LOT of adjustability. In this case i would reccomend a prototype of sorts just to 'prove the concept' before getting too involved in a final product.
(Note: The Help Me Help You topic was created on Jan 21 2007. Please contribute tips/suggestions/corrections and I will edit them into the story...)
We see a lot of questions where people are confused about 'How to match Fresnel Focal Lengths to Projection Lenses'.
So here's the good oil: (Note: We won't mention here the rear (collimating) fresnel, it plays no part in this part of the image projection.) Generally, if you can find a fresnel with a focal length similar to your projection lens then it's worth a shot.
Combinations that we know definitely work very well:
Standard Triplet Lens - 320mm Focal Length with a 317mm or 330mm Fresnel Lens
Pro Triplet Lens - 500mm Focal Length with a 650mm Fresnel Lens
Combinations that we know definitely work:
OK, here's where I need some help. I know there are other combinations that work, Beseler lenses spring to mind. Please be specific with your suggestions!
Combinations that we know definitely don't work:
Pro Triplet Lens - 500mm Focal Length with a 317mm or 330mm (Standard) Fesnel Lens
Standard Triplet Lens - 320mm Focal Length with a 650mm (Pro) Fresnel Lens
(Note: The Help Me Help You topic was created on Jan 24 2007. Please contribute tips/suggestions/corrections and I will edit them into the story...)
So here's the good oil: (Note: We won't mention here the rear (collimating) fresnel, it plays no part in this part of the image projection.) Generally, if you can find a fresnel with a focal length similar to your projection lens then it's worth a shot.
Combinations that we know definitely work very well:
Standard Triplet Lens - 320mm Focal Length with a 317mm or 330mm Fresnel Lens
Pro Triplet Lens - 500mm Focal Length with a 650mm Fresnel Lens
Combinations that we know definitely work:
OK, here's where I need some help. I know there are other combinations that work, Beseler lenses spring to mind. Please be specific with your suggestions!
Combinations that we know definitely don't work:
Pro Triplet Lens - 500mm Focal Length with a 317mm or 330mm (Standard) Fesnel Lens
Standard Triplet Lens - 320mm Focal Length with a 650mm (Pro) Fresnel Lens
(Note: The Help Me Help You topic was created on Jan 24 2007. Please contribute tips/suggestions/corrections and I will edit them into the story...)
For all those wondering 'Will this "INSERT METAL HALIDE BULB MAKE/MODEL HERE" work'. We see these day in and day out, pretty much because there are a gazillion different types of Metal Halide bulbs available.
There's more than a couple of factors that can determine how you choose a bulb. You will have to find the manufacturer of the bulb and be able to get some technical information from them to be able to decide wether they are good enough. This can be extremely difficult as there are thousands of cheap bulbs available with absolutely no documentation. If you choose one of these - good luck!
Wattage - The most common is 400W, with an increasing usage of 150W, 250W and occasionally some upwards of 400W. Above 400W and you're beginning to make a lot of heat. Not saying it can't be done but keep that in mind.
CRI - Colour Rendering Index. There is ongoing debate as to how critical this is, but a general rule of thumb is that the higher the better. CRI is a measure of how accurately a light reproduces colours. Some manufacturer's use a number eg 85, 90, some will use a 'group' 1a 1b etc. Not saying that anything else won't work, but generally aim for something in the 1a (ideal) or 1b group or from 85-100
From OSRAM:
Spectrums show how a light distributes it's power throught all the different colours that go into making it's 'white' light. You will usually only find a lamp's spectrum if you go digging in the manufacturer's tech data, but without one you're only guessing as to what sort of light output you'll get.
The following pic shows 3 different lamp spectrums superimposed on one another. The yellow line outlines the HQI 400W, the blue line is a ceramic 250W and the black is a 150W ceramic. If you can get a bulb with a spectrum like these then all should be good - well, at least it's a good starting point! The spectrum at the top is that of your LCD's red/green/blue filter (or at least our best assumption). The areas where the graph is high lets a lot of light through. If you can find a bulb with peaks in these areas then all the better.
