Looking for special lighting equipment

[MickeyKnox]

The artist I'm working asked me to try and find a special kind of lighting equipment that I'm not sure exists (he thinks it might not either) so I figured I'd ask here since Google has been no help with this.

What he originally described called for a portable, focusable/adjustable strobe that he can take with him, I asked him to elaborate further since as I understood it, strobes are basically more a powerful and complex flash and that didn't seem like the same kind of application. What he told me then was that he was basically looking for some portable variant of the Nightsun (link) lighting system that's used as helicopter search lights, he's done a lot of aerial photography at night so that's how he came to know about it.

So essentially a portable, battery pack powered, high density focusable lighting system; if anyone can point me in the right direction it would be greatly appreciated.

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[Big Mike]

Typically, you would just use some sort of modifier to 'focus' the light from a strobe. Barn doors, grids or snoots for example.

If you don't need all that much power, a lot of hot-shoe strobes have a zoom head and it wouldn't be hard to make a simple snoot for it. A lot more portable than a studio strobe with large battery pack.

[Alpha]

Some high-end manufacturers do indeed make dedicated spot-light strobes. Some of them are very powerful.

Your options will depend upon weight and price requirements. The best/most powerful spot strobe that I know of is Broncolor's PulsoSpot. It's a phenomenal light. As far as photo lighting goes, it does fall into the "portable" category, though it requires a battery pack (about the size and weight of a car battery). It is also very expensive-- in the order of several thousand dollars new. Depending upon where you live, you may be able to rent one.

Alternatively, you can attach a fresnel spot to a high-powered portable strobe.

[MickeyKnox]

Some high-end manufacturers do indeed make dedicated spot-light strobes. Some of them are very powerful.

Your options will depend upon weight and price requirements. The best/most powerful spot strobe that I know of is Broncolor's PulsoSpot. It's a phenomenal light. As far as photo lighting goes, it does fall into the "portable" category, though it requires a battery pack (about the size and weight of a car battery). It is also very expensive-- in the order of several thousand dollars new. Depending upon where you live, you may be able to rent one.

Alternatively, you can attach a fresnel spot to a high-powered portable strobe.

Thanks a lot, I'll look into it.

I guess I should have also mentioned that price is no object.

[Alpha]

You're welcome. The official PulsoSpot page is here:
http://www.sinarbron.com/bron/spots/pulsospot4.php

[Alpha]

You could also look into the Hensel StarSpot

[MickeyKnox]

Thanks a lot, I went over the information with him and he wants to find the most powerful one and rent it to see how he likes it then if all goes well he'll buy it. The main point of contention is how wide and how bright the spot will be at a distance of 100' and up in pitch black conditions. The width seems adjustable with different attachments for the PulsoSpot4 now it's just a matter of how it compares to the Nightsun for intensity.

[Alpha]

Okay. Here's the deal, and this is by my calculations. The great thing about the PulsoSpot is that it puts out 3200J at every angle. The NightSun, however, does not.

Okay so let's assume that the NightSun (by its specs) puts out 40,000,000 candlepower. Multiply by 0.981 to convert to Candelas. For every Candela, though, you only get 1.4x10^-3J. To make matters worse, the narrower your angle, the more light you lose. For example, the NightSun at 5 degrees, has about 167 times less output than at its theoretically widest angle.

So what this means, is that the best light source for you will depend upon what angle you're mostly using it at. Here's what I've worked out based upon the above math:

5 degrees: The PulsoSpot is 10.8 times more powerful.
10 degrees: The PulsoSpot is 2.4 times more powerful.
15 degrees: The PulsoSpot is 1.1 times more powerful.
20 degrees: The NightSun is 1.6 times more powerful.
25 degrees: The NightSun is 2.6 times more powerful.
30 degrees: The NightSun is 3.7 times more powerful.
35 degrees: The NightSun is 5 times more powerful.
40 degrees: The NightSun is 5.7 times more powerful.
45 degrees: The NightSun is 8.2 times more powerful.

Moral of the story: If you'll be using it at narrow angles, go for the PulsoSpot. If you're using it wide, go for the NightSun.

Hope that helps.

[Helen B]

Okay. Here's the deal, and this is by my calculations. The great thing about the PulsoSpot is that it puts out 3200J at every angle. The NightSun, however, does not.

Okay so let's assume that the NightSun (by its specs) puts out 40,000,000 candlepower. Multiply by 0.981 to convert to Candelas. For every Candela, though, you only get 1.4x10^-3J. To make matters worse, the narrower your angle, the more light you lose. For example, the NightSun at 5 degrees, has about 167 times less output than at its theoretically widest angle.

So what this means, is that the best light source for you will depend upon what angle you're mostly using it at. Here's what I've worked out based upon the above math:

5 degrees: The PulsoSpot is 10.8 times more powerful.
10 degrees: The PulsoSpot is 2.4 times more powerful.
15 degrees: The PulsoSpot is 1.1 times more powerful.
20 degrees: The NightSun is 1.6 times more powerful.
25 degrees: The NightSun is 2.6 times more powerful.
30 degrees: The NightSun is 3.7 times more powerful.
35 degrees: The NightSun is 5 times more powerful.
40 degrees: The NightSun is 5.7 times more powerful.
45 degrees: The NightSun is 8.2 times more powerful.

