Red One and Fluorescent Lighting

[Andrew Oxley]

Dear Forum,

I'm new to the world of RED and have an upcoming short film which we're shooting on the RED One. I just have a couple of questions about Fluorescent lighting. We're shooting in a classroom with overhead fluorescents (cool whites, seem to be 4100K), and daylight coming in thru the windows which I will add to by doing some lighting thru the window.

Question #1. For budgetary reasons I was thinking of leaving the overheads as is and probably splitting the white balance to around 5000K on the camera. Does the Red one pick up a huge green cast off fluorescent lights. At some point the lights go off and I'm just left with daylight. I thought by leaving the overheads with a slightly different colour would signal a bit more of a change when they go off?

Question #2. Post would like us to shoot at a frame rate of 23.98. I'm worried I may get flicker from the lights and wonder if shooting 24fps would be better? I was thinking of shooting 24fps with a 1/48th shutter, shooting at 4k 16x9. There is no off speed or high speed shots in the film. We may also shoot a shot of an iphone or ipad under this lighting and am also wondering if I'll get flicker off that screen?

Any help and thoughts would be greatly appreciated.

Thanks in advance,

Andrew

 

[Jonathan Pears]

Andrew

What lights are you using? I ask bacause you can get pretty good daylight timed bulbs without spending too much money, and keep all your color temperatures in the same area. If not, you will have to look at the image and see what you want to do. If you make the temperature cooler in camera to satisfy the lighting, then the daylight will have a blue edge to it. The same is the other way around with the lights. Depending on the quality of the light, you should't get too much of a green additon to the colors. Its hard to say without being there to see it.

Flicker should be able to be avioded at your current settings, again depending on the quality of the light source. If you're in the US, then we are on a 60MHZ power grid. So at the worst you will have to up the shutter to 1/60th to remove flicker.

Hope that helps...

 

[Andrew Oxley]

Hi Jonathan,

Thanks for your response. I'm using HMI lights outside the window either 4k closer or possibly an 18k a bit further away. Just to give a nice even exposure in the room and keep the daylight as a fairly similar level throughout the day. Also using some daylight balanced kinos inside the classroom. I don't mind the colour temperatures mixing a bit.

Do you think I'd be best to shot at 24 fps or 23.98. Do you think I would I be fine with either at 1/48th. If affects post and the sound recordist. would I be safer to shoot at 24fps instead of 23.98? Shooting in Canada.

Thanks for your help and input.

All the best,

Andrew

 

[Terry VerHaar]

Most modern flo lights use electronic ballasts which means there will be no visible flicker at any normal frame rate (I can't speak for 1000 fps or higher, lol)

 

[David Mullen ASC]

A lot of classrooms may be using older ballasts in their overhead fixtures so it's best to stick to 60 Hz AC "safe speeds" (assuming you are in a 60 Hz country), though 23.976 fps at 180 degrees barely falls into that. Sometimes if you are still seeing flicker (nice thing about digital, you can spot it while shooting) you might try a 144 degree shutter.

Yes, the Red camera will see the green cast in Cool Whites and while you could dial in some magenta in the camera and in post, then the daylight will go pink in comparison. But if you want the green cast, then you'll be fine. Otherwise, I'd consider at least swapping out the bulbs to Chroma 50's, which are a little closer to daylight/HMI -- they still have a touch of green and are 5000K, but are not a bad match for daylight.

 

[Andrew Oxley]

Hi David,
Thanks for your response. I'll think about the bulb changing. To be safe and avoid flicker potential do you think it would be best to shoot at 24fps, at 1/48, then if I see flicker move to 1/60. Post and the sound recordist have been asking as it affects their setup which I would need to settle on before the shoot. We are shooting in Canada.

Thanks again. All the best,

Andrew

 

[David Mullen ASC]

You should shoot at 23.976 as most people do, and yes, start out at 1/48th.

 

[Jeff Kilgroe]

Fluorescent tubes produce sharp spikes at various points in the color spectrum, predominantly green and pink wavelengths. Even so with the 4100~5600K "daylight" tubes. Just be mindful of this, so you may see some color casting in bright whites as David points out. One place many of us have encountered green or magenta spikes with fluorescent lighting is in metallic surfaces. It's pretty easy to correct out on chrome car bumpers and things of that nature. Not so easy to correct out on metallic car paints or the makeup on your actress's face! White balance in-camera is just a metadata setting and has no bearing on anything other than monitoring and as a look to apply to the RAW image. You can completely change it later in post at any time you are still referencing the RAW footage. That said, it's best to get it as close as you can to ideal when shooting, otherwise you may end up with other color problems down the road that you were unaware of during shooting. Simply thinking that magenta cast will correct out isn't always the best approach and sometimes it takes a bit more finesse or even brute force in color grading passes later on when it would have been easier to address with changes to lighting or filtration on set.

I shoot mostly corporate stuff and even with that, I still go to great lengths to not shoot in mixed color lighting. Unless it's a creative choice...

 

[Andrew Oxley]

Hi David,
Thanks for your help. Sorry maybe a dumb question. I'm shooting on the RED one and I know it gives the option of shooting at 24 or 23.98. On the Red site it says 23.98 would be safe with fluorescent at 1/60 and 24fps is safe at any angle. I'm just wondering if 24fps is safe at any angle if that would make more sense? Then I could shoot at 1/48 incase I needed the extra exposure? Post and sound seems fine either way as long as they know in advance?
Sorry to bother you but thanks for your help.
All the best,
Andrew

 

[David Mullen ASC]

I only shot 24P once on one of the first 24P movies made in 2000, "Jackpot", and we had a number of sync issues with sound in the mix, so I've avoided true 24P ever since. So I'm not going to advise you to shoot 24P.

23.98P and 24P are safe at any shutter speed more or less but 24P is slightly more safe, the window is slightly larger... but 99% of people shoot at 23.98P in those situations and are fine. But there are issues once you get near 45 degrees at either speed with pulsing 60 Hz AC lighting -- not flicker problems but exposure issues. Whether or not you are at 23.98P or 24P, at 180 degrees you are getting more or less 2.5 pulses per frame or something like that. You get exactly 2 pulses at 144 degrees (1/60th).

Look, you're lucky, you're shooting digital -- you can adjust your shutter by tenths of a degree until you get rid of the flicker and see the results live on the monitor, so don't worry so much about it.

 

[Andrew Oxley]

Thanks for that and your time. Enjoy the rest of the weekend.

 

[Stephen Pruitt]

The flicker is one issue, and it's not quite "flicker" per se that I'd worry about, but, rather, banding. That's a real bear, and you'll need to watch for it very carefully.

The best way I know of to check for those obnoxious bands in the image is to do a test shot of a blank wall lit by the room lights and then play that clip back at high speed. If there is an issue with banding, it will be very evident at high speed.

The issue with the green cast is real, but the issue of not matching the outside lights when the inside lights might have a particularly easy fix. You're shooting RAW, so just bring in two separate clips of the same shot, each correctly balanced to the appropriate light, and then stitch them together at the point that the light goes off. You might need a two-frame transition, but you'll be golden (pun intended). This isn't the time-consuming, expensive, hassle-filled correct fix of messing with all the different light colors, but it is a very simple and easy one. BUT, it will only work if the camera isn't looking toward the window when the lights get switched off (or the sunlight will suddenly change in color) and you can't try to push the balance too far.

Good luck.

Stephen