Quartz or Ceramic? - There are 2 types of Metal Halide that come into contention when chosing them for our PJ's. The difference is in the core's containment material. Ceramics are the newer technology, however, as of writing the only really suitable size is 150W and some 250W (which don't have quite the ideal colour temp). The ceramic core bulbs usually have a smaller arc gap than a quartz which helps us to get closer to our ideal point light source.
Colour Temp This is in degrees kelvin, hence the k suffix commonly used. This is the colour that a theoretical "black body" would emit light if it were heated to the specifiec temperature. For projectors the lighting should be at least 4000k up to 6500k. Generally higher is better. (Note that a "warm" light is actually a lower colour temperature than a "cool" light. Go figure.)
Form Factor - the physical size/shape of the bulb. Different manufacturer's have different physical sizing for their bulbs so it's best to get this information from the spec sheets. Here's some of the general shapes you will encounter, as well as the bases. Note, the size of the bulb will determine which reflector you can use.
So, here's some bulbs that we know work very well:
400Watt Quartz:
LL65k, 6500K, CRI group 1a - Ra 91
Osram HQIBT400WD 32000Lumens, 5200K, CRI group 1a - Ra 90-100
150Watt Ceramic:
Philips CDM-TD 150W/942 Base:RX7s (Double Ended)
So, if after all of that you're still not sure if a bulb is suitable, please try and provide the following so we can investigate further:
Manufacturer & Model (at least), and if possible: Colour Temp, CRI, Base Size, Bulb Size and anything else you might know. If you're intersted in a bulb off ebay or from some other source, please try and find this info to help us get an answer back to you quickly. Very few of us have an excess of spare time to chase links
(Note: The Help Me Help You topic was created on Jan 26 2007. Please contribute tips/suggestions/corrections and I will edit them into the story...)
There's more than a couple of factors that can determine how you choose a bulb. You will have to find the manufacturer of the bulb and be able to get some technical information from them to be able to decide wether they are good enough. This can be extremely difficult as there are thousands of cheap bulbs available with absolutely no documentation. If you choose one of these - good luck!
Wattage - The most common is 400W, with an increasing usage of 150W, 250W and occasionally some upwards of 400W. Above 400W and you're beginning to make a lot of heat. Not saying it can't be done but keep that in mind.
CRI - Colour Rendering Index. There is ongoing debate as to how critical this is, but a general rule of thumb is that the higher the better. CRI is a measure of how accurately a light reproduces colours. Some manufacturer's use a number eg 85, 90, some will use a 'group' 1a 1b etc. Not saying that anything else won't work, but generally aim for something in the 1a (ideal) or 1b group or from 85-100
From OSRAM:
Spectrums show how a light distributes it's power throught all the different colours that go into making it's 'white' light. You will usually only find a lamp's spectrum if you go digging in the manufacturer's tech data, but without one you're only guessing as to what sort of light output you'll get.
The following pic shows 3 different lamp spectrums superimposed on one another. The yellow line outlines the HQI 400W, the blue line is a ceramic 250W and the black is a 150W ceramic. If you can get a bulb with a spectrum like these then all should be good - well, at least it's a good starting point! The spectrum at the top is that of your LCD's red/green/blue filter (or at least our best assumption). The areas where the graph is high lets a lot of light through. If you can find a bulb with peaks in these areas then all the better.
Quartz or Ceramic? - There are 2 types of Metal Halide that come into contention when chosing them for our PJ's. The difference is in the core's containment material. Ceramics are the newer technology, however, as of writing the only really suitable size is 150W and some 250W (which don't have quite the ideal colour temp). The ceramic core bulbs usually have a smaller arc gap than a quartz which helps us to get closer to our ideal point light source.
