Last October, rental house VMI retired all of its tungsten lighting units as part of its mission to be a Net Zero company by 2030. I know this mainly because I am currently writing an article for British Cinematographer about sustainability in the film and TV industry, and VMI’s managing director Barry Bassett was one of the first people I interviewed.
Barry is very passionate about helping the environment and this is reflected in numerous initiatives he’s pioneered at VMI and elsewhere, but in this post I just want to discuss the tungsten issue.
I love tungsten lighting. There’s no better way to light a human face, in my opinion, than to bounce a tungsten light off a poly-board. (Poly-board is also terrible for the planet, I’ve just learnt, but that’s another story.) The continuous spectrum of light that tungsten gives out is matched only by daylight.
Tungsten has other advantages too: it’s cheap to hire, and it’s simple technology that’s reliable and easy to repair if it does go wrong.
But there’s no denying it’s horribly inefficient. “Tungsten lighting fixtures ought to be called lighting heaters, since 96% of the energy used is output as heat, leaving only 4% to produce light,” Barry observed in a British Cinematographer news piece. When you put it that way, it seems like a ridiculous waste of energy.
Without meaning to, I have drifted a little away from tungsten in recent years. When I shot Hamlet last year, I went into it telling gaffer Ben Millar that it should be a tungsten heavy show, but we ended up using a mix of real tungsten and tungsten-balanced LED. It’s so much easier to set up a LiteMat 2L on a battery than it is to run mains for a 2K, set up a bounce and flag off all the spill.
I admire what VMI have done, and I’ve no doubt that other companies will follow suit. The day is coming – maybe quite soon – when using tungsten is impossible, either because no rental companies stock it any more, or no-one’s making the bulbs, or producers ban it to make their productions sustainable.
Am I ready to give up tungsten completely? Honestly, no, not yet. But it is something I need to start thinking seriously about.
Experience goes a long way, but sometimes you need to be more precise about what size of lighting instruments are required for a particular scene. Night exteriors, for example; you don’t want to find out on the day that the HMI you hired as your “moon” backlight isn’t powerful enough to cover the whole of the car park you’re shooting in. How can you prep correctly so that you don’t get egg on your face?
There are two steps: 1. determine the intensity of light you require on the subject, and 2. find a combination of light fixture and fixture-to-subject distance that will provide that intensity.
The Required intensity
The goal here is to arrive at a number of foot-candles (fc). Foot-candles are a unit of light intensity, sometimes more formally called illuminance, and one foot-candle is the illuminance produced by a standard candle one foot away. (Illuminance can also be measured in the SI unit of lux, where 1 fc ≈ 10 lux, but in cinematography foot-candles are more commonly used. It’s important to remember that illuminance is a measure of the light incident to a surface, i.e. the amount of light reaching the subject. It is not to be confused with luminance, which is the amount of light reflected from a surface, or with luminous power, a.k.a. luminous flux, which is the total amount of light emitted from a source.)
Usually you start with a T-stop (or f-stop) that you want to shoot at, based on the depth of field you’d like. You also need to know the ISO and shutter interval (usually 1/48th or 1/50th of a second) you’ll be shooting at. Next you need to convert these facets of exposure into an illuminance value, and there are a few different ways of doing this.
One method is to use a light meter, if you have one, which you enter the ISO and shutter values into. Then you wave it around your office, living room or wherever, pressing the trigger until you happen upon a reading which matches your target f-stop. Then you simply switch your meter into foot-candles mode and read off the number. This method can be a bit of a pain in the neck, especially if – like mine – your meter requires fiddly flipping of dip-switches and additional calculations to get a foot-candles reading out of.
A much simpler method is to consult an exposure table, like the one below, or an exposure calculator, which I’m sure is a thing which must exist, but I’ll be damned if I could find one.
Some cinematographers memorise the fact that 100fc is f/2.8 at ISO 100, and work out other values from that. For example, ISO 400 is four times (two stops) faster than ISO 100, so a quarter of the light is required, i.e. 25fc.
Alternatively, you can use the underlying maths of the above methods. This is unlikely to be necessary in the real world, but for the purposes of this blog it’s instructive to go through the process. The equation is:
b is the illuminance in fc,
f is the f– or T-stop,
s is the shutter interval in seconds, and
i is the ISO.
Say I’m shooting on an Alexa with a Cooke S4 Mini lens. If I have the lens wide open at T2.8, the camera at its native ISO of 800 and the shutter interval at the UK standard of 1/50th (0.02) of a second…
… so I need about 12fc of light.
The right instrument
In the rare event that you’re actually lighting your set with candles – as covered in my Barry Lyndonand Stasis posts – then an illuminance value in fc is all you need. In every other situation, though, you need to figure out which electric light fixtures are going to give you the illuminance you need.
Manufacturers of professional lighting instruments make this quite easy for you, as they all provide data on the illuminance supplied by their products at various distances. For example, if I visit Mole Richardson’s webpage for their 1K Baby-Baby fresnel, I can click on the Performance Data table to see that this fixture will give me the 12fc (in fact slightly more, 15fc) that I required in my Alexa/Cooke example at a distance of 30ft on full flood.
