Erik Nordlund

Most newer flourescents and CFL's have high frequency ballasts, and should be fine. They're more efficient than the old magnetic ballasts, most of which have been replaced by now.

 

But if you do find magnetic ballasts somewhere, you have a problem. Given 60 Hz. power, they produce a light pulse on every half cycle, so you have 120 pulses per second. Shutter angle doesn't matter here like it does with CRT TV's. The critical thing is that the light pulse rate must be an integer multiple of your frame rate. With a film camera, you'd be OK with 30 x 4 = 120, or 24 x 5 = 120. Shooting 24 fps and speeding everything up 4% would work for film.

 

You'd have to shoot 24 fps on the Red as well. But on the Red, you have yet another consideration. The rolling shutter does unfortunate things with pulses of light, such as strobes. The light output of a flourescent starts at zero where the AC sine wave crosses zero, and stays there until it reaches a high enough voltage to strike an arc. For the rest of the half cycle, it follows, IIRC, Sin^2 or something like that. So, if you get dark horizontal bands at 180 degrees, you may have to open up to 360 degrees. That way the entire frame is exposed to an integer number of light pulses -- five.

 

-- J.S.

Thank you John for your extensive answer!

It's hard to do reliable tests until i get to the U.S. That's the real tricky part with this. But I guess that's the way it's gotta be.

Thanks again!

Hi everyone.

I currently work as an AC/technical magician ;) on a documentary project called Press Pause Play. In short terms the film aims to explore how artists and musicians around the world is affected by ongoing changes in how we produce and consume media. (The internet)

Anyways. For the following three weeks we will be in the US talking to different people and I'm wondering; since we're shooting 25 fps on a 180 degree shutter. (The Swedish way of doing things) What will happen to for example fluorescent lights in the US where the electrical system is 60hz? We're shooting on RED.

I've been talking to a lot of people here and no one seems to have a really good answer.

" Forum accounts that have never posted anything will be removed. If you fit that description, please visit the forum and post something."

I just want to continue being part of the club...

/Erik

Thanks guys, that's super!

Hello everyone..

Does anyone know where I can download a focus test chart for print?

You know the circular one with little triangular pieces narrowing down

towards the center of the circle...(?)

(Don't know if you got that, I have some trouble expressing myself, being swedish and all.)

I know places to buy it but they are a bit pricy, so please help!

/Erik