Colour Temp This is in degrees kelvin, hence the k suffix commonly used. This is the colour that a theoretical "black body" would emit light if it were heated to the specifiec temperature. For projectors the lighting should be at least 4000k up to 6500k. Generally higher is better. (Note that a "warm" light is actually a lower colour temperature than a "cool" light. Go figure.)
Form Factor - the physical size/shape of the bulb. Different manufacturer's have different physical sizing for their bulbs so it's best to get this information from the spec sheets. Here's some of the general shapes you will encounter, as well as the bases. Note, the size of the bulb will determine which reflector you can use.
So, here's some bulbs that we know work very well:
400Watt Quartz:
LL65k, 6500K, CRI group 1a - Ra 91
Osram HQIBT400WD 32000Lumens, 5200K, CRI group 1a - Ra 90-100
150Watt Ceramic:
Philips CDM-TD 150W/942 Base:RX7s (Double Ended)
So, if after all of that you're still not sure if a bulb is suitable, please try and provide the following so we can investigate further:
Manufacturer & Model (at least), and if possible: Colour Temp, CRI, Base Size, Bulb Size and anything else you might know. If you're intersted in a bulb off ebay or from some other source, please try and find this info to help us get an answer back to you quickly. Very few of us have an excess of spare time to chase links
(Note: The Help Me Help You topic was created on Jan 26 2007. Please contribute tips/suggestions/corrections and I will edit them into the story...)
There are essentially 2 different types of control gear for Metal Halide lamps: Electronic or Coil/Core. Electronic 'Ballasts' are an all-in-one solution - Power in one end, bulb on the other. Coil/Core consists of a number of components and occasionally we see questions regarding finding Coil/Core Ballast control gear for Metal Halide Lamps.
A lot of the following text was taken from various Tridonic Atco pdf's. (I have used Atco's gear exclusively in my first PJ for over a year now without any problems whatsoever.)
Operating principles of High Intensity Discharge lamps. .
All Metal Halide lamps require a current limiting device to control lamp current - the ballast. Ballasts work on the self inductance principle. The impedance of the ballast is set to match the arc voltage of the particular lamp, which ensures that the correct current is supplied. In some cases a ballast can be used for more than one type of lamp, but a lamp should never be used with any ballast other than the correct one. Also any supply voltage or frequency variation will affect the optimum performance, so the ballast type with the correct nominal values should be used in these circumstances.
The starting voltage for most High-Intensity Discharge (HID) lamps, especially metal halide and high-pressure sodium types, is higher than the mains voltage. Ignitors provide the necessary high voltage to start such lamps. The high-voltage pulse varies from 1 to 5kV depending upon the type of the lamp and is inhibited when the lamp starts.
HID lamp circuits have an inherently low power factor (around 0.4 to 0.5) due to the control gear inductance which is in the circuit to limit the current through the lamp. Raising the power factor by means of the inclusion of a capacitor (opposite effect to an inductor) substantially reduces the current drawn from the mains.
The components:
Ballasts:
The ballast you choose depends entirely on your bulb's requirements. Your bulb will have a designed operating Voltage and Current which will be listed on it's spec sheet. You will have to find this information to be able to choose the correct ballast. The ballast's spec sheet will have a rated output voltage and current - these must match your bulb's specs. When looking through a manufacturer's ballast spec sheets you will find ballasts for all types of discharge lamps. The ones you need to look for are listed as Metal Halide.
As the newer, short arc 150W ceramic bulbs age, they may become polarised. The polarisation superimposes a d.c. component on the a.c. lamp current. The combination of the a.c. and d.c. components results in a higher than normal current to flow causing overheating of the control equipment. Because of this characteristic, suitable protected circuits will need to be used for the safe operation of these lamps. The most common is a self-resetting thermal cut-out which rests against the ballast winding. This switches the circuit off when the temperature of the ballast increases beyond the maximum permissible winding temperature. Once the device cools down, the lamp will re-ignite and the circuit will continue to cycle. Ballasts with this feature will be marked 'Thermal Cutout' or TH or similar.
