Home Made Tank Light - The Swan Blaster 260W Short Arc

[get-lit]

I calculated MCP at various distances with your configuration having 18200 Lamp Lumen (estimated from 70 L/W x 260W), 98% Reflectance AQ Reflector and 90% Transparent Polycarbonate Lens.

200' 44.465 MCP
500' 60.505 MCP
750' 65.83 MCP
1000' 68.87 MCP
2000' 74.02 MCP
3000' 75.915 MCP
4000' 76.9 MCP
5000' 77.505 MCP
10000' 78.745 MCP
100000' 79.895 MCP
1000000' 80.015 MCP
10000000' 80.02 MCP
10000000' 80.025 MCP
100000000' 80.025 MCP

I'm sure there's some info out there somewhere about light absorption/scatter with distance through the atmospheric conditions that would allow you to determine the optimal measurement distance for your light. I'll do some reading. That Polycarbonate is blocking pretty much ALL of the UV light BTW, but the bugs still use the blue light to find food.

EDIT: With thin dry clean air, visible light is not absorbed through the entire thickness of the atmosphere, however light toward the blue end of the spectrum does scatter through the atmosphere, which is why you see a blue beam with a white spot. So the blue light scatter is really the only hindrance. Probably the best bet is to take the measurement as far as you can in clean dry high altitude air, measure the color temp and measure it up close, and then compare the different color temps to calculate the amount of blue light lost at the measured distance so you can add it in.


With all this in mind, it makes me wonder what one is able to claim the actual CP of their light is. Theoretically, your light is 80 MCP in space, but you can't use the light in space and 0.00086125 lux at 189 miles for 80 MCP is not very usable, although it's still well within our threshold of low light Scotopic vision (0.00001 lux). Maybe there should be a real world CP rating (@1 lux) and a SVCP (Space Visible Candle Power) rating :thinking:

For a real world calculation in your case, you'd get 1 lux at 29,250 ft (5.539 miles) giving you 79.58 MCP, which rounds to 80 MCP anyhow. If you were to take a measurement at that distance, you'd have to use a highly accurate lux meter and zero it with the ambient light, and compensate for atmospheric blue light loss using a color temp meter.

I think it's more than fair to compensate for blue light loss with a real world CP rating because seeing the beam in the air is a huge part of the fun of these lights. On the other hand, you wouldn't compensate for blue light loss if you were only concerned with light on target, say for search and rescue missions etc. It would probably be a significant difference since these are high Kelvin lights. I think true search and rescue lights should ideally be low Kelvin so you only see the light on target and not the beam, but high Kelvin is much more fun in the sky.

Aside from all the ranting, if you get a good enough measurement at 5-1/2 miles and compensate for atmospheric blue light loss, you have yourself an 80 MCP light :thumbsup:

 

[ma_sha1]

Get lit,

How do you come up with the increased Cps? My measurement was done at 200 feet. Are you saying if I measure it at 500 feet, assuming clean & dry air, I'll gain another 15 mcp or so? I don't really need 60mcp, as long as I get to beat Ra's Maxa Blaster 52MCP portable DIY projection record, that'll be mission accomplished

As much as I love to see the numbers from your table, it doesn't behave like the inverse square law, what equation did you us? :thinking:

 

[get-lit]

Yes, you will gain according to the chart, assuming you compensate for lux loss due to atmospheric blue light scatter with distance. No, it's not the inverse square law. It's simply taking measurements at distances which reveal true candlepower. Here's an excerpt taken from the notes for my Beam Calculator...

"You may notice when taking measurements at varying distances that the beam from a parabolic reflector is not directed solely with linear divergence. The beam is a reflected image of the source, in the shape of an annulus (doughnut shape) that encircles a blurred centerline formed by the reflection diameters from the vertex hole diameter to the aperture diameter. The thickness of the annulus increases with distance, but the centerline diameter does not. The static diameter of the centerline induces a static affect on beam diameter, and with increased distance, has less affect upon total beam diameter than divergence. Therefore, measurements taken at greater distance yield greater candlepower."

 

[ma_sha1]

Ra always stated that the reflector is not fully "lit up" unless get over 100 to 200 meter distance, I never understand exactly what that means. neither is above write-up of yours, but that's OK.

Now, how do you compensate refraction loss?
I would like to use a simple equation on top of the reverse square law for CP equation, for example, a correction factor as a percentage, for a given color temp. My lamp is 8000K, what would be the % Blue Light Scattering loss ?

