While I've done a fair amount of food work and shot 300 fps with an Epic before, I'd never tried 1000 fps and never used a Phantom. That meant lots of research and preparation.
The brief from the director called for falling food and splashing water with camera employing a long macro lens and moving fast on a skater dolly. I figured I'd need enough light to shoot at an aperture of at least f/4, but for preference f/8.
For lighting I had 2 basic concerns: having enough light and making sure it didn't flicker.
At high frame rates, most lights powered be normal alternating current power will tend flicker. The rule of thumb is that when you go above 120 fps with 60Hz power and 100 fps with 50Hz power you can expect flicker.
And I thought I'd never use math after high school.
The simple way to avoid flicker at high frame rates is to light with the sun or use DC power. On this shoot neither was an option. In that case, it's a good idea to have a waveform monitor or vectorscope on set to check for flicker. Also not an option for me.
Okay. What now? Play it safe I guess. Time for some research.
CHOOSING LIGHTS
CHOOSING LIGHTS
First off, my mentor Chris Chomyn suggested looking into strobe lighting from Unilux or Claremont and possibly augmenting it with big tungsten lights.
The strobes give a super cool crispness to the image. Possibly too crisp. So you can proportionally add some big tungsten to fill it out and have a little motion blur. Chris pointed out that the big upside to strobes is that they operate a significantly lower temperatures. This is a very big deal when you're shooting food or actors. Downsides to strobes: not domestically available in Vietnam, high rental cost, and needing a to sync your light meter and camera with the strobes. No strobes for this job.
HMI's: I usually use HMI's in Vietnam due to the superior power efficiency and having a bit more juice in the blue channel. At high frame rates, HMI's can tend to flicker. As an added bonus headache, you can get phase shift from the bulbs, where, as I understand it, the brightest point on the filament moves right and left, causing some weird directional and color shifts. Arri and others make high speed ballasts that correct this, but like most specialized equipment, I'm not expecting to find it in Vietnam on a normal budget.
In my research online, I read that even without a special ballast, big HMI Fresnels might be okay but PAR's will probably flicker. The suggestion was to test each individual light you intend to use - sometimes changing the ballast or the head can add or remove flicker. Without a camera test, I decided not to chance it. In the past I've had no trouble with 300 fps, 50Hz and off-brand 2.5k HMI Fresnels. But still... No HMI's for this job.
LED's: Reportedly, LED's don't flicker if you don't dim them. f/8 at 1000fps with LED's... I've heard of the lights that can do that, but I haven't seen them. In any case, definitely not available for this job. So, no LED's.
Kino's: Reportedly, Kino ballasts cycle power so fast that they shouldn't flicker up to several thousand fps. My experience leads me to believe otherwise, even if it was most likely a maintenance issue or I had Chinese knockoffs and in the heat of the moment I didn't notice the substitution. In retrospect, a 4' 4-bulb Kino 4-select System would have been quite useful, but I wasn't taking any chances. A 4'x2' bounce did the trick instead. I would have given a good Kino system a try untested, because on two shots, if it worked it would have made that little difference only a professional will actually see, but any viewer will feel.
Excluding even more exotic options, I choose Tungsten lights. Cheap and available. Excellent.
AVOIDING FLICKER
AVOIDING FLICKER
In terms of having enough light, again shooting in the sun is the safest way to go. Since I was shooting inside, I figured I couldn't possibly have too much light while I could easily have too little, so I basically ordered as many big tungsten lights as I could get within the constraints of budget and availability.
Tungsten, A/C power and high speed; here's the conventional wisdom:
The bigger the light the less chance of flicker. For reasons not fully explained, but seeming to do with the size and cooling rate of a tungsten filament, at 60 Hz, 2k and above is considered safe. For my job using 50 Hz power, lights 5k and above are expected not to to flicker.
Of course, I found that one website from some high speed specialist company which said the safe minimums were 5k/60Hz and 10k/50Hz. Lights of that size are in short supply here. Maxi-brutes aren't much use since it's actually nine 1k globes which pretty much guarantees a flicker. Fortunately, there are a couple things that you can do with smaller Tungsten lights to help mitigate flicker.
Firstly, you can set the camera to a more open shutter angle. On a Phantom, I believe the max is 359°. Regardless, I went with a 180° shutter because that's what Chris suggested for a nice balance between sharpness and motion-blur and on the day it looked great.
Secondly, you can put your lights on separate power distribution phases. I was working with typical 3-phase 220V/50Hz power, so for every light under 10k I ordered sets of 3 and asked my best boy electric, Cuong, to wire one of each to the A, B, & C phase. For top-light I used three 6x1kW space lights. For each space light, Cuong rewired the lights so that two 1K globes were on each phase. I pushed all three space lights through a 12'x12' gridcloth and there was no flicker as far as we could tell on the histogram or in playback. Due to the heat from the floor lights, we set frame and rehearsed with just the space lights. As far as I could discern on set, separating the phases and pushing them through the diff worked a treat.
My six 5k's were similarly wired to separate phases and displayed no apparent flicker. I only had two 10k's, and they were fine too.
SETUP
SETUP
As one might expect, 68,000 watts of tungsten lighting at a distance of 3m and less generates an uncomfortable amount of heat. Even with a frame of diffusion softening every light, our lettuce lasted only three or four 10s takes before it wilted.
Here's a photo of the lighting setup.
Here's a general rundown of my lighting design: the light from right side is brighter, slightly harder and somewhat higher up while the light from the left is softer and lower.
I arranged the space lights on top in a reverse pattern from the floor lights to soften shadows. The space lights also gave enough light to let us turn off the floor lights while setting the frame and rehearsing. That let us do at least some of our work without feeling like we were inside an oven.
WRAP-UP
WRAP-UP
Other notes of interest on lighting for high-speed food photography:
1. Wrapping yourself in a light-colored towel is helpful if you find yourself standing directly in 68,000 Watts of tungsten lighting for any amount of time. Yes, I'm still finding new uses for the venerable Khăn hôi.
2. Say you've got food that needs to fall though frame in a fairly even arrangement and the props people had planned to drop it by hand, but that just isn't working out. It just so happens that a 5k shutter makes for a passable mechanical drop apparatus in a pinch. It worked out for me on this job, anyway.
3. Finally, some of the most helpful advice Chris Chomyn gave me for this job:
"Don't let your need for lots of light overshadow the quality of your lighting....remember the math and light for the desired visual effect....just use more of it in proper proportion from the right angles for your slo mo...."
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