Time Up for Tungsten?

January 24, 2022January 24, 2022 neilosemancinematography, equipment, gaffering, kit, LED, lighting, lighting kit, rental, sustainability, tungsten

Poppy Drayton, in “The Little Mermaid”, lit by a tungsten 1K bounced off poly

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.

Dana Hajaj lit by another tungsten 1K bounced off poly

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.

Shirley MacLaine lit by a tungsten book-light in “The Little Mermaid”

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.

5 Ways to Use Astera Tubes

July 26, 2021July 21, 2021 neilosemancinematography, fluorescent, LED, lighting, lighting effects, lighting kit

Astera Titan Tubes seem to be everywhere at the moment, every gaffer and DP’s favourite tool. Resembling fluorescent tubes, Asteras are wireless, flicker-free LED batons comprised of 16 pixels which can be individually coloured, flashed and programmed from an app to produce a range of effects.

Here are five ways in which I used Titan Tubes on my most recent feature, Hamlet. I’m not being sponsored by Astera to write this. I just know that loads of people out there are using them and I thought it would be interesting to share my own experiences.

1. Substitute fluorescents

We had a lot of scenes with pre-existing practical fluorescents in them. Sometimes we gelled these with ND or a colour to get the look we wanted, but other times it was easier to remove the fluorescent tube and cable-tie an Astera into the housing. As long as the camera didn’t get too close you were never going to see the ties, and the light could now be altered with the tap of an app.

On other occasions, when we moved in for close-ups, the real fluorescents weren’t in an ideal position, so we would supplement or replace them with an Astera on a stand and match the colour.

2. Hidden behind corners

Orientated vertically, Asteras are easy to hide behind pillars and doorways. One of the rooms we shot in had quite a dark doorway into a narrow corridor. There was just enough space to put in a vertical pole-cat with a tube on it which would light up characters standing in the doorway without it being seen by the camera.

3. Eye light

Ben Millar, Hamlet‘s gaffer, frequently lay an Astera on the floor to simulate a bit of floor bounce and put a sparkle in the talent’s eye. On other occasions when our key light was coming in at a very sidey angle, we would put an Astera in a more frontal position, to ping the eyes again and to wrap the side light very slightly.

4. rigged to the ceiling

We had a scene in a bathroom that was all white tiles. It looked very flat with the extant overhead light on. Our solution was to put up a couple of pole-cats, at the tops of the two walls that the camera would be facing most, and hang Asteras horizontally from them. Being tubes they have a low profile so it wasn’t hard to keep them out of the top of frame. We put honeycombs on them and the result was that we always had soft, wrappy backlight with minimal illumination of the bright white tiles.

5. Special effects

One of the most powerful things about Titan Tubes is that you can programme them with your own special effects. When we needed a Northern Lights effect, best boy Connor Adams researched the phenomenon and programmed a pattern of shifting greens into two tubes rigged above the set.

On War of the Worlds in 2019 we used the Asteras’ emergency lights preset to pick up some close-ups which were meant to have a police car just out of shot.

There are all kinds of other effects you could use the tubes for. There is a good example by DP Rowan Biddiscombe in this article I wrote for British Cinematographer.

“The Little Mermaid”: Prep Diary Part 2

February 8, 2021February 6, 2021 neilosemanAlexa, blog, cinematography, equipment, gaffering, grip, gripping, lighting, lighting kit, preproduction

This is the second part of my flashback to spring 2016 and the pre-production for The Little Mermaid. Part one is here.

Weeks 3 & 4

Nothing much seems to happen the third week of prep. After the Shirley shoot finishes on Monday, I take Tuesday off. I’m so exhausted I can barely move, which bodes ill for the 26-day slog of principal photography that’s coming up! Things are quiet in the office on Wednesday and Thursday, and Friday is Good Friday so it’s a holiday. The three-day weekend is enjoyable but also frustrating given how much prep there is still to do.

