Generic Fluorescent Lamps
Posted 31 January 2012 - 12:35 PM
I'm shooting in a school hallway lit by two windows and a ceiling of fluorescent fixtures. My thought is to ND the windows, fill the fixtures with daylight bulbs, and color-balance the camera to daylight. I was wondering if anyone here has had experience with generic daylight balanced bulbs such as these. I'm worried about possible flicker and dark horizontal banding as is always the case with fluorescents. I've read on here that adjusting the shutter speed to 1/60 may help but I'd rather not do that.
I'm shooting with an AF-100 at 24p and a shutter speed of 1/50.
Thanks in advance.
Posted 31 January 2012 - 12:46 PM
Older iron ballasts may cause the problems you describe (I've seen the same problem on an iron-ballasted HMI), but modern electronic ballasts can make the lamps flicker at all kinds of odd frequencies, often in the many tens of thousands of cycles per second. Obviously this can cause all kinds of fun and games, and it is rather difficult to predict what's going to happen without just trying it.
Posted 31 January 2012 - 12:52 PM
Now, as for the floros, it doesn't matter on the bulb end aside from CRI; what matters is the ballast.
That being said, I rarely get problems with most ballasts out there so long as I'm shooting 1/48th (1/60th) 24 (30) fps. It's when you start doing off speed stuff that you run into a problem.
I would check out the CRI on those bulbs before purchasing. Best idea, and most expensive, would be to swap out Kino Tubes into the fixtures, but that's costly. Elsewise, there are some good Hi CRI 5600K tubes on the market but as to whether or not those ones are I can't say. It may be on the box, it may not be. Might we worhtwhile to shoot a message over to Phillips to get better specs.
I know Home Depot carries >90 CRI bulbs as I've foudn them there before, but I can't recall the brand; Whatever you go with, get the highest CRI possible. over 90 is ok for motion picture work, but you can get away with 85 and above if need be.
You could also just black out the overhead floros and let the daylight do what it does, working with bounces as needed. There is, of course, continuity issues in lighting that way, but may be easier than swapping out bulbs.
Posted 31 January 2012 - 01:20 PM
Posted 31 January 2012 - 04:29 PM
Good output, flicker totally dependent on ballast (but even $10 housings usually have electronic ballasts and thus no flicker these days), and good color rendering considering the price. If you have the ability to time out a minor green spike (which might not even be a problem at all) you'll be all set with these lights.
With 1/50 you may not see flickering until it's too late, especially with dSLRs. So try out some outlandish fast shutter speeds to see if the lights flicker at all. If they don't, you're good, it's an electronic ballast (which won't flicker until you get to ridiculous speeds). If they do flicker, shoot at 1/60, which should be safe unless they're malfunctioning. Sure kinoflos would be better but these will have more output and just slightly worse color.
Posted 31 January 2012 - 04:32 PM
I'm shooting in a school hallway lit by two windows and a ceiling of fluorescent fixtures. My thought is to ND the windows, fill the fixtures with daylight bulbs, and color-balance the camera to daylight.
Most shows swap out the house Flo tubes with Movie-Tone tubes (see http://www.movie-tone.com/ for available color temperatures.) Since you are already going to the effort of gelling windows and swapping out tubes, why not balance the camera for 3200K and use 85ND6 gel on the windows and 3200K Movie-tone tubes instead. This way you can use less expensive tungsten fixtures for your supplemental lighting rather than more expensive HMI or Daylight balanced Kino Flos.
As others have pointed out, flicker is a function of the ballast and not the tubes. A school may have some older magnetic ballasts which will not operate at a high frequency and so cause flicker. Even if they do operate at a high frequency, if it is not the right frequency, you can get what is callled an “eratz ripple.” Even though the ballasts put out a high-frequency cycle, that cycle stacks to create a lower frequency waveform which causes the light to pulsate. In a number of incidents, 24p video cameras and film cameras operating within a flicker-free window have picked up flicker from the “eratz ripple” effect. For this reason, the only way to know for sure is, as Phil says, shoot some tests to make sure you will not get an “eratz ripple” (use this link for more details about Flos and Flicker.)
Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip Equipment Rental and Sales in Boston.
Posted 31 January 2012 - 04:41 PM
Still Guy's sugstion of going to 3200K and saving a ton of money on rental going with tungsten heads, is very smart advice.
