Shooting Video Under LED Lighting

[Thomas Hanser]

I have to shoot in an commercial aircraft interior mockup that is lit with LED lighting, which I’ve been told has a refresh rate of 50hz.

I shot a test in this mockup with a Canon XF100, shutter speed of 1/60th. You can’t see the white rolling bars in the camera’s monitor, but you can sure see it in the timeline – the clip is virtually worthless.

The XF100 has the Clear Scan shutter feature, which allows you to dial in precise frequencies in Hertz. But without a large field monitor to work with, how can I determine what frequency to set the camera at?

Does anyone have experience shooting under these lights? What should I do under these circumstances?

Thanks in advance.

Thomas Hanser
Seattle, WA

[Todd Terry]

Hmm, well that’s going to be a little bit of a tough one.

Since your viewfinder is basically lying to you (well, maybe not lying, but is so forgiving that the image looks good when it really isn’t), I’m not sure there is any way around that other than doing at least your initial setup with a larger production monitor on location. Is that just physically impossible?

While a clearscan camera can fix the problem easily, the problem is of course knowing exactly what the shutter speed (in Hz) should be. Since you’ve been told this system is 50 Hz, and considering you are in the US, that leads me to believe it is battery powered or DC-converted using some independent system… separate from “mains” power. Ergo, we don’t know what the heck the actual precise Hz shutter speed should be. They may tell you it’s 50 Hz, but as I’m sure you know it is highly unlikely to be exactly 50… it’s probably something like 50.023 or 49.985 or some other seemingly random number… but one that you must hit on exactly to completely eliminate the strobing.

I just can’t think of a single way to set this up with known accuracy without having a truthful monitor, at least for the initial setup.

Also, not to stir the pot further, but there might be multiple frequencies going on there. I was shooting a location once that had several hundred decorated Christmas trees… all with LED lighting. Because multiple generators were being used to power these, not all of the trees could be shutter-synced at once. I could dial in a precise shutter speed for one section of trees, and another section would strobe… and vice versa. Maybe not, but you might run across this same phenomenon with your aircraft lighting. In that case you’d need a truthful monitor not only for the initial setup, but for all shots.

Anyone else have a better (or smarter) solution?

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com

[Thomas Hanser]

Todd: what a spot on and truthful comment and reply.

I’m planning on going back and shooting another test, this time with the camera Shutter setting on LOW. This allows me to dial in slower shutter speeds from 1/30th down to about 1/4. Maybe one of those speeds will reduce the rolling white bands I get.

If I shot individual clips at different slower speeds, I could note those speeds by speaking them into the onboard mic. (I don’t think shutter speed is recorded as metadata with the clip.)

I have a Marshall Electronics monitor that fits on the camera’s hot shoe – it’s not very big, maybe 5″-6″ wide, but I’ll try that and see if it shows the white banding. How big of a field monitor do you need to show a flicker problem like this?

The bands, BTW, are really soft-edged, not hard like you see in some situations.

Thanks again, Todd.

Thomas Hanser
Seattle, WA

[Mark Suszko]

You say it’s a mock-up… maybe the lights are on dimmers you can access and crank up to full? Then adjust iris to compensate?