Next Monday I go scouting with Anthony, the new locations manager. He takes us to a quarry ten minutes down the road from the office, where we finally find the cliff we’ve been searching for since prep began. The location has a lot of potential for many scenes, so we’re very pleased. (Ultimately it went unused because of safety concerns.)

On Tuesday there’s a page turner, which is like a table read only without the cast. We spend five hours going through the script, asking questions and addressing issues that might come up. I try to clarify certain things in the script and make sure everyone knows how Chris, the director, wants to approach things. (He’s just a talking head on my iPad right now, due to visa delays.)

Gaffer Mike and key grip Jason have arrived in town for the page turner, and on Wednesday morning we get down to the business of writing a lighting list. It’s difficult for me to get my head around the crew structure here in the States. The gaffer is the head of the electrical department, so they only deal with lamps and distro. Flags, cutters, nets, black-out, bounce boards and so on are handled by the grip department, led of course by the key grip… who also handles the camera grip, like cranes and dollies.

Most of the rest of the week is spent visiting locations with Anthony, Mike and Jason, while the latter two finesse the list and get quotes. On Wednesday evening I convene the camera department to debrief from the Shirley shoot and discuss what can be done to improve the crew structure, equipment package and workflow.

By the weekend it stills feel like there is much to figure out, and there is only one week left before principal photography begins. Still, I won’t be sorry to say goodbye to office work and get back on set.

Week 5

It’s the last week of preproduction and we should be spending it doing tech scouts and production meetings. But unfortunately many HoDs have been hired late, and there are lots of locations left to find, so it’s a frustrating week for me, waiting for stuff to happen. I try to nail down the grip and electrical items which are only required on specific dates, but it looks like some of that will have to be done as we go along.

I spend more time location scouting with Anthony, during which I realise just how time-consuming it is to drive around, spot possible places, make friends with the owners and just get to the stage where any of the crew can check it out.

We visit a possible beach location, a nice little spot on the same island we did the Shirley Shoot on. Chris, still unable to enter the US, participates by video call. He wants me to roll up my trousers and test the water, because the principal cast will have to spend hours in it. It’s nice enough for a paddle, but I don’t think I’d want to spend a day up to my waist in it. (Actually, that’s exactly what I and several other cast and crew end up doing.)

As the week goes on I spend less and less time at the office, because there simply isn’t much left I can do. I occupy my evenings swimming in the pool and binge-watching season one of Outlander, which Starz have made free for a couple of weeks here in the US. The cinematography in the first couple of episodes is utterly stunning, in fact it’s the most beautiful cinematography I’ve ever seen. It’s very inspirational, and I have a couple of good ideas for lighting A Little Mermaid as I watch it. (Recently I had the exciting chance to ask David Higgs BSC about lighting the Outlander pilot, for an article in the January issue of British Cinematographer.)

Chris finally arrives on Saturday, two days before the shoot. In the evening there’s a “pre-game” party by the pool. It finally feels like we’re making a movie. The equipment has all arrived, and there are trucks and trailers parked outside the production office.

On Sunday we do the closest we’re going to get to a tech scout. It’s great to be able to walk around a location with the directors at last. (Writer Blake has joined Chris as a co-director.) I try to use Helios, a sun tracker app, to work out when the sun will hit the back of the house, but in the end I trust my own estimation better. I whip out my light meter to check the contrast ratio between sunlight and shade; it’s 8:1 (3 stops), well within the Alexa’s dynamic range, but setting up an ultrabounce to fill in the shadows, as the key grip suggests, will make the image much more pleasing to the eye.

I figure out the broad strokes of the lighting for the interiors and let the G&E (grip and electric) team know the plan. With Larry, the 1st AD, I discuss how we’re going to maximise our two cameras in order to make our day.