In your online calculator, you have P-VIP AC lamp listed in "Peak Luminous Area Concentration", but not listed as a selectable lamp type??

 

[ma_sha1]

magna light has a nice little table of data, lux measured at various distances.
I'll make some plots of cps. vs. measuring distances..

http://www.magnalight.com/absolutenm/templates/template.aspx?articleid=28&zoneid=1

 

[get-lit]

- EDITED FOR CORRECTION -

CP calculations involving the Inverse Square Law do not apply, at least directly, to lights in the real world, including flashlights, searchlights, and lasers, because the calculations do not include the distance at which the beam divergence would meet to a point behind the light. The Inverse Square Law is an approximation that becomes more accurate further from the aperture because that missing distance to the diversion point behind the light becomes less relative to distance between the aperture and point of measurement. (More info and diagrams in post #128 below)

With higher system etendue (which includes aperture diameter, vertex diameter, focal length, and luminous area), the further behind the point of divergence is located, and the further you'll have to take measurements to get more accurate CP calculations. For instance, larger apertures and smaller the luminous areas produce higher system etendue, and need to be measured further for accuracy. Lasers also have very high etendue, and likewise must be measured very far for accurate CP calculations.

This formula is supposed to address this directly:

The law for an intensity at distance "d" is I = Io(w/θ)²/(d + w/θ)²

Where:
I = intensity at distance "d"
Io = intensity at the tip of the laser
w = width of the beam at the tip of the laser
θ = beam divergence (in radians)

I've tested this and it does work, but there's two things to keep in mind.

First is that it uses the angle of the full beam as beam divergence in radians, not just the divergence of the half beam that would make a right triangle.

Second is that in order to apply this to the searchlight, you must apply it as though the "tip of the laser" is a good distance from the searchlight, say 50', and measure the diameter of the beam at that point to use as the "width of the beam at the tip of the laser". The distance "d" would then be offset by the new initial distance (50' for instance).

We could use a measured lux reading at a closer distance to extrapolate for a much larger distance which could then be used to calculate CP. The problem with this applications with a parabolic reflector, especially of short FL, is that the beam intensity is not uniform within the beam divergence (θ radians) due to the variance in reflection distance from source to reflector surface from vertex to aperture, so this will not work directly. There may be a way to make it work hopefully with some degree of accuracy but it would take a lot more thought. For now this law can help in another way.

We could still take very long distance measurements and account for atmospheric blue light refraction. Here's what I propose...

There's four factors:
1. The distance through the atmosphere
2. The density of the atmosphere due to elevation pressure
3. The relative amount of blue light in the beam
4. Our relative brightness perception of blue light

I think the best way to derive a simple atmospheric refraction compensation formula is by using a lux meter with a white laser and color filters to create various color temps. You'd take the following steps for a given altitude and white laser with a filter to match the color temperature of the light you're using:

1. Measure lux at a distance A from the laser.

2. Measure lux at a distance B from the laser.

3. Calculate how much the lux difference between A and B deviates from the "intensity at distance" law cited above.

4. Apply the deviation result to compensate for atmospheric refraction at any distance linearly relative to the distance between A and B.

 

[ma_sha1]

I plotted out the data on Magna site on those smaller HIDs.
I think it clearly shows it's necessary to measure lux at longer distances, especially for lights with higher CPs.

 

[get-lit]

In the diagram below, the green lines are the distance from the source to the lens, the blue lines are the lens to the point of lux measurement, and the red lines are the distance at which the beam divergence meets to a point behind the light. If CP is calculated using the inverse square law with the distance being from the lux measurement to the aperture, you will get significantly lower CP because the inverse square law also includes the distance from the divergence point behind the light rather than from just the aperture.

Again as system etendue increases with larger lenses and smaller light sources, the light becomes more collimated, and the divergence point extends further behind the light, further distorting CP calculations that don't account for the distance to the divergence point behind the light.

On the other hand, as the measurement distance increases, that distance increases relative to the unaccounted distance to the divergence point behind the light, and the CP calculation becomes more accurate.

Ideally, you'd just include the distance to the divergence point behind the light and you'd be set. To do this, you'd measure beam diameter at a distance relative to the aperture diameter to calculate the beam divergence angle, use the divergence angle to determine the divergence point distance behind the lens, and add that distance to the lux measurement distance from the lens, and then you're set for calculating CP using the inverse square law.