If illuminance data is not available for your light source, then I’m afraid more maths is involved. For example, the room I’m currently in is lit by a bulb that came in a box marked “1,650 lumens”, which is the luminous power. One lumen is one foot-candle per square foot. To find out the illuminance, i.e. how many square feet those lumens are spread over, we imagine those square feet as the area of a sphere with the lamp at the centre, and where the radius r is the distance from the lamp to the subject. So:
b is again the illuminance in fc,
p is the luminous power of the souce in lumens, and
r is the lamp-to-subject distance in feet.
(I apologise for the mix of Imperial and SI units, but this is the reality in the semi-Americanised world of British film production! Also, please note that this equation is for point sources, rather than beams of light like you get from most professional fixtures. See this article on LED Watcher if you really want to get into the detail of that.)
So if I want to shoot that 12fc scene on my Alexa and Cooke S4 Mini under my 1,650 lumen domestic bulb…
… my subject needs to be 3’4″ from the lamp. I whipped out my light meter to check this, and it gave me the target T2.8 at 3’1″ – pretty close!
Do I have enough light?
If you’re on a tight budget, it may be less a case of, “What T-stop would I like to shoot at, and what fixture does that require?” and more a case of, “Is the fixture which I can afford bright enough?”
Let’s take a real example from Perplexed Music, a short film I lensed last year. We were shooting on an Alexa at ISO 1600, 1/50th sec shutter, and on Arri/Zeiss Ultra Primes, which have a maximum aperture of T1.9. The largest fixture we had was a 2.5K HMI, and I wanted to be sure that we would have enough light for a couple of night exteriors at a house location.
In reality I turned to an exposure table to find the necessary illuminance, but let’s do the maths using the first equation that we met in this post:
Loading up Arri’s photometrics app, I could see that 2.8fc wasn’t going to be a problem at all, with the 2.5K providing 5fc at the app’s maximum distance of 164ft.
That’s enough for today. All that maths may seem bewildering, but most of it is eliminated by apps and other online calculators in most scenarios, and it’s definitely worth going to the trouble of checking you have enough light before you’re on set with everyone ready to roll!
Many light sources we come across today have a CRI rating. Most of us realise that the higher the number, the better the quality of light, but is it really that simple? What exactly is Colour Rendering Index, how is it measured and can we trust it as cinematographers? Let’s find out.
What is C.R.I.?
CRI was created in 1965 by the CIE – Commission Internationale de l’Eclairage – the same body responsible for the colour-space diagram we met in my post about How Colour Works. The CIE wanted to define a standard method of measuring and rating the colour-rendering properties of light sources, particularly those which don’t emit a full spectrum of light, like fluorescent tubes which were becoming popular in the sixties. The aim was to meet the needs of architects deciding what kind of lighting to install in factories, supermarkets and the like, with little or no thought given to cinematography.
As we saw in How Colour Works, colour is caused by the absorption of certain wavelengths of light by a surface, and the reflection of others. For this to work properly, the light shining on the surface in the first place needs to consist of all the visible wavelengths. The graphs below show that daylight indeed consists of a full spectrum, as does incandescent lighting (e.g. tungsten), although its skew to the red end means that white-balancing is necessary to restore the correct proportions of colours to a photographed image. (See my article on Understanding Colour Temperature.)
Fluorescent and LED sources, however, have huge peaks and troughs in their spectral output, with some wavelengths missing completely. If the wavelengths aren’t there to begin with, they can’t reflect off the subject, so the colour of the subject will look wrong.
Analysing the spectrum of a light source to produce graphs like this required expensive equipment, so the CIE devised a simpler method of determining CRI, based on how the source reflected off a set of eight colour patches. These patches were murky pastel shades taken from the Munsell colour wheel (see my Colour Schemes post for more on colour wheels). In 2004, six more-saturated patches were added.
The maths which is used to arrive at a CRI value goes right over my head, but the testing process boils down to this:
Illuminate a patch with daylight (if the source being tested has a correlated colour temperature of 5,000K or above) or incandescent light (if below 5,000K).
Compare the colour of the patch to a colour-space CIE diagram and note the coordinates of the corresponding colour on the diagram.
Now illuminate the patch with the source being tested.
Compare the new colour of the patch to the CIE diagram and note the coordinates of the corresponding colour.
Calculate the distance between the two sets of coordinates, i.e. the difference in colour under the two light sources.
Repeat with the remaining patches and calculate the average difference.
Here are a few CRI ratings gleaned from around the web:
LitePanels 1×1 LED
Problems with C.R.I.
There have been many criticisms of the CRI system. One is that the use of mean averaging results in a lamp with mediocre performance across all the patches scoring the same CRI as a lamp that does terrible rendering of one colour but good rendering of all the others.
Further criticisms relate to the colour patches themselves. The eight standard patches are low in saturation, making them easier to render accurately than bright colours. An unscrupulous manufacturer could design their lamp to render the test colours well without worrying about the rest of the spectrum.
In practice this all means that CRI ratings sometimes don’t correspond to the evidence of your own eyes. For example, I’d wager that an HMI with a quoted CRI in the low nineties is going to render more natural skin-tones than an LED panel with the same rating.
I prefer to assess the quality of a light source by eye rather than relying on any quoted CRI value. Holding my hand up in front of an LED fixture, I can quickly tell whether the skin tones looks right or not. Unfortunately even this system is flawed.