I can’t believe we’re about to start principal at last. Five weeks is by far the longest prep time I’ve ever had for a movie. It’s feels like I’ve been here forever! But I’m only halfway through my time in Savannah…

Here are links to my diary entries from the shoot:

“Shooting Shirley” – the pre-shoot with Hollywood legend Shirley MacLaine
“Circus Cinematography” – lighting the huge night exteriors
“Pools of Light” – creating a watery, magical look for the mermaid’s scenes
“Boats, Trains and Automobiles” – shooting in moving vehicles
“Lighting from the Back” – using cross-backlighting for cinematic dialogue scenes
“Sun, Sea and Cinematography” – filming in the ocean at sunset

The Little Mermaid is currently available on Netflix around the world.

“The Little Mermaid”: Prep Diary Part 1

February 1, 2021February 1, 2021 neilosemanAlexa, blog, cinematography, equipment, gaffering, grip, gripping, lighting, lighting kit, preproduction

I’ll soon be starting five weeks of prep for a feature, and it’s got me thinking about the five weeks I spent in the spring of 2016 prepping The Little Mermaid. I published a number of entries from my production diary when the film was released, but the entries from pre-production have gone unseen… until now…

JANuary 12th, 2016

It is four or five months since Chris, the director, first mentioned the project to me. In that time he has been developing the script with the writer and producers, and I’ve read a draft or two. Last week I was introduced to the producers by email, and today Chris and I get together to start chatting about the film.

It’s just broad strokes today, nothing structured, nothing firm. He talks me through the next round of script changes and we watch some bits of DVDs I’ve brought. I’m not thinking photographically yet, just tone and genre, so we watch parts of The Rocketeer and Big Fish. I start to get some basic ideas of what Chris does and doesn’t like.

Yesterday I went to the library to get my head around the geography of the state our story is set in, and bit of the history and culture. I found a book called Photographing America and it has some interesting plates from the Deep South in the 30s and 40s. They set the stage for me in terms of architecture, landscape and clothing, but their gritty black and white photography is not appropriate for this film.

Chris and I Skype Fabio, the line producer, and later have a brief conference call with producers Armando and Rob. At this stage it is just about introductions. Chris enthuses about me to them, and curates some stills from Ren: The Girl with the Mark to wow them with. Armando responds positively – it’s just the look he’s after for this. Well, this is the second feature job Ren’s got me. Cheers, Kate!

Week 1

Since that day in London with Chris, I’ve done bits and pieces of prep around finishing up post on Ren. The script went through a few more drafts, I joined in a few conference calls with members of the team, and started a shot list.

But on March 5th I fly into Savannah, Georgia and I’m straight into full-time prep, living and breathing A Little Mermaid.

On Sunday I wake early, my body still five hours ahead of US East Coast Time. After talking to Chris, who’s still in the UK due to visa delays, I take a ten-minute walk through the sunny streets of Savannah to meet David, the storyboard artist. We eat blueberry pancakes with maple syrup and he shows me his boards for the movie’s finale. Chris Skypes in and we discuss the priorities. We need about 15 more sequences boarded – at least key frames – ASAP so that production designer Jay can be sure to accommodate our needs in the sets he is already starting to build.

At noon I head over to an apartment complex where Jay and line producer Fabio are staying. This place has a pool so I’m getting myself moved here as soon as I can. We spend seven or eight hours, with Chris on Skype, going through the schedule line by line, making sure everything is doable and everything is in the most efficient order.

Poppy Drayton is playing our mermaid. Back at the apartment I watch a trailer for The Shannara Chronicles and screen-capture all her close-ups. I analyse the lighting in each one, labelling them accordingly in a folder. Her time on this production is limited so I probably won’t get to camera-test her; I need to figure out how to light her based on what other DPs have done.

Monday is my first day at the warehouse. It’s an old supermarket that’s been gutted. There are four or five small offices and then a huge open space, part of which is occupied by the bones of the “rocky pool” set.