Moral of the story: If you'll be using it at narrow angles, go for the PulsoSpot. If you're using it wide, go for the NightSun.

Hope that helps.

I'm not sure where to begin.

You can't convert candelas to joules even if you know the efficiency (lumens per watt) of the source, one is a unit of luminous intensity (luminous power divided by solid angle), the other is a unit of energy (power times time). The dimensions are different. You have to introduce time in there somewhere, never mind solid angle.

The PulsoSpot puts 3200 J of electrical energy into the flash tube no matter what the angle is. However the total light output (in lumen seconds) does depend on the angle, just as it does with other normal fresnel spots. The more they are spotted, the more light is lost to the inside of the case (fancier optics like Dedolights counteract this to some extent). Sinar Bron's own figures show that. They quote f/90 for a 15 degree beam and f/64-1/3 for a 40 degree beam. That's over a 7:1 area ratio for a change of 2/3 stop. That means that the more you spot it, the less light (ie fewer lumen seconds) comes out.


Sorry,
Helen

[Alpha]

No need to apologize. Thanks for clarifying that. The candle power rating that the NightSun website lists for specs I know is relatively useless. They really don't list much that provides for easy comparison. I'll go back and re-do the math using efficiency figures for a 1600W xenon arc, which as far as I can tell is the only real indicator.

[Helen B]

No need to apologize. Thanks for clarifying that. The candle power rating that the NightSun website lists for specs I know is relatively useless. They really don't list much that provides for easy comparison. I'll go back and re-do the math using efficiency figures for a 1600W xenon arc, which as far as I can tell is the only real indicator.

Are you sure you know how to do the calcs? It doesn't look like it.

You need to completely revisit your PulsoSpot calcs as well as the NightSun calcs, though you already have a candela rating for the NightSun so that might be as far as you need to go for the accuracy achievable. You also need to assume a shutter speed, or a range of shutter speeds to compare the two.

There's enough information in the Sinar Bron specs to calculate approximate candela seconds at 15 degrees and 40 degrees. That will then enable an easy comparison to the maximum candela rating of the NightSun, via a range of shutter speeds. The candela rating of the NightSun is, in fact, a directly useful piece of information.

Forget the BS joule comparison - that was just nonsense, and suggests that you don't have any fundamental understanding of the principles behind what you are trying to do.

You could also do a rough-and-ready comparison of the likely overall output of the two units: lumen seconds vs lumens, correlated via shutter speed.

The ultimate decider will be the practical tests, but the calcs will give an idea of whether or not the commercially available strobes will get into the right ball park. You may not have to grapple with a comparison, a simple estimate based on the f/90 at 6-1/2 ft Sinar Bron value would be a good starting point to show whether or not it is worth taking the comparison any further.

If money really is no object, then I would be inclined to look into a purpose-built conversion of a high efficiency instrument to achieve exactly what was required. Those PulsoSpots are not designed for efficiency and they lose a lot of light.

Best,
Helen

[Alpha]

To portend that I won't be able to do the calcs because I "don't have any fundamental understanding of the principles" is a little harsh, don't you think? So I messed up the first calculation. Big deal. You're overstating the seriousness of my error. And if you're such a math whiz, then I'm sure you understand that the introduction of constants permits many unit conversions that don't appear intuitively possible.

In any event, although I apparently did make an error in my calculation above, the dimensions are not different, as you stated. One is defined in terms of the other. If you know the beam angle, conversion is possible. This is because Candelas are defined as watts/steradian, which introduces time into luminous intensity.

In any event, i'll leave this thread now, as I don't wish to nit-pick the math with you.

[Helen B]

...And if you're such a math whiz, then I'm sure you understand that the introduction of constants permits many unit conversions that don't appear intuitively possible.

In any event, although I apparently did make an error in my calculation above, the dimensions are not different, as you stated. One is defined in terms of the other. If you know the beam angle, conversion is possible. This is because Candelas are defined as watts/steradian, which introduces time into luminous intensity. ...

I'll stick to simple facts.

Candelas are not defined as watts per steradian, they are lumens per steradian. You can convert from one to the other if you know the spectral distribution of the radiation. No problem.

You can convert from candelas to lumens if you know the beam angle. You can, therefore make an approximate conversion from candelas to watts if you know the spectral properties of the source and the beam angle. No problem there. You cannot, however, then convert from watts to joules without using a time value, because the dimensions of watts (power) are most definitely not the same as those of joules (energy). The relevant time value would be shutter speed in this case. There is no one single time value that could be used to produce a universally-applicable conversion. Somewhere in the conversion you would also have to take the efficiency of the light instrument itself into account, of course.

Best,
Helen