The fundamental issue is the trichromatic nature of our eyes and of cameras: both work out what colour things are based on sensory input of only red, green and blue. As an analogy, imagine a wall with a number of cracks in it. Imagine that you can only inspect it through an opaque barrier with three slits in it. Through those three slits, the wall may look completely unblemished. The cracks are there, but since they’re not aligned with the slits, you’re not aware of them. And the “slits” of the human eye are not in the same place as the slits of a camera’s sensor, i.e. the respective sensitivities of our long, medium and short cones do not quite match the red, green and blue dyes in the Bayer filters of cameras. Under continuous-spectrum lighting (“smooth wall”) this doesn’t matter, but with non-continuous-spectrum sources (“cracked wall”) it can lead to something looking right to the eye but not on camera, or vice-versa.
Given its age and its intended use, it’s not surprising that CRI is a pretty poor indicator of light quality for a modern DP or gaffer. Various alternative systems exist, including GAI (Gamut Area Index) and TLCI (Television Lighting Consistency Index), the latter similar to CRI but introducing a camera into the process rather than relying solely on human observation. The Academy of Motion Picture Arts and Sciences recently invented a system, Spectral Similarity Index (SSI), which involves measuring the source itself with a spectrometer, rather than reflected light. At the time of writing, however, we are still stuck with CRI as the dominant quantitative measure.
So what is the solution? Test, test, test. Take your chosen camera and lens system and shoot some footage with the fixtures in question. For the moment at least, that is the only way to really know what kind of light you’re getting.
If you’ve ever read or been taught about lighting, you’ve probably heard of the Inverse Square Law. It states that light fades in proportion to the square of the distance from the source. But lately I started to wonder if this really applies in all situations. Join me as I attempt to get to the bottom of this…
But before we go into that, let’s get the Law straight in our minds. What, precisely, does it say? Another excellent book, Gerald Millerson’s Lighting for Television and Film, defines it thusly:
With increased distance, the light emitted from a given point source will fall rapidly, as it spreads over a progressively larger area. This fall-off in light level is inversely proportional to the distance square, i.e. 1/d². Thus, doubling the lamp distance would reduce the light to ¼.
The operative word, for our purposes, is “spreads”.
If you’d asked me a couple of years ago what causes the Inverse Square Law, I probably would have mumbled something about light naturally losing energy as it travels. But that is hogwash of the highest order. Assuming the light doesn’t strike any objects to absorb it, there is nothing to reduce its energy. (Air does scatter – and presumably absorb – a very small amount of light, hence atmospheric haze, but this amount will never be significant on the scale a cinematographer deals with.)
In fact, as the Millerson quote above makes clear, the Inverse Square Law is a result of how light spreads out from its source. It’s purely geometry. In this diagram you can see how fewer and fewer rays strike the ‘A’ square as it gets further and further away from the source ‘S’:
Each light ray (dodgy term, I know, but sufficient for our purposes) retains the same level of energy, and there are the same number of them overall, it’s just that there are fewer of them passing through any given area.
So far, so good.
Taking the Law into my own hands
During season two of my YouTube series Lighting I Like, I discussed Dedo’s Panibeam 70 HMI. This fixture produces collimated light, light of which all the waves are travelling in parallel. It occurred to me that this must prevent them spreading out, and therefore render the Inverse Square Law void.
This in turn got me thinking about more common fixtures – par cans, for example.
Par lamps are so named for the Parabolic Aluminised Reflectors they contain. These collect the light radiated from the rear and sides of the filament and reflect it as parallel rays. So to my mind, although light radiated from the very front of the filament must still spread and obey the Inverse Square Law, that which bounces off the reflector should theoretically never diminish. You can imagine that the ‘A’ square in our first diagram would have the same number of light rays passing through it every time if they are travelling in parallel.
Similarly, fresnel lenses are designed to divert the spreading light waves into a parallel pattern:
Even simple open-face fixtures have a reflector which can be moved back and forth using the flood/spot control, affecting both the spread and the intensity of the light. Hopefully by now you can see why these two things are related. More spread = more divergence of light rays = more fall-off. Less spread = less divergence of light rays = more throw.
So, I wondered, am I right? Do these focused sources disobey the Inverse Square Law?
Breaking the law
To find the answer, I waded through a number of fora.
Firstly, and crucially, everyone agrees that the Law describes light radiated from a point source, so any source which isn’t infinitely small will technically not be governed by the Law. In practice, says the general consensus, the results predicted by the Law hold true for most sources, unless they are quite large or very close to the subject.
If you are using a softbox, a Kinoflo or a trace frame at short range though, the Inverse Square Law will not apply.
The above photometric data for a Filmgear LED Flo-box indeed shows a slower fall-off than the Law predicts. (Based on the 1m intensity, the Law predicts the 2m and 3m intensities as 970÷2²=243 lux and 970÷3²=108 lux respectively.)
A Flickr forum contributor called Severin Sadjina puts it like this:
In general, the light will fall off as 1/d² if the size of the light source is negligible compared to the distance d to the light source. If, on the other hand, the light source is significantly larger than the distance d to the light source, the light will fall off as 1/d – in other words: slower than the Inverse Square Law predicts.
Another contributor, Ftir, claims that a large source will start to follow the Law above distances equal to about five times the largest side of the source, so a 4ft Kinoflo would obey the Law very closely after about 20ft. This claim is confirmed by Wikipedia, citing A. Ryer’s The Light Measurement Handbook.
But what about those pesky parallel light beams from the pars and fresnels?