The same principle applies to reflectors, but not so well for short FL parabolic reflectors. Since the reflection distances from the source to the lens surface varies from the reflector aperture to the reflector vertex, the beam divergence angle and intensity is not consistent. You get a spot and a mini flood, and a variance of everything in between. The problem here is that since the beam divergence angles are inconsistent, so is the distance behind the light at which the beam divergence angles meet.

In the diagram below, the source light reflecting closer to the aperture has a longer reflection distance than the source light reflecting closer to the vertex. As a result, the source light reflecting closer to the aperture has less beam divergence, greater collimation, beam intensity, and divergence point distance behind the light than the the source light reflecting closer to the vertex.

I'm looking into a workable method to accurately estimate a workable divergence point distance for making a peak CP calculation with short FL reflectors. Hopefully I'll come up with something useful. I won't need to do this for my light however. Since it's a long FL, there's little variance in the source light reflection distances from aperture to vertex, with very little variance in the beam divergence angle.

 

[ma_sha1]

Bravo, Get Lit.

Thanks very much for the detailed write-up & drawings. I think I finally got it.

To put it in layman's terms:

---Inverse Square Law requires point source, Flashlight has a "pseudo point source" behind the actual surface area of light source

---CP conversion is flawed by "distance error": I.E distance used in calculation is to flashlight, but the inverse square law only applies to point source behind it.

--- Longer distance =less impact from distance error, more accurate cp measurements

 

[get-lit]

Correct. Remember, it's not the distance to the light source itself, it's the distance to the point at which the beam divergence "would" meet to a point behind the light.

I tried to come up with an easy way to make this work for short FL parabolic reflectors, by using just the inner diameter of the beam containing the peak lux, but but it's just not going to work. Unfortunately, as far as I can figure, very long distant lux measurements with compensation for atmospheric blue light scatter is the only way to accurately calculate CP for lights with short FL and even medium FL parabolic reflectors.

 

[ma_sha1]

very long distant lux measurements with compensation for atmospheric blue light scatter is the only way to accurately calculate CP for lights with short FL and even medium FL parabolic reflectors.

I am not too worried for compensation, actually, I don't want to use compensation.
Ra's 52Milion CP measurement came out of very long distance measurement, no compensation I believe, so I need to beat 52 Mil w/o compensation

 

[get-lit]

It would be nice to include the loss as a way of measuring the total beam intensity. Of course if you wanted to strictly measure beam intensity you see in the in the air, you'd be better off using a method that measures the intensity of the light reflected from just the air at a distance.

 

[get-lit]

EDIT: I used the formula I arrived at to create a calculator for determining beam divergence, the divergence point, and full candlepower with just a close distance measurement, but unfortunately it only works for lights having a uniform beam, such as lens searchlights and long FL parabolic reflector searchlights, but not medium FL nor short FL reflector searchlights.



...I also updated the more comprehensive beam calculator to include Short Arc Mercury AC Lamps, and generated some beam models I thought you'd like to compare with your beam shots...

Beam Alone (@ 200' Distance)

Beam with Data (@200' Distance) (Additional ~2MCP from your measurement could be due to atmospheric loss)

Beam with Data (@10000' Distance)

 

[ma_sha1]

Awesome !

The beam profile look very similar to what I have, bright spot with corona.
I couldn't focus it to Maxa Beam like spot only, w/o corona.

Do you know what would it take to focus into a spot only?
I bought the short EFL Parabola similar profile to Maxa Beam, just bigger.
I am wondering if Maxa Beam is not a true Parabola, rather, modified curve to accomodate non point source?

 

[get-lit]

Have you seen the Maxabeam first hand? It is a parabolic through and through and it does have a corona. Corona only shows when illuminating objects at close distance. Look at the last two beam models I made of your light. The first at 200' has a larger corona in relation to the beam center. The second at 100000' has a smaller (actually larger but much dimmer) corona in relation to the beam center. Most Maxabeam beamshots are long distance, and the corona disperses in most of what you see, just as your light would if you were to take long distance beam shots. There are some closer Maxabeam beam shots I've come across that clearly reveal its corona.

Also, the deeper the reflector (shorter FL in relation to aperture), the more concentrated the center beam, as well as larger yet dimmer corona, because there's more variance in the source to reflection distance from aperture to vertex. This is not necessarily a good thing for an intense beam. While there may be slightly more candlepower in the beam center, there's a point reached at which the beam center becomes small enough to nullify the candlepower benefit.