Ignitors:
There are two types of ignitors: Superimposed-Pulse Ignitors and Impulser Ignitors.
Superimposed-Pulse Ignitors
Superimposed-Pulse Ignitors produce the high-voltage pulses totally within the ignitor, isolating the ballast from the high voltage. The pulse voltage is present only on the lead from the ignitor to the centre contact of the lamp. This feature ensures a more reliable system particularly at the end of lamp life when the ignitor repeatedly tries to restart the lamp as no damage is done to the insulation of the ballast.
Impulser Ignitors
With Impulser Ignitors the ballast coil acts as a step-up auto transformer or a resonant inductor to produce the required high lamp-starting voltage. In all three circuits the ballast and the lamp are both subjected to their high-voltage pulses. The ignitor switches off once the arc has struck. However, at the end of lamp life the ignitor repeatedly tries to restart the lamp. This action may eventually destroy the ballast coil if the lamp is not changed or the luminaire switched off. This feature demands that the ballast and the ignitor must be carefully matched to ensure long life. Unlike superimposed ignitor systems, impulser ignitors may be mounted long distance – some up to 100m – from the lamp.
Capacitors:
The capacitors are required to bring the power factor of the system back to near 1. I do not know of any way to calculate the capacitor required, however, every ballast spec sheet I have seen has the required capacitor listed.
So, what does that all mean for us?
Compatability: I think it's ideal to get all of the control gear from a single manufacturer. Most manufacturer's will have spec sheets for all of their components and quite often will list the correct combinations. Either way, a quick call to their technical departments should be able to let you know if a certain combination will work. This way you'll get a product that will definitely work.
Voltages. Believe it or not, there are many different voltages and line frequencies in use throughout the world. When you're asking questions about certain components you must state what voltage/frequency you will be using.
Ignitors. I have only seen Superimposed-Pulse Ignitors used in control gear for our lamps. I don't think Impulse Ignitors need be considered, I just mentioned them to let you know that you might see them when searching for ignitors.
How do I hook it all up? All of the components I have seen and worked with have the circuit diagram etched on them! If you really can't work out where it all goes get an Electrician or you could kill yourself! - seriously. There are some very high voltages at play here.
This is from a Tridonic Atco pdf, but most circuits with Superimposed-Pulse Ignitors are similar.
NOTE: THE FOLLOWING TABLES FROM TRIDONIC ATCO ARE FOR 240V SYSTEMS ONLY and lists Atco components for some common lamps. You should be able to obtain datasheets like this from any reputable control gear manufacturer. If you can't get it, then you're probably better off going elsewhere
(Note: The Help Me Help You topic was created on Jan 27 2007. Please contribute tips/suggestions/corrections and I will edit them into the story...)
A lot of the following text was taken from various Tridonic Atco pdf's. (I have used Atco's gear exclusively in my first PJ for over a year now without any problems whatsoever.)
Operating principles of High Intensity Discharge lamps. .
All Metal Halide lamps require a current limiting device to control lamp current - the ballast. Ballasts work on the self inductance principle. The impedance of the ballast is set to match the arc voltage of the particular lamp, which ensures that the correct current is supplied. In some cases a ballast can be used for more than one type of lamp, but a lamp should never be used with any ballast other than the correct one. Also any supply voltage or frequency variation will affect the optimum performance, so the ballast type with the correct nominal values should be used in these circumstances.
The starting voltage for most High-Intensity Discharge (HID) lamps, especially metal halide and high-pressure sodium types, is higher than the mains voltage. Ignitors provide the necessary high voltage to start such lamps. The high-voltage pulse varies from 1 to 5kV depending upon the type of the lamp and is inhibited when the lamp starts.
HID lamp circuits have an inherently low power factor (around 0.4 to 0.5) due to the control gear inductance which is in the circuit to limit the current through the lamp. Raising the power factor by means of the inclusion of a capacitor (opposite effect to an inductor) substantially reduces the current drawn from the mains.