Every forum had a lot of disagreement on this. Most people agree that parallel light rays don’t really exist in real life. They will always diverge or converge, slightly, and therefore the Law applies. However, many claim that it doesn’t apply in quite the same way.
A fresnel, according to John E. Clark on Cinematography.com, can still be treated as a point source, but that point source is actually located somewhere behind the lamp-head! It’s a virtual point source. (Light radiating from a distant point source has approximately parallel rays with consequently negligible fall-off, e.g. sunlight.) So if this virtual source is 10m behind the fixture, then moving the lamp from 1m from the subject to 2m is not doubling the distance (and therefore not quartering the intensity). In fact it is multiplying the distance by 1.09 (12÷11=1.09), so the light would only drop to 84% of its former intensity (1÷1.09²=0.84).
I tried to confirm this using the Arri Photometrics App, but the data it gives for Arri’s fresnel fixtures conforms perfectly with an ordinary point source under the Law, leaving me somewhat confused. However, I did find some data for LED fresnels that broke the Law, for example the Lumi Studio 300:
As you can see, at full flood (bottom graphic) the Law is obeyed as expected; the 8m intensity of 2,500 lux is a quarter of the 4m intensity of 10,000 lux. But when spotted (top graphic) it falls off more rapidly. Again, very confusing, as I was expecting it to fall off less rapidly if the rays are diverging but close to parallel.
A more rapid fall-off suggests a virtual point source somewhere in front of the lamp-head. This was mentioned in several places on the fora as well. The light is converging, so the intensity increases as you move further from the fixture, reaching a maximum at the focal point, then diverging again from that point as per the Inverse Square Law. In fact, reverse-engineering the above data using the Law tells me – if my maths is correct – that the focal point is 1.93m in front of the fixture. Or, to put it another way, spotting this fixture is equivalent to moving it almost 2m closer to the subject. However, this doesn’t seem to tally with the beam spread data in the above graphics. More confusion!
I decided to look up ETC’s Source Four photometrics, since these units contain an ellipsoidal reflector which should focus the light (and therefore create a virtual point source) in front of themselves. However, the data shows no deviation from the Law and no evidence of a virtual point source displaced from the actual source.
I fought the law and the law won
I fear this investigation has left me more confused than when I started! Clearly there are factors at work here beyond what I’ve considered.
However, I’ve learnt that the Inverse Square Law is a useful means of estimating light fall-off for most lighting fixtures – even those that really seem like they should act differently! If you double the distance from lamp to subject, you’re usually going to quarter the intensity, or near as damn it. And that rule of thumb is all we cinematographers need 99% of the time. If in doubt, refer to photometrics data like that linked above.
And if anyone out there can shed any light (haha) on the confusion, I’d be very happy to hear from you!
In this final part of the Know Your Lights series, I’m taking a look at some of the LED fixtures currently available.
LEDs (light emitting diodes) generate light through electroluminescence. When a controlled direct current is applied to the electrodes, electrons in the semi-conductor reconfigure, releasing energy as light. LEDs have been around since the early sixties, but for decades they were only capable of emitting a weak red glow, restricting their applications to things like TV standby lights and digital clocks. In recent years the brightness and colour range of LEDs has improved dramatically, making them practical alternatives to traditional light sources.
Compared with those sources – tungsten, HMI and fluorescent – LEDs are more efficient, lighter, generate less heat, have a longer life, and are less likely to break and less dangerous when they do. They are fully dimmable, without the colour temperature changing, but if you wish, some fixtures allow you to alter the colour temperature with the turn of a knob.
On the down side, LED units are expensive, lack the raw power of large HMI or tungsten fixtures, and can often suffer from poor CRI (colour rendering index – see the overview for more info).
The technology is improving rapidly, and LEDs will only get better over the coming years. For now, many regard them as speciality lights, and they are almost always outnumbered by tungsten, HMI and fluorescent units in a drama lighting package. But some productions have really embraced them, an example being Guardians of the Galaxy, where many of the colourful practicals built into the sets were LEDs. Because they can be squeezed into smaller spaces than any other kind of light, and because you can get around the poor CRI by using coloured lamps, or gelling white ones, LEDs are well suited to creating practical glows from computers, control desks and other technology.
These are just a few of the LED fixtures currently on the market…
1’x1′ LitePanels are perhaps the most common LED unit. These panels have two dials on the back: one for brightness, and one for colour temperature (3200-5600K). They can be run off mains or a V-lock battery, drawing 40W to output about as much light as a 200W HMI.
I usually ask for a couple of these panels in my package, and they are great for situations like these:
As you are about to roll, you spot an area of the frame that needs a little extra splash of light. It is the work of moments to slap a battery on a LitePanel and fly it into shot.
A light needs to be situated in a tight space in the set, or in a spot which a power cable couldn’t reach without appearing in frame, or both. The fact that you can just prop these panels up against the set without worrying about them getting hot and damaging something is huge.
Wrapped in a diffuser like tough-spun or muslin, they make good fill lights or eye lights for day exterior close-ups.
They can make good TV sources, particularly if your set-up time is limited. A spark can twiddle the brightness and colour temp dials during takes to simulate changing images on the TV screen.
There are many manufacturers producing panels in 1’x1′ and other sizes, but LitePanels are the best ones I’ve encountered. However, I’ve yet to come across any LED unit with a good enough CRI to use as a key light.
