Industry standard to lighting with flashlights

[silvan schnelli]

Is there a sort of standard or recommendation when it comes to flashlights for cinematography? A quote that stuck with me is the one from Darius Khondji in the ASC article on Se7en. 

“The flashlights were normal though a bit boosted in wattage after we shot tests. Xenon flashlights are too obvious to me.”
 

I am planning on using them as a keylight, so the ability to control CCT and a high fidelity spectrum would be ideal.

[Matthew J. Walker]

The only flashlights–to my limited understanding–that include hardware-based color temperature are light emitting diode (LED) flashlights. Unfortunately the quality of an LED varies significantly between manufacturer and there are likely very few LED flashlight manufacturers who care about color rendering, if any. Not to mention, one can be certain such a company would charge an exorbitant amount of money for one as well. Currently operating companies like Waveform Lighting and Yuji both manufacturer 99 CRI LED bulbs with high R9 values, but charge a lot per bulb. The chance of finding similar LEDs in a flashlight are slim to none and, even if, one should expect the cost to be that much higher.

A halogen flashlight would provide you with accurate color rendering at the most affordable price, although you would be sacrificing seamless color temperature flexibility. Nonetheless, depending on the wattage of the halogen lamp, you can use gel filters over the lens of the flashlight, potentially providing you with more color temperature options than any hardware-based color temperature options would even provide. One thing to keep in mind is that halogen bulbs naturally consume more power to operate and are therefore not economical. 

Unfortunately, xenon flashlights use xenon high intensity discharge (HID) lamps which (on average) have a much less precise color rendering than a xenon arc lamp for example, that produces basically perfect color rendering but could not possibly ever be manufactured in flashlight form. Since many xenon HID flashlights manufactured today are on the cooler end of color temperatures, and it is naturally easier to filter blue light than yellow light, you would thus have more success gel filtering a xenon flashlight.

In my (biased) opinion, I always opt for halogen and/or incandescent lamps whenever possible. I am biased because, In the past, I have had the terrible experience of shooting in a space where I forgot to swap out their out their practical lighting fixtures with my own incandescent bulbs and the footage came back from the lab with noticeable flickering. Not the worst form of PTSD someone could have, but still traumatic to a cinematographer nonetheless. So, both halogen and incandescent lamps guarantee close to perfect color rendering and on-camera flickering with the two should be nonexistent with a consistent power source. Sure, gel filters are a must, and there is always a balance between power and light when using tungstens, but in terms of quality of light nothing comes close to this day.

[silvan schnelli]

Thank you for the lengthy reply. I would much rather prioritize the spectral fidelity compared to the convenience of colours and as you mentioned, maybe I can gel them.

[Guillaume Cottin]

I agree with the advice to find an incandescent flashlight. The larger Maglite with four D batteries comes to mind. However most flashlights nowadays are daylight-balanced, so unless you're doing a period film, or white balancing for tungsten, it might read a bit outdated.
I would not shy away from Xenon bulbs, they have a good spectrum, and you can gel them easily to get the CCT you need. It's often more efficient to gel a daylight source to tungsten than the other way around.

What Khondji means by "boosting the voltage" is DYI replacing the original bulb by a lower wattage bulb, which will run brighter and a few hundreds Kelvin higher in color temperature, but at the cost of a decreased longevity. It's a bit involved though, and probably not worth it unless you're shooting a lot with them, like in Seven where they're a big part of the look.