The components:
Ballasts:
The ballast you choose depends entirely on your bulb's requirements. Your bulb will have a designed operating Voltage and Current which will be listed on it's spec sheet. You will have to find this information to be able to choose the correct ballast. The ballast's spec sheet will have a rated output voltage and current - these must match your bulb's specs. When looking through a manufacturer's ballast spec sheets you will find ballasts for all types of discharge lamps. The ones you need to look for are listed as Metal Halide.
As the newer, short arc 150W ceramic bulbs age, they may become polarised. The polarisation superimposes a d.c. component on the a.c. lamp current. The combination of the a.c. and d.c. components results in a higher than normal current to flow causing overheating of the control equipment. Because of this characteristic, suitable protected circuits will need to be used for the safe operation of these lamps. The most common is a self-resetting thermal cut-out which rests against the ballast winding. This switches the circuit off when the temperature of the ballast increases beyond the maximum permissible winding temperature. Once the device cools down, the lamp will re-ignite and the circuit will continue to cycle. Ballasts with this feature will be marked 'Thermal Cutout' or TH or similar.
Ignitors:
There are two types of ignitors: Superimposed-Pulse Ignitors and Impulser Ignitors.
Superimposed-Pulse Ignitors
Superimposed-Pulse Ignitors produce the high-voltage pulses totally within the ignitor, isolating the ballast from the high voltage. The pulse voltage is present only on the lead from the ignitor to the centre contact of the lamp. This feature ensures a more reliable system particularly at the end of lamp life when the ignitor repeatedly tries to restart the lamp as no damage is done to the insulation of the ballast.
Impulser Ignitors
With Impulser Ignitors the ballast coil acts as a step-up auto transformer or a resonant inductor to produce the required high lamp-starting voltage. In all three circuits the ballast and the lamp are both subjected to their high-voltage pulses. The ignitor switches off once the arc has struck. However, at the end of lamp life the ignitor repeatedly tries to restart the lamp. This action may eventually destroy the ballast coil if the lamp is not changed or the luminaire switched off. This feature demands that the ballast and the ignitor must be carefully matched to ensure long life. Unlike superimposed ignitor systems, impulser ignitors may be mounted long distance – some up to 100m – from the lamp.
Capacitors:
The capacitors are required to bring the power factor of the system back to near 1. I do not know of any way to calculate the capacitor required, however, every ballast spec sheet I have seen has the required capacitor listed.
So, what does that all mean for us?
Compatability: I think it's ideal to get all of the control gear from a single manufacturer. Most manufacturer's will have spec sheets for all of their components and quite often will list the correct combinations. Either way, a quick call to their technical departments should be able to let you know if a certain combination will work. This way you'll get a product that will definitely work.
Voltages. Believe it or not, there are many different voltages and line frequencies in use throughout the world. When you're asking questions about certain components you must state what voltage/frequency you will be using.
Ignitors. I have only seen Superimposed-Pulse Ignitors used in control gear for our lamps. I don't think Impulse Ignitors need be considered, I just mentioned them to let you know that you might see them when searching for ignitors.
How do I hook it all up? All of the components I have seen and worked with have the circuit diagram etched on them! If you really can't work out where it all goes get an Electrician or you could kill yourself! - seriously. There are some very high voltages at play here.
This is from a Tridonic Atco pdf, but most circuits with Superimposed-Pulse Ignitors are similar.
NOTE: THE FOLLOWING TABLES FROM TRIDONIC ATCO ARE FOR 240V SYSTEMS ONLY and lists Atco components for some common lamps. You should be able to obtain datasheets like this from any reputable control gear manufacturer. If you can't get it, then you're probably better off going elsewhere
(Note: The Help Me Help You topic was created on Jan 27 2007. Please contribute tips/suggestions/corrections and I will edit them into the story...)
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