A range I haven’t used is the Arri SkyPanels. Designed primarily to be rigged overhead from studio grids, they come in 30, 60 and 120cm lengths. The coolest thing about these units is that you don’t need to gel them; just punch in the Lee or Rosco code of the gel you want to use, and the light instantly changes colour!
Rosco Lite Pads go for a slightly different approach. The LEDs are arranged around the edges of these panels, and bounce off the white backing to produce a soft daylight source. They’re not very bright, and again the CRI is not great, but the range of shapes and sizes they come in mean that you can find one to fit most tricky spaces.
I used these a lot on Above the Clouds (check out the blog posts) in many different situations. Two 3″x12″ Lite Pads saw extensive use as fill/eye light, taped to the dashboard of a Fiat 500 in driving scenes. The other standard sizes are 3″x6″, 6″x6″, 6″x12″, 12″x12″ and 3″ circular. The panels themselves are stripped down, so batteries and dimmers can be sited remotely.
Rosco also makes LitePad Vectors, which are more like other brands of LED panel, with on-board dimmers and increased light output, and they can even make custom LitePads.
Several companies make small fresnels which at first glance appear to be HMIs, but are in fact LEDs. LitePanels make the Sola 6C and Sola ENG, equivalent to 200 and 100W HMIs respectively. Arri makes the L5, L7 and L10 units, which are each available in three models with differing brightness and colour-tuneability characteristics. The brightest L10 models are comparable with a 2K tungsten fresnel, while drawing a fifth of the power.
There are budget models out there too, such as the NiceFoto CE-1500Ws, which I used a little on Ren: The Girl with the Mark. As with all budget LED and fluorescent lights, the CRI is very poor, but it was useful when we lacked enough traditional fixtures.
Overall, LED fresnels are currently most relevant in scenarios where power is very limited, or portability and lack of heat is particularly important – in a nutshell, electronic news-gathering (ENG).
One of the most exciting things about LEDs is that because the individual diodes are so small, they don’t necessarily have to be housed in a fixture of any kind. LiteGear, for example, supplies LiteRibbons, which are strips of LEDs “mounted to a white backing material that is flexible, cuttable and adhesive backed”. The possibilities for these ribbons are pretty much endless. Here are some examples:
The Enterprise bridge set featured in the last three Star Trek movies has all its control panels lit by LiteRibbons.
Mad Max: Fury Road, and many other movies with driving scenes, had strips of LEDs mounted to the ceiling, window frames and pillars of the truck cab to increase the exposure inside.
The mini reactor that powers Iron Man’s suit is illuminated by LiteRibbon LEDs.
Some predict that, as LEDs get brighter, cheaper and higher in CRI, they will eventually replace every other kind of lighting. For now though, they’re just another part of the toolkit in which tungsten and HMIs, and to a lesser extent fluorescents, are the go-to tools.
There is a fifth type of lighting that is emerging too: plasma lighting, but it’s so new and so rare at the moment that I don’t feel equipped to write a post about it yet. But you can read about it over on Shane Hurlbut’s blog.
Another great blog to teach you about the many lights out there is Set Lighting, written by experienced Hollywood gaffer Martijn Veltman. His site was really useful when I was researching this series.
Of course, the most important thing is not what lights you have, but how you use them. There are many, many posts here on neiloseman.com to teach you about that. Check out the Lighting Techniques series for some basics, watch my Lensing Ren video series to see how all four types of lighting are used in practice on a real shoot, or simply search the tag ‘lighting’ for a wealth of material.
Tungsten and/or HMI lamps are usually the workhorse units of a lighting package, providing the power that is needed to key-light all but the smallest of set-ups. But they’re not right for every situation. If you don’t need the punch of a point source, and you want something a little softer, fluorescents might be the answer.
This is the third category of lighting units I’m covering in my Know Your Lights series; back up to the overview if you want to start from the beginning.
Fluorescent units use very similar technology to HMIs, with electrodes exciting a gas so that it gives off UV light. The phosphor coating on the tube absorbs the UV light and fluoresces, i.e. re-emits the light in the visible spectrum. Like HMIs, fluorescent units require a ballast to regulate the current.
One of the most notable early uses of fluorescents was in Robocop (1987). Jost Vocano, ASC chose the fixtures because the long, thin reflections looked great on Robocop’s suit. The flip side of that coin is that under certain circumstances fluorescents can make actors’ skin unpleasantly shiny. There was a scene in Ren: The Girl with the Mark where the poor make-up artist had to cake layers of powder onto Sophie Skelton to combat the shine of a Kino Flo I had set up.
One way I often use fluorescents is as a “Window Wrap”, a soft source that augments a hard HMI coming in through a window to wrap the light more pleasingly around the talent’s face. Or I’ll place a fluorescent outside the room, to represent or enhance indirect daylight spilling through a doorway.
Being soft sources, the light rays which fluorescents emit spread out widely, meaning the intensity drops off quickly as you move away from the lamp. (We refer to this as “throw”: fluorescents have little throw, whereas spotlights have a lot of throw.) For this reason they start to become pretty ineffective once you get more than about 6ft away from them, depending on the model.
Kino Flo is far and away the most common brand of fluorescent lighting used in the film and TV industry today, so apologies if the rest of this post reads a little like an advert for them. They’re not paying me, honestly!