The week soon settles into a blur of video calls with Chris, interviews with potential camera assistants and gaffers, and lots of discussions about sets and locations. It’s really exciting to be shown around the space by Jay as he describes all the sets he’s going to build. For some scenes there is a lot of back and forth about whether they should be studio or location. We are working with a child actress and Chris is very keen to get the best performances, so the level of control we could get in the studio is very appealing, but that must be balanced against our art department budget.

I’m assigned an office that’s just 6ft square but is very cool because it has a sort of camera obscura in the door so I can see a little projection of what’s outside. Of course the door doesn’t really close properly (particularly once I’ve run an extension cable in to compensate for the lack of functioning power sockets in the room) but never mind. By mid-week I have a monitor to hook my Mac Mini up to and I’m properly in business.

I task the PAs with printing out the script and taping it in a long line of pages along a wall along with the corresponding storyboards. Eventually we will add reference images and concept art, if I can ever get access to a functioning colour printer!

A little bit of location scouting takes place during the week. We check out a nice rustic field behind the studio where we’ll set up our circus, we visit a fort in the hope that it might work for a scene near the finale (it doesn’t) and I take a look around the beach house we’ll be shooting the film’s present-day book-ends in on March 20th and 21st. (Principal photography starts April 11th.)

Another issue to be decided is which camera to shoot on. Initially we discussed having lots of cameras, which meant going with Reds for budgetary reasons. The Panasonic Varicam is suggested, and I’m almost flown to Atlanta to test it, but in the end we decide to go with Alexas, thank God. (With hindsight, I really should have gone and tested that Varicam. I was irrationally against all non-Alexa cameras at this time.) We’ll have two bodies, one for me and one for a B camera operator who will sometimes splinter off into a 2nd unit. The glass will be Cooke S4s with a half Soft FX filter, the exact same recipe as Heretiks. I know this will give me the organic, period feel that A Little Mermaid needs, as well as the magical quality. We’ll also have a couple of Optimo zooms in the kit, a luxury we couldn’t afford on Heretiks.

By the end of the week I’ve pretty much locked down the camera kit, finished the shot list for the whole movie, and hired 1st and 2nd ACs and a 2nd Unit DP. We still don’t have a gaffer, which is worrying. The crew pool in Savannah is not huge and we’re struggling to find people with enough experience.

On Saturday, aside from a couple of hours in the studio, I chill out. I’ve now moved to the same apartment complex as the rest of the crew, and I’ve just had a very nice dip in the pool. I think I might just have the best job in the world.

Week 2

At the end of this week we have our two-day “pre-shoot” with Shirley MacLaine, to capture the contemporary bookends to what is otherwise a 1930s story. Peter Falk’s scenes in The Princess Bride are an inevitable reference for these.

Director Chris is still having visa issues, so writer Blake will be on helming duty for the pre-shoot. He gives me Maggie Smith’s storytelling scene in Hook as a reference. I haven’t seen the movie in ages, so I rent it and watch the whole thing, delighting in the beautiful cinematography. I love the candy blues and hot pinks of Wendy’s London home, and will aim to emulate them.

A lot of this week is taken up with locking down equipment and personnel for the pre-shoot. The biggest issue as the week opens is that I still don’t have a gaffer. With my options limited – and despite a brief panic during which flying my UK gaffer out here seems like a very real possibility – I pick someone on a trial basis. If they do a good job for the pre-shoot they’ll get hired for principal.

Because the gaffer is hired so late, putting together a lighting list is my responsibility. I hate doing this, because I always forget stuff and piss everyone off at the last minute by making additions or changes. Like forgetting to check whether the HMIs are pars or fresnels. (I always want fresnels because they produce better shafts of light.)

With equipment and crew in place, my attention turns towards principal for a little while. The VFX supervisor, Rich, has flown in from LA, and together we scout some locations. Unfortunately none of the locations are locked yet and the options we are given to look at are far from ideal. But we have a good session going through the shot list together, checking that there aren’t any VFX requirements that he missed in his breakdown.