Consider two different configurations of the same light source; one which produces 90 MCP within a small center beam, and another that produces just 80 MCP, but within a center beam of four times the diameter. Can you guess which will produce a more intense beam in the sky? Not the one with a tad more CP. Candlepower isn't everything. That's why I devised a little trick for myself to analyze this. In the models I posted, you'll see a field I set up called Beam Power. This is not something that will go over well with the community, just my own little concept I use to compare beam intensity beyond just candlepower. Without getting into too much detail, I can assure you that the .75" FL is very well optimized for that aperture diameter and light source. You could have gone with a .6" FL and you would have gained a tad in candlepower but lost a lot in what I designate for myself as beam power, due to the significant loss in beam center diameter.

This is the reason that, even if the MaxaBlaster might have more CP than your light, your light will surely produce a more intense beam in the sky, because it contains significantly more light within the beam center relative to the difference in candlepower.

The term corona makes me want to have a drink!

 

[ma_sha1]

Have you seen the Maxabeam first hand? It is a parabolic through and through and it does have a corona.

LOL, I've had two Maxabeam, they guided me up to my Moon Blaster, at which point, they were no longer useful as reference, both were sold. See this image, top is MaxaBeam, bottom is my Led torpedo (Aspheric SST-50 over driven to 9Amp/4" AR lens).
MaxaBeam can be focused to zero corona.

In the models I posted, you'll see a field I set up called Beam Power. This is not something that will go over well with the community, just my own little concept I use to compare beam intensity beyond just candlepower.

I agree, I've calling it "Lumen in the beam" in various threads & no one seems to care. Not just make beam brighter, it actually enhance the remote target resolution quite dramatically as seen this my short arc shoot out thread, the 5MCP Mega Blaster Illuminated the target much "brighter" than the Maxa Beam of similar CPs due to 4x lumen in the beam.
http://www.candlepowerforums.com/vb/showthread.php?330370-Superlights-shoot-out-The-ShortArcs

 

[get-lit]

The Maxabeam might have a slightly deeper reflector in relation to its aperture, this would actually enlarge the corona but make it much dimmer at the same time, making it less noticeable. But I don't think this is the case. I think the Masterblaster is about on par with the Swan Blaster with relative reflector depth. There is a slight corona in that Maxabeam photo, but the camera doesn't have enough dynamic range to not blow out the center beam and show the corona at the same time. Notice in your Swan Blaster beam shots, the center beam is blown out to show the corona. If you adjust shutter speed for the center beam, the corona will fade out.

Another thing to consider is that since your dealing with so much more light with the Swan Blaster, these things become more evident.

At the moment I can't find the most revealing photos of the Maxabeam corona, but look very closely at these:

Here the camera is adjusted for the center beam and the corona is a tad dimmer, but it's there...

Here the camera is adjusted for the corona and the center beam is blown out...

"Lumen in the beam" is exactly how to describe the beam power aspect I'm talking about. You get it! It's more significant than candlepower. It was actually very easy to implement into the beam calculator. When I get a chance, I'll model the MaxaBlaster and compare Beam Power or "Lumen in the Beam" calculation and see how it correlates to the modeled beam shots. The beam centers will have similar intensities, but the Swan Blaster will have much more of it.

 

[Walterk]

@Get-Lit; Thx for the explanation on measuring cp.

 

[ma_sha1]

I'll model the MaxaBlaster and compare Beam Power or "Lumen in the Beam" calculation and see how it correlates to the modeled beam shots. The beam centers will have similar intensities, but the Swan Blaster will have much more of it.

It's a Pity that no one ever defined a perfect measurement unit for target illumination "brightness" ranking that correlate with human eyes.

I remember seeing a post that suggest using CP times lumen to represent "throw", should we call that CPL?
that may be a better measurement than CP in representing throw, in terms of effective remote target illumination brightness, which is what people have in mind when they say " throw"

otherwise laser will beat tank searchlight but it doesn't illuminate anything for useful visualization

 

[mvyrmnd]

Candlepower x Lumens x Area of target illuminated by hotspot.

That'll factor in how big the hotspot is too.

Then, you might get a lot of distance from an aspheric XR-E, but a tiny hotspot, vs the same distance from a HID with a huge hotspot, which is worth more points.

I suggest we call this new, magical unit of measurement "Square mvyrmnds"

You can use SQM for short.