The company was started by gaffer Frieder Hochheim and best boy Gary Swink after inventing the units for the 1987 comedy-drama Barfly (DP: Robby Müller, BVK). They required a fixture small enough to tuck into little alcoves in a bar location, without getting hot and causing damage.
Kino Flos come in two different kinds:
With these units, the lighting fixture is separate to the ballast, and they are connected by a header cable, just like HMIs. Remote units are usually referred to by two numbers, the first representing the length of the tubes in feet, and the second representing the number of tubes. So a unit with two tubes, four feet in length, is called a “4ft 2-bank”, often written as: 4’x2 (pronounced “four by two”).
The most common units are 2’x4 (a.k.a. “fat boy”), 4’x4 and 4’x2, but others are available, including “Single Flo” units and 6ft/8ft “Mega” units.
The ballasts allow you to turn individual tubes on and off as required, and also feature a switch marked either Hi/Lo or 4ft/2ft, which reduces the light output by adjusting the current waveform.
As you might expected, these models combine the fixture and ballast into a single unit. They are designed primarily for interview/ENG applications where it is more convenient to have everything in one. On drama productions it is generally preferable to have a remote fixture, which will be lighter, and a header cable running to an easily accessible ballast.
One advantage of built-in models over their remote cousins is that they are smoothly dimmable down to 5%.
Built-in units are known by names rather than numbers: “Diva-Lite” (2’x4), “Tegra” (4’x4) and “BarFly”, which resembles a swollen 1’x1′ LED panel. There is also the large “Image 87”, a 4’x8 fixture with a built-in ballast. It’s great for lighting green and blue screens because it puts out so much soft light.
Kino Flo tubes are available in five colours:
KF55 – 5500K – i.e. daylight – identified by blue end caps on the tubes
KF32 – 3200K – standard tungsten – gold end caps
KF29 – 2900K – warm tungsten – red end caps
420nm blue – an extra-saturated blue for lighting blue screens
525nm green – for lighting green screens
Kino Flos often come with plastic grids known as “egg crates” or “louvres”. Their purpose is to make the light more directional, effectively polarising it on a macro scale. They come in black, silver and “honeycomb” varieties, the latter available in 45º, 60º and 90º angles so you can choose how directional the light becomes – and, as a side effect, how much intensity you lose.
It is possible to remove the tubes and wiring from a Kino Flo housing so that the lamps can be squeezed into a tight space. For example, on The Little Mermaid we needed to see a soft blue glow emanating from a small translucent compartment in an organ. Best boy “Captain” Dan Xeller removed a 2ft Kino tube from its housing and placed it inside the compartment, running the wires out the back to the ballast.
Other than Kino Flo, another brand of fluorescent lights you may come across is Pampa Lights. They come in rugged boxes which can be interlinked to create larger banks of illumination. Unfortunately, in my experience the CRI (see overview) is not good, and they are best avoided.
The same goes even more so for the many fluorescent softbox kits available on Ebay from Hong Kong sellers. Not only are they flimsy in construction and questionable in terms of electrical safety, but the CRI of the lamps is very, very poor. If you need a cheap soft source, you would be much better off bouncing a halogen work light off a white card.
Indeed, firing an incandescent source into a bounce board will give you a better quality of light than even a Kino Flo. But a fluorescent fixture won’t make the room unbearably warm, it can emit daylight-balanced light, and it’s quicker to set up than a bounce board and the attendant flags. In a nutshell, it’s more convenient.
Next week, the Know Your Lights series concludes with a look at the fast-evolving world of LED illumination.
Following on from last week’s look at tungsten units, today we focus on HMI lighting. HMIs are more complex technology than tungsten, meaning they are far more expensive, and more prone to problems, particularly if you get a deal from a hire company and they give you older units. But they are bright and relatively efficient and because of this, and their colour temperature of 5,600K, they are by far the most popular type of light used in today’s film and TV industry when battling or mixing with natural daylight.
HMIs (hydragyrum medium-arc iodide) operate by creating an arc between two electrodes. This arc excites a gas which produces the light. In order to ignite the arc, a ballast is required. This device also regulates the current, while a special header cable connects the ballast to the light.
Ballasts come in two types: electronic and magnetic. Magnetic ballasts are cheaper, but if you are shooting at a shutter interval out of sync with the cycling of your power supply – e.g. 1/48th of a second with a 50Hz UK power supply – the HMI will appear to flicker on camera. Electronic ballasts have a ‘flicker free mode’ which converts the sine wave of the power supply into a square wave so that the arc does not extinguish at any point in the cycle. A side effect of this is that the head and/or ballast can produce humming, buzzing or squealing noises. Therefore many electronic ballasts have a ‘silent mode’ which reduces the noise but only prevents flicker at standard frame rates, not for high-speed work. In practice, flicker is rarely a problem as the shutter angles of today’s digital cameras can easily be tweaked to deal with it at common frame rates.
Like tungsten units, HMIs are available in open face, par and fresnel varieties, though the open face models are not very common. Arri, the major manufacturers of HMIs, call their daylight par fixtures ‘Arrisun’. Other HMI brands include Film Gear, Silver Bullet and K5600, which makes Jokers (see below).
Measured by their wattage, standard HMIs sizes are: 200W, 575W, 1.2K, 2.5K, 4K, 6K, 12K, 18K.
