Hackaday Prize Entry: Portable LED Flash For Photography

Photography is all about light. It’s literally right there in the name – stemming from the Greek word, photos. This is why photographers obsess over the time of day of a shoot, why Instagrammers coalesce around landmarks at sunset, and why a flash helps you take photos in darkness. Historically, flashes have worked in all manner of ways – using burning magnesium or xenon lamps for example. For this Hackaday Prize entry, [Yann Guidon] is developing a portable flash using LEDs instead.

By this point in time, you might be familiar with LEDs as flash units from your cellphone. However, [Yann] is taking this up a notch. The build is based around 100W LED modules, which obviously can pump out a lot of light. The interesting part of the build is its dual nature. The LEDs are intended to operate in one of two ways. The first is in a continuous lighting mode, running the modules well below their rated power to reduce the stress on the LEDs and power supply, and to enable the flash to run on the order of an hour. In this mode, temperature feedback will be used to control the LEDs to manage power use. The other is a pulsed mode, where the LED will be overvolted for a period of milliseconds to create a much more powerful flash.

It’s this dual nature which gives the LED-based flash a potential advantage over less versatile xenon-based units, which are limited to pulsed operation only. We can see the continuous lighting mode being particularly useful for videographers needing a compact, cheap lighting solution that can also work as a pulsed unit as well.We’re excited to see how [Yann] tackles the packaging, thermal and control issues as this project develops!

24 thoughts on “Hackaday Prize Entry: Portable LED Flash For Photography

    1. I shoot at different speeds, like 1/50s usually, so I don’t need to go too short, because the actual quantity of photons increases with time. So I intend to have a variable *duration* controlled by the flash remote. Ranging from 1/50s down to whatever I can reach…

  1. I tried something similar,I taped 6x 10W LEDs to massive IBM processor cooling alu block. Three LEDs are warm, three cool, idea is to be able to change temperature of light (like those Yongnuo 300LED lights that have half warm, half cool LEDs and you can regulate them separately via PWM). LEDs are pretty close one to another, but they still produce multiple shadows. That problem will probably require using some sort of diffusion to be usable. I choose 10W LEDs because I can run them directly from laptop battery (with CC driver ofcourse), 100W variant would require step-up.
    In any case, featured project is interesting and will probably generate some interesting solutions for DIY photographic lighting.

    1. I have large panels, capable of 60W each, and quite directive, with mixed temperature (cold+while).
      the 60 LEDs make individual spots… and the resulting color is bleak, weird.
      I chose 4500K LEDs here to have a better color rendering, so the camera can adapt.
      I suppose I’ll need some diffusion and I’ll have to design a proper filter that doesn’t absorb much AND is portable AND sturdy…
      The 100W modules are already very omnidirectional so the diffusion won’t reduce the light too much.
      I received the heatspreaders so I can start hacking soon, though the 2 remaining modules are not here yet…

      1. Phosphor takes time to absorb and release energy. Color will mostly be blue then mostly yellow when pulsing white phosphor leds with a short enough duration. RBG are better for very fast pulses.

  2. I don’t know how severe the effect is with 100 W LEDs, but high intensity LEDs in general suffer from reciprocity failure, i.e., driving with twice the power for half the time does not result in the same amount of luminous power. Their efficiency drops as power increases. Google “LED nonlinearity”.

  3. Lets not forget color rendering. xeon flashes have a continue color spectrum, leds work more like TL tubes and have color spikes. If the green of the spike is not on the same place as the green of your chip, you get strange color rendering in your picture.

      1. No. You’re not listening. Xenon flashes have a continuous color spectrum. You can’t “fix” the spikes LEDs have. That’s one advantage to flashes.

        Further: the whole point of flashes is that they’re very, very fast. At lower power levels, they have a T.1 time of a few thousandths of a second. They hit power levels of a thousand watts or more of light. You’ll *never* get that out of a couple of LED arrays.

  4. It sounds awesome in theory but I’m just worried that even with the 100watt LEDs pulsed at high power, that they just won’t be powerful enough for real professional use, especially once passed through diffusers and various light modifiers. My experience with continuous lighting is that even with a thousand watts of incandescent lights, or several large led panels, you still can’t go much below iso 400 or use the apertures you need to get really crisp images.

    I really hope I’m wrong though, it’d be awesome to see something like this workind out, I’m just afraid that even with the best led tech he can get, he’ll still get beaten out in power and color quality by even the dinkiest little xenon flash.

      1. No, we won’t. You haven’t done basic research. Canon’s hotshoe flash has, at max power, a T1 time of 1/250th of a second and pumps out about 60 joules of energy in that time period. That is FIFTEEN THOUSAND WATTS of instantaneous power.

        Drop the flash to half-power and the t1 time drops to 1/1000th of a second.

        Drop the flash to quarter power and now it’s 1/2000th of a second. It’s still pumping out ~15 joules of energy in that time period – which is 30,000W of instantaneous power.

        Drop the flash to 1/128th power, and it dumps that power in 1/20,000th of a second. That’s not a typo. 50 microseconds.

        Back to quarter-power level. How are you going to generate 30kW of power for half a millisecond?

        Answer: you’re not. You’re orders of magnitude away from ever hitting those numbers. Why do you think absolutely nobody offers a commercial “LED flash”?

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