We also discuss shooting format, which is generally going to be 2K ProRes 4444. He wants me to shoot green-screen shots in Arri Raw, but after he’s gone I realise that we don’t have the right Codex on our cameras for that. 3.2K ProRes will have to do. Another good tip Rich gave me is to expose the green-screen at key (i.e. the same light reading on the green-screen as on the talent’s face) or up to half a stop over.

I’m glad I invested in a light meter, which arrived at the studio this week. It also comes in handy during another scout of the pre-shoot location. We have some night shots on the beach, which will have to be shot at dusk because it’s too big an area to light artificially. During the scout I take light readings on the beach at dusk, and determine that we have until 7:50pm, 20 minutes after sunset, before it is too dark to shoot.

If you want to follow the chronology, my diary entries about the “pre-shoot” are here.

Tune in next week for my diary entries from the remaining three weeks of prep. The Little Mermaid is still on Netflix if you fancy checking it out.

5 Ways to Fake Firelight

October 5, 2020October 5, 2020 neilosemancinematography, firelight, fx, gaffering, lighting, lighting effects, lighting kit, special effects

Real SFX run a fishtail on the set of “Heretiks”

Firelight adds colour and dynamism to any lighting set-up, not to mention being essential for period and fantasy films. But often it’s not practical to use real firelight as your source. Even if you could do it safely, continuity could be a problem.

A production that can afford an experienced SFX crew might be able to employ fishtails, V-shaped gas outlets that produce a highly controllable bar of flame, as we did on Heretiks. If such luxuries are beyond your budget, however, you might need to think about simulating firelight. As my gaffer friend Richard Roberts once said while operating an array of flickering tungsten globes (method no. 3), “There’s nothing like a real fire… and this is nothing like a real fire.”

1. Waving Hands

The simplest way to fake firelight is to wave your hands in front of a light source. This will work for any kind of source, hard or soft; just experiment with movements and distances and find out what works best for you. A layer of diffusion on the lamp, another in a frame, and the waving hands in between, perhaps?

Visit my Instagram feed for loads more diagrams like this.

One of my favourite lighting stories involves a big night exterior shot from The First Musketeer which was done at the Chateau de Fumel in the Lot Valley, France. We were just about to turnover when a bunch of automatic floodlights came on, illuminating the front of the chateau and destroying the period illusion of our scene. We all ran around for a while, looking for the off switch, but couldn’t find it. In the end I put orange gel on the floodlights and had someone crouch next to each one, wiggling their hands like a magician, and suddenly the chateau appeared to be lit by burning braziers.

2. Wobbling Reflector

This is my go-to technique – quick, easy and effective. It’s demonstrated in my Cinematic Lighting course on Udemy and also in this episode of Lensing Ren:

All you need is a collapsible reflector with a gold side, and an open-face tungsten fixture. Simply point the latter at the former and wobble the reflector during the take to create the flickering effect.

3. Tungsten Array

If you want to get more sophisticated, you can create a rig of tungsten units hooked up to a dimmer board. Electronic boxes exist to create a flame-like dimming pattern, but you can also just do it by pushing the sliders up and down randomly. I’ve done this a lot with 100W tungsten globes in simple pendant fittings, clipped to parts of the set or to wooden battens. You can add more dynamics by gelling the individual lamps with different colours – yellows, oranges and reds.

John Higgins’ 2MW firelight rig from “1917”

Larger productions tend to use Brutes, a.k.a. Dinos, a.k.a. 9-lights, which are banks of 1K pars. The zenith of this technique is the two megawatt rig built by gaffer John Higgins for Roger Deakins, CBE, BSC, ASC on 1917.

4. Programmed L.E.D.

Technological advances in recent years have provided a couple of new methods of simulating firelight. One of these is the emergence of LED fixtures with built-in effects programmes like police lights, lightning and flames. These units come in all shapes, sizes and price-ranges.