The smaller models, up to 2.5K, are fairly common on no-budget sets, because they can run off a domestic power supply and so don’t require a generator. At the other end of the scale, 18Ks are standard for daylight exterior and interior work on medium budgets and above.
Because of their power, HMIs often play a key part in night exterior lighting too. A 12K or 18K on a condor crane may be used to simulate the moon, while other HMI units, perhaps bounced or coming through a frame, might serve as sidelight or fill. By choosing to shoot at 3,200K, you automatically turn these HMI sources blue, often a desirable look for nighttime work.
There are many variants on the standard HMIs. Here are some of the more common ones.
Pocket pars are little 125W daylight pars that can be run off batteries. Before the days of LED panels, I used one of these for eye-light on a short film set in a forest in daylight. They can also make a good TV gag when bounced off a wobbling silver reflector.
Jokers are small units that come in 400W and 800W models. They can be reconfigured in various ways and even slotted into Source 4 housings (see last week’s tungsten post) to convert these units to daylight. We used a 400W joker a couple of times on Heretiks, when there was little space to rig in but we needed a fair bit of punch – like daylight through a small window.
The Arrimax range uses a hybrid of par and fresnel technology. They are lighter and more efficient than standard HMIs – the 800W model puts out almost as much light as an ordinary 1.2K, for example – but they’re more expensive to hire and don’t create the nice shafts of light that some DPs like (ahem). The model numbers are the wattage in tenths of a kilowatt: M8 (800W), M18 (1.8K), M40 (4K), M90 (9K) and the anomalously-named Arrimax 18/12 which accepts both 12K and 18K bubbles.
Helium Balloons are designed to provide a soft overhead illumination for night exteriors or high-ceilinged interiors. They come in a range of shapes and sizes, and aren’t necessarily HMIs; they can be fitted with tungsten lamps, or a combination of both.
Again, please let me know on Facebook or Twitter if I’ve missed out any of your favourite units. Next week: fluorescents.
Following on from my ‘Know Your Lights’ overview last week, today I’ll look in more detail at the first category of lamps and the various units available and when you might use them.
And that first category is incandescent lighting, commonly known as tungsten. It is the oldest, simplest and most robust lighting technology. Tungsten lamps are the cheapest to hire, the easiest to repair, and emit a smoother spectrum of light than any other artificial sources, making for the most natural skin tones. For my money, there’s no better way to artificially light a human face than by bouncing a tungsten source off polyboard.
Tungsten lighting units can be sub-categorised by the style of reflectors and/or lenses in the heads…
The simplest instruments are known as ‘open-face’ because they have no lens to focus the light. By far the most common units are the 800 Watt and 2,000 Watt models. These are often referred to as ‘redheads’ and ‘blondes’ respectively, though I strongly discourage these terms for reasons touched on here. 300W models – dubbed ‘Lilliputs’ by manufacturer Ianiro – are also available, as well as 1Ks and much larger models like the Mole-Richardson Skypan 5K and Skylite 10K.
While I have lit entire no-budget features with just open-face lights, on larger productions the uneven and unfocused nature of their light makes them a poor relation of other units on the truck. They are most likely to get fired into a bounce board or used to create a little pool of light somewhere in the deep background where finesse is not needed.
The fresnel lens was invented in the early 19th century by French physicist and engineer Augustin-Jean Fresnel in order to increase the focus and throw of lighthouse lamps. Today in the film industry, fresnel lenses can be found on tungsten, HMI and even LED fixtures.
Tungsten fresnels come in the following wattages: 150W, 300W, 650W (a.k.a. ‘tweenie’), 1K, 2K, 5K, 10K, 12K, 20K, 24K.
1Ks and 2Ks are sometimes called ‘babies’ and ‘juniors’ respectively, but confusingly those terms can also refer to whether they are the smaller location models or larger studio versions of the same wattage.
Though the fresnel lens reduces the light output a little, the beam is much more focused and can therefore create a shaft of light through smoke, which open-face lamps cannot. Hence I sometimes use tungsten fresnels to simulate hard sunlight when shooting on a stage. But beware that shadows cast by a fresnel can sometimes show up the ridges in the lens.
I often fire fresnels into bounce boards, and because their light is more focused they require less flagging to control the spill than open-face units.
Par lights use a parabolic (shaped like half a rugby ball) reflector and a lens to produce a soft-edged oval pool of light. They are extremely common in theatres, but are often used in film and TV as well.
Unlike fresnel and open-face units, par cans are referred to not by wattage but by the diameter of the bubble in eighths of an inch. So a Par 16 (a.k.a. ‘birdie’) has a 2″ bulb.
Par cans come in the following sizes: 16, 20, 36, 38, 46, 56, 64. They also come with various internal specs which affect the width of the beam.
Par cans are good for throwing shafts of light. On The Little Mermaid I used them to simulate car headlights, and as practicals (i.e. they were seen on camera) to uplight banners at the circus.
Maxibrutes (a.k.a. ‘Molepars’) are banks of multiple par 64 (1KW) lights. They come in banks of 4, 6, 9, 12 or 24. They pop up in the background of music promos quite often, because they look cool and kind of retro. I used two 9-light Maxibrutes, bounced off the tent roof, to illuminate the big top in The Little Mermaid. Some DPs like to use Maxibrutes for backlight on night exteriors. If you’re using them direct, you’ll need at least a sheet of diff to prevent multiple shadows.