Posted 31 January 2012 - 06:12 PM
My main concern going 3200K with most digital systems is the inherent bias of the silicone to 5600K - give or take. On the AF, I'd want to keep the sensor as "happy" as possible as dealing with that internal compression is not always a fun experience.
There is something to Adrian’s concern. Using tungsten light sources when the camera’s native color balance is 5000K doesn’t make a lot of sense. Balancing tungsten to 5000K is not very efficient because full CTB cuts the output of the light by 70% in converting it to 5000K. A 1000W 3200K light becomes a 300W 5000K light when you put Full CTB on it. A 400 W HMI will give you considerably more lumens/watt than a color corrected Tungsten 1k, and use up a lot less power.
It makes more sense to use HMIs to light for cameras with a native color balance of 5000K because they provide more lumen/watt and require less filtration with gels, but they are also considerably more expensive to buy or rent. While Kino Flos are a cost effective alternative to HMIs, they generally have a very broad soft light output that drops off rapidly which means the units need to be positioned close to the subject they are lighting. This characteristic makes them better suited to lighting documentary interviews than dramatic scenes like the one described here. The one exception to that rule is the Kino Flo ParaBeam fixtures.
The Kino Flo ParaBeam fixtures use computer aided designed (CAD) parabolic reflectors that focus the light output at about 16 feet (5 meters). This feature makes the Kino Flo ParaBeams well suited for dramatic set lighting, because it doubles the light output of the lamps where it is needed most for lighting dramatic scenes - at a medium distance. Compared to the Kino Flo Diva-Lite, which uses the same four 55 Watt compact lamps and the same ballast, the ParaBeam 400 is twice as bright at 12' – making them a suitable key source for lighting dramatic scenes. Kino Flo also makes available for the ParaBeam fixtures a number of innovative accessories that enhance their production capabilities for HD Digital Cinema. Accessories include barndoors, a gel frame, a diffusion panel, and Honeycomb Louvers. Honeycomb Louvers are available in 90, 60 and 45 degrees and provides beam control similar to that of swapping lenses on an HMI Par.
Wide Shot of Night exterior scene lit with our HD P&P Pkg.
For example, on a recent independent short shot on a Red, I used a package that consisted of a 2.5kw, 1200, & 800 HMI Pars (with PFC ballasts), a couple of Kino Flo Parabeam 400s, a couple of Parabeam 200s, and a Flat Head 80. Given the light sensitivity of the Red Camera, this was all the light we needed to light a large night exterior (see pictures attached.)
The PFC 2.5 & 1.2 HMI Pars, PFC 800w Joker HMI, Kino Flo Flat Head 80, 2 ParaBeam 400s, and a ParaBeam 200 of our HD P&P Pkg. powered by our modified Honda EU6500is through our 60A Full Power Transformer/Distro
The scene takes place behind a mall at night, rather than a school corridor at day, but the issue of color balancing of lights to the native color balance of the camera are the same: we used the 2.5 HMI par to light the deep background, the 1200 HMI par to light the near background, and the 800 Joker was mounted on a Source 4 Leko with a bug-a-beam adapter to create a window pattern on the ground from a building that doesn’t exist but you don’t see that in the movie. We used two Parabeam 400s to key the talent and a Kino Flo Flathead 80 to fill the entire scene.
A Distro System consisting of a 60A Full Power Transformer/Distro, 2-60A GPC (Bates) Splitters, 2-60A Woodhead Box distributes power from a modified Honda EU6500is. Even though the generator is 100' away to reduce noise, plug-in points remain conveniently close to set.
We balanced the color temperature of the lights to the Red’s native 5000K color balance as follows: the 2.5 & 1200 Pars were gelled with ½ CTB for moonlight. We put half CTO on the Joker 800 to create warm window light. We mixed 3200K tubes into the Parabeam 400 on the “window” side to create a warm key source motivated by the window. The Parabeam on the other side was gelled with ¼ CTB to create a cool key source motivated by the moonlight. Finally, we lamped the Flathead 80 with only 5500K tubes to create a slightly cool fill. To see the final results, use this link to our website where we have posted more detailed information on the lighting package we used along with production stills from the movie.
- Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip Rental and Sales in Boston
Posted 31 January 2012 - 11:05 PM
The 950 burns at 5000K @ 92 CRI
The 930 burns at 3000K @ 91 CRI
We use them quite often and find they match reasonably well to Kino tubes.