Philip Bloom’s budget fire-effect rig on location for “Filmmaking for Photographers”

On War of the Worlds: The Attack last year, gaffer Callum Begley introduced me to Astera tubes, and we used their flame effect for a campfire scene in the woods when we were having continuity problems with the real fire. For the more financially challenged, domestic fire-effect LED bulbs are cheap and screw into standard sockets. Philip Bloom had a few of these on goose-neck fittings which we used extensively in the fireplaces of Devizes Castle when shooting a filmmaking course for Mzed.

5. L.e.D. Screen

A logical extension of an LED panel or bulb that crudely represents the pattern of flames is an LED screen that actually plays video footage of a fire. The oil rig disaster docu-drama Deep Horizon and Christoper Nolan’s Dunkirk are just two films that have used giant screens to create the interactive light of off-camera fires. There are many other uses for LED screens in lighting, which I’ve covered in detail before, with the ultimate evolution being Mandalorian-style virtual volumes.

You don’t necessarily need a huge budget to try this technique. What about playing one of those festive YouTube videos of a crackling log fire on your home TV? For certain shots, especially given the high native ISOs of some cameras today, this might make a pretty convincing firelight effect. For a while now I’ve been meaning to try fire footage on an iPad as a surrogate candle. There is much here to explore.

So remember, there may be no smoke without fire, but there can be firelight without fire.

How Big a Light do I Need?

May 12, 2018March 4, 2020 neilosemancinematography, exposure, gaffering, lamps, light meter, lighting, lighting kit, photometrics, prep, preproduction

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:

where

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 Lyndon and 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.

Other manufacturers provide interactive calculators: on ETC’s site you can drag a virtual Source Four back and forth and watch the illuminance read-out change, while Arri offers a free iOS/Android app with similar functionality.

If you need to calculate an illuminance value for a distance not specified by the manufacturer, you can derive it from distances they do specify, by using the Inverse Square Law. However, as I found in my investigatory post about the law, that could be a whole can of worms.

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:

where

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!

Colour Rendering Index

May 4, 2018June 11, 2021 neilosemancolour, colour temperature, CRI, fluorescent, gaffering, HMI, LED, light, lighting, lighting kit, science

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:

Source	CRI
Sodium streetlight	-44
Standard fluorescent	50-75
Standard LED	83
LitePanels 1×1 LED	90
Arri HMI	90+
Kino Flo	95
Tungsten	100 (maximum)

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.

Demonstrating the non-continuous spectrum of a fluorescent lamp, versus the continuous spectrum of incandescent, using a prism.

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.

Conclusion

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.

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Know Your Lights: Fluorescent

September 17, 2016December 28, 2016 neilosemancinematography, daylight, equipment, fluorescent, gaffering, Kino Flo, lighting, lighting kit, tungsten

Unusually being used as practicals, in a music promo, are a 2'x4 Kino Flo (foreground, with 3200K tubes) and a Kino Flo Diva Lite (top left, with 5500K tubes). — Unusually being used as practicals, in a music promo, are a 2’x4 Kino Flo (foreground, with 3200K tubes) and a Kino Flo Diva-Lite (top left, with 5500K tubes).

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.

Robocop (1987, dir. Paul Verhoeven) - note the fluorescent strips reflected in the suit. — Robocop (1987, dir. Paul Verhoeven) – note the fluorescent strips reflected in the suit.

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:

Remote Ballast

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.

Kino Flo Tegra. You can see the integrated ballast on the back.

Built-in Ballast

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 Image 87 with a silver egg crate fitted

Top to bottom: 2900K, 3200K and 5500K tubes

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.

Pampa Light in action behind the scenes of Ren: The Girl with the Mark. You can see I've gelled it with Quarter Minus Green in an attempt to correct the CRI. — Pampa Light in action behind the scenes of Ren: The Girl with the Mark. You can see I’ve gelled it with Quarter Minus Green in an attempt to correct the CRI.

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.

Know Your Lights: HMIs

September 10, 2016December 