Minibrutes (a.k.a. ‘fays’) are similar, but use smaller par 36 (650W) lamps.
Dedolites are compact units that use a unique lens system to produce very focussed, controllable light from (most commonly) 150W bulbs. They are widely available to hire, come with in-line dimmers, and are small and light enough to be rigged overhead or in tight spots. I often use them to beef up practicals.
Source Fours or (a.k.a. ‘lekos’) are ellipsoid reflector spotlights. They feature cutters which can be used to shape the beam, they can be hired with different lenses (some of which are zoomable), and they can be fitted with gobos to project patterns. They are good for stylised pools of light or for firing into distant bounce boards without spilling light elsewhere.
Finally, tungsten is usually the most desirable type of bulb to use in practicals. It is commonplace when shooting a daylight interior for a spark to go around replacing the energy-saver fluorescent bulbs in the table lamps with old-school tungsten ones. The colour is much nicer, the skin tones are better as noted above, and they can be dimmed to just the right level for camera.
I’m sure I’ve missed something out – please feel free to let me know on Facebook or Twitter! Next week: HMIs.
Welcome to the first in a series of posts looking at the many types of lighting instruments in use on film and TV sets today. This is not intended to be an exhaustive or comprehensive list, but it will give you a good idea of your options, particularly if you’re moving up from smaller productions – where lighting kit is mostly borrowed – to larger ones, where you’re required to submit a lighting list to a rental house.
Some of the key considerations when choosing a lamp are:
Incandescent lamps work by passing electrical current through a wire filament which becomes so hot that it glows. In the film industry they are generally referred to as ‘tungsten‘ units after the metal which the filament is made from. Common tungsten lamps include Dedolites, 1K ‘babies’ and open-face 800W and 2KW units (which have misogynous nicknames I shall not repeat here).
Pros: cheap, dimmable, extremely high CRI
Cons: very inefficient, get very hot, colour temperature changes when dimmed
Colour temperature: 3,200K
Light quality: generally hard (although certain units like Space Lights are softer)
The HMI (hydragyrum medium-arc iodide) is the most common form of high intensity discharge lamp used in the industry. It operates by creating an electrical arc between two electrodes which excites a gas. You may occasionally hear about an MSR (medium source rare-earth), which is slightly different technology, but as far as a cinematographer is concerned MSRs and HMIs are the same. They require a ballast to ignite the arc and regulate the current and voltage.
Pros: good CRI, good match for daylight, efficient
Cons: only dimmable down to 50%, expensive, heads and ballasts sometimes hum or ‘squeal’, older bulbs can vary in colour, flicker issues at certain shutter angles with magnetic ballasts
Fluorescent lamps are found almost everywhere today, as strip lights in supermarkets and offices, and energy-saver bulbs in the home. Similar in principle to HMIs, electric current causes mercury vapour to emit UV light which is translated into the visible spectrum by the phosphor coating on the tube. Kino Flo pretty much has the monopoly on fluorescent lighting for the film industry. Like HMIs, fluorescents require a ballast.
Pros: reasonable CRI from Kino Flos (appalling CRI from domestic/commercial fixtures), very efficient, get warm but not hot
Cons: limited dimming, high fall-off of light
Colour temperature: 5,500K and 3,200K tubes available
Gradually replacing tungsten as the most common lamps found on no-budget shoots, LED (light emitting diode) units contain semi-conductors that emit light when their electrons reconfigure. The technology is advancing rapidly, but there is currently a wide range of LED lamps on the market, varying greatly in price and corresponding quality.
Pros: extremely efficient, barely get warm, can run off batteries, almost fully dimmable, some models have adjustable colour temperature
Cons: CRI ranges from almost acceptable in the expensive models to downright shocking in the cheaper ones
Colour temperature: varies
Light quality: varies
Though there are other types of lighting, like xenon, metal-halide and HEP (high efficiency plasma), the above four are the main ones you will encounter on film and TV sets today. Over the next few weeks I’ll look at each of those types in more detail, listing many of the specific units available in each category and their applications.
Whilst prepping for The First Musketeer here in the south of France I was able to record this video blog showing the lighting kit we’ll be using and what it all does. If you don’t know your kinos from your dedos, or can’t can understand why a 2.5K HMI is SO much better than a 2K blonde, this vlog will shed some light [groan].
The first week of the adventure is drawing to a close, although we only started shooting two days ago, the rest of the week having been taken up by travel and prep.
After picking up the lighting kit from Panalux and Filmscape on Monday, we set off in a convoy of five vehicles first thing on Tuesday morning from High Wycombe. After a noon crossing from Dover to Dunkirk we drove all afternoon and most of Wednesday to get to Puy L’eveque, the medieval town in which we’re based.
The main task on Wednesday was to test the workflow of the Black Magic Cinema Camera kindly lent to us by gaffer Richard. This is my first time working with the BMCC and I’ll share my thoughts on it in a forthcoming vlog.
Shooting began on Thursday, coinciding with a storm which broke the sweltering hot spell and has seen pretty much continuous rain become the dominant weather since then. There were challenges with horses, generators and (as ever) time, but as of this writing we’re on schedule and everyone seems to be very happy with the footage acquired.
I’m not sure how much I’m allowed to reveal about the series and the details of what we’ve been shooting, so I’ll leave it there. Stay tuned for more video blogs.