Which continuous light source is best for light painting during long exposures?

Asked 7/14/2011

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I’m looking for a handheld continuous light (a torch/flashlight, not a speedlight) to selectively illuminate parts of a scene during long exposures. I want light that works well for photography, especially for light painting.

My priorities are:

  • a broad, continuous spectrum / good color rendering
  • consistent color across the beam
  • safe use with gels and shaping accessories
  • ideally a color temperature near daylight (around 5500K), if possible

Common options seem to include incandescent, halogen, xenon, LED, HID, and fluorescent. Which lighting technology is generally the most suitable for this use, and what trade-offs should I expect?

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

15y ago

2 Answers

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To cover the full spectrum, you need something that acts like a blackbody radiator (e.g. hot element in tungsten), rather than fluorescent, as you mention, since that has sharp spikes in its spectrum (as do xenon) (though there are fluorescent panel-style lighting solutions).

See examples of emission spectra

You also don't want LED, because the emission spectrum is narrow.

I'm not sure how even color temperature across a beam will vary. If the diffuser or light modifier is constructed well, there should be full symmetry in the distribution of frequencies across the beam.

A major issue that should inform your decision is how large you want the light source to be. How large is your scene?

Anything can be made a point source, if you move it far enough away from the subject, but some lights cannot be made bright enough to do this. A bright incandescent bulb is excellent for closeup portrait work (left shot in this panel lit by 60W bulb).

HMI is very expensive, but the filament is tiny and shadows are extremely sharp from this kind of lighting (it is also much closer to daylight than tungsten, in addition to being available in crazy-high power versions, which require transformers) (right panel in this shot lit by 1200W HMI). HMI gives a brilliant, near-daylight light.

Don't dismiss fluorescent out of hand. Some of the cheapest and most interesting light sources are fluorescent. For this shot, I used a round (~1.5 ft diameter) fluorescent bathroom light, and shot through it. When shot with 50/1.2 and rendered in b/w the airy quality is wonderful. Here the background was blown out with a couple of 500 Ws monoheads in the background.

If you want to diffuse the light (softbox, scrim, etc) you have to consider the temperature of the source. You can't use the same modifiers for continuous light as for flash work - they would melt.

In other words, a lot about the light source has to do with how it's packaged and shaped.

Originally by user5870. Source · Licensed CC BY-SA 4.0

user5870

15y ago

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AI Answer

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For the most natural, continuous spectrum, tungsten-based lights (incandescent/halogen) are the strongest choice. They behave much more like a blackbody radiator, so their output is smoother and more complete than fluorescent, xenon, or typical LED sources, which can have spiky or narrow spectra.

That makes tungsten/halogen a good fit if accurate color and predictable gel behavior matter most. They’re also commonly used with modifiers, though heat is a real drawback and needs to be managed.

The main trade-off is color temperature: tungsten/halogen is much warmer than daylight, not close to 5500K. So while the spectrum is good, you’ll likely need correction gels or white-balance adjustments if you want a daylight look.

Fluorescent is generally a poor match if full-spectrum output is your priority. Xenon also tends to have spectral spikes. Typical LEDs are efficient and cool-running, but their spectrum is usually less continuous than tungsten.

So, based on your priorities, halogen/incandescent is generally the best technology, with the caveat that it runs hot and is not naturally daylight-balanced.

UniqueBot

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15y ago

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