# lighting for High speed camera



## tigerkhan (May 18, 2015)

Hi All.

I am looking for heavy duty lighting to used with Photron SA4 high speed camera. any recommendation will be appreciated. 

I tried some LEDs lights but light is just not enough when you move to higher frame rate (10,000 fps). AC lights will give flicker and with DC lights (like LEDs) i am not getting some suitable option. what i really need is some DC light with very high watts (lumen) probably upto 1000 watts will work. any suggestion?

thanks


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## FRITZHID (May 18, 2015)

Xenon short arc.


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## broadgage (Jun 17, 2015)

High wattage halogen lamps should be OK since the thick filaments of high wattage lamps do not cool noticeably between cycles of the mains supply.
I would try a single lamp of the highest cheap and readily available wattage, perhaps 2KW. If that does not produce objectionable flicker, then use more similar lamps if needed.

If a 3 phase supply is available, balancing the lamps across 3 phases will eliminate flicker.

A less power hungry option would be fluorescents on electronic ballasts and spread over 3 phases.


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## SemiMan (Jun 17, 2015)

broadgage said:


> High wattage halogen lamps should be OK since the thick filaments of high wattage lamps do not cool noticeably between cycles of the mains supply.
> I would try a single lamp of the highest cheap and readily available wattage, perhaps 2KW. If that does not produce objectionable flicker, then use more similar lamps if needed.
> 
> If a 3 phase supply is available, balancing the lamps across 3 phases will eliminate flicker.
> ...




What are you trying to illuminate and what is your budget like?

What is the frame rate you are trying to hit?

There are lots of near flickerless LED drivers, just need to find the right one. Your other low cost option is just run it off a DC lab supply. Lot's of half decent ones on EBAY. This gives lots of flexibility and you have constant current for control. You don't even need a very good one. You can run series parallel strings with high powered LEDs and put a resistor in each string for balancing. I am guessing the best efficiency is not a concern so wasting 10-20% power is not a big deal.


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## TEEJ (Jun 17, 2015)

If you use more than one source, even if one has a flicker, the other will fill in for it, etc.


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## SemiMan (Jun 17, 2015)

Unfortunately, the flicker is likely to be in sync at 2X the line rate.


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## mattw (Jun 17, 2015)

Ok, so here is what I do with some of my spare time...







[/URL]Bulb_IMG_4688 by Matt Ward, on Flickr[/IMG]



Bulb_IMG_4689 by Matt Ward



41mag_Bottle_4x6_IMG_4759 by Matt Ward



Apple_IMG_4703 by Matt Ward


H2O_Ballon_4x6_IMG_4756 by Matt Ward

I to have been looking for something that can produce light with a duration of less than 1/20,000 of a second. My best flash on lowest output will make 1/25,000 and it is just not fast enough. This leads to arc flashes, they can do 1/150,000 to 1/190,000 if they are really good units. These run upwards of $10,000! So, I have been considering building my own. This is a very dangerous undertaking ranging from very high discharge voltages, extremely high UV output, very high temps and potential for glass explosions. 

The problem I see with an LED is the time to fire or warm up if you will. There is time involved in operating the silicone junction that far exceeds the basic flash interval. The causes action to separate from static items. The first photo is a light bulb hitting concrete and preparing to explode, notice the cracks? That would be very difficult to time with additional time constraints due to flash delays.

I would really like to find some way to simulate an arc flash without the dangers or without spending 10 grand + on a commercial unit for a hobby.

Matt


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## CoveAxe (Jun 17, 2015)

> The problem I see with an LED is the time to fire or warm up if you will. There is time involved in operating the silicone junction that far exceeds the basic flash interval.



I'm not sure how the ramp-time is relevant here. Even if the ramp-time was on the order of 1/50,000 seconds (and I've never seen an LED that slow), you could just time it to start a bit earlier and turn it off a bit later. Assuming you are over-driving it for higher brightness, as long as you are not keeping it on for long periods of time (seconds or minutes), it shouldn't have damage from heat.

I would think the bigger concern for LED in high-speed photography is the low brightness compared to arc tubes.


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## mattw (Jun 17, 2015)

The ramp time for me, matters when trying to capture a 365mps bullet the instant that it leaves a barrel is very difficult to begin with. If one more variable is added the timing becomes that much more difficult. If one is looking for an event that happens 1 meter from the discharge point that is more tolerable. If I calculated it correctly, in 1/50,000 of a second a bullet at this velocity will travel .183 meters. 

If one could create a flash with adequately short duration that did not cost multiple thousands, I would be very interested. There was a panel listed on Kickstarter that claims to do it, but I am not sure if it went anywhere or not. Here it is http://www.kickstarter.com/projects/vela/vela-one-the-worlds-first-high-speed-led-flash/description. I will continue to follow this one, it is possible to budget for me with some work.


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## CoveAxe (Jun 17, 2015)

Right, I get how this is important if this is a flash tube, but LEDs are not flash tubes. You can turn on an LED at high power for several seconds or more at a time. The ramp rate doesn't matter at all. All you need to do at that point is synchronize your camera, which you are already doing.


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## mattw (Jun 17, 2015)

Ok, the misunderstanding is now clear. The above photos are taken in dark with the shutter locked open and the flash providing all of the exposure. Camera shutters are very slow, 1/8000th or if you are lucky 1/10,000th of a second. When working this way, the only thing that matters is the timing of the single pulse of light and only the duration of the light stops the action. So, basically it takes a very short pulse that is fairly linear in nature. If the output is not fast and linear, you will end up with parts of the object at a different exposure level as it moves through time.

The second image is a full power .41 magnum projectile hitting the bottle. I was able to stop the spray, but when viewing the full size image the bullet is a blur that is relatively long due to the long flash duration of 1/25000th of a second exposure.


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## CoveAxe (Jun 17, 2015)

Thanks for clearing that up, I see what you are talking about now.

But where are seeing LEDs with ~1/20,000 ramp time? I've never seen an LED that slow. They're usually in the tens of nanoseconds or faster.


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## mattw (Jun 17, 2015)

I understand that the diode is quick, but the circuit that controls the discharge must be equally fast. This winter, I may get time to try and build a circuit or 2 and see what i can make happen. I have more research to do regarding overdriving led's and which ones can handle it the best. Color temp does not matter, I can correct for that. I just need really bright.


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## CoveAxe (Jun 18, 2015)

> I just need really bright.



I alluded to it earlier, but LED is probably not the best application for this. While it's fast, it's also comparatively much less bright. There's a reason any decent camera still uses a flash tube rather than an LED. Overdriving it will help, but it still won't come close to the brightness of the tube, so you'll have to use many many more LEDs to compensate.


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## SemiMan (Jun 18, 2015)

Photostrobes are millions of lumens. Pretty much impractical for LED.


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## SemiMan (Jun 18, 2015)

Hoping the op posts more details.

Wrt short duration xenon strobes this is actually quite easy.

As opposed to a big strobe cap, you go with a small high quality one, I.e. film caps, etc.

Run the unit at as high a voltage as the tube can take without self triggering.

Doing this you can easily get <10usec, but keep in mind, the images will be dimmer due to the short duration. You are at the limit of the peak output of your tube though.

It may be easier to do a bunch of small tubes.

Semiman


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## broadgage (Jun 18, 2015)

Re my earlier reply, post #3, It seems that I misunderstood what the O/P wanted.
I THOUGHT that they wanted a very bright and flicker free light source so as to avoid line frequency flicker showing up on high speed filming. High wattage halogen would be ideal for this.

However it appears that what the O/P wants is a photographic flash, but brighter and with a shorter pulse than is offered by standard equipment.


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## FRITZHID (Jun 18, 2015)

broadgage said:


> Re my earlier reply, post #3, It seems that I misunderstood what the O/P wanted.
> I THOUGHT that they wanted a very bright and flicker free light source so as to avoid line frequency flicker showing up on high speed filming. High wattage halogen would be ideal for this.
> 
> However it appears that what the O/P wants is a photographic flash, but brighter and with a shorter pulse than is offered by standard equipment.



Ditto on my 1st post as well.


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## SemiMan (Jun 18, 2015)

Broadgage you are confusing the op and mattw who added his specific requirements.

Had me confused too.


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