HMI Lighting sync

[John B]

I have a possible commercial on the cards and it's shooting with the Red One, utilizing the slo-mo facility. The shots will be close ups of a drinks glass with liquid pouring, shot at 120fps at 2K. I want to use HMI or MSR lighting on flicker free. Are their any issues with this camera using this method? I had heard of normal speed sync problems with tungsten light and some generators, local power being fine. Grateful for any information.

JohnB

[Bret Weeks]

nope. Electronic ballasts will do well every time.

With tungsten fixtures, you must ensure that your power source is 60.00 hz (US) +/- .25 hz, or you might see some weirdness. Same with Mag Ballasts on HMIs.

See this. Pretty much rings true.

http://www.griptruck.com/technical/6...g%20speeds.htm

[M Hsu]

um. some of the older hmis has magnetic ballasts I believe which can be an issue.

[Barry Green]

See this. Pretty much rings true.

No, there's no "safe frame rates" with a rolling-shutter camera; instead you have to think in terms of "safe shutter speeds". Force your shutter to 1/40th or 1/60th and you should be fine. But 24fps @ 1/48th is not "safe" with a magnetic ballast; you have to force the shutter speed.

I don't know that 120fps will work out for with a magnetic ballast; it should be fine with an electronic ballast. 1/240th shutter speed wouldn't work with magnetic, but 1/120th is supposed to. 1/60th is a safer shutter speed, but you can't go faster than 60fps @ 1/60th.

[Nick Gardner]

You can't shoot faster than 60 fps with magnetic ballasts because of the 60 cycles per second nature of the lights. I have shot 180 degree shutter with Mag HMIs no problem.

As far as I can tell all the same rules apply that you have to pay attention to with any camera. If you are not familiar with shooting under discharge lighting, pick up a copy of The American Cinematographers Manual.

Cheers,

Nick

[Bret Weeks]

No, there's no "safe frame rates" with a rolling-shutter camera.

Barry- not being argumentative - but there are a few, and they tend to match the old CE charts.

Read that "pretty much" part again- then throw the camera up on a mag ballast @ 60.00hz and see for yourself-

At most of the "safe" frame rates the HMI "flicker" or phasing if you will is not apparent. However, at the off speeds, phasing and "flicker" are evident-

Power factor corrected (electronic) ballasts show no evidence of any issue, other than a strange bit of phasing evident when shooting some high speed 120fps glass breaks. These were shot under pretty high stop HMI pars and fresnels alongside a couple of Olympus Iseries rolling at 500fps in a studio setting-

loved your HVX book by the way-

bw

[Matt Garrett]

I have shot 180 degree shutter with Mag HMIs no problem.

On a red?

[Nick Gardner]

On a red?

Yes on a RED.

[Ramon Boutviseth]

I don't recommend shooting with hmi's if you are going for the high shutter speed look. we had a nightmare with them, we were fine at 1/120 of second, but if we wanted to go more .. it flickered like crazy.. We tried the CE chart but it didn't help much. I will be using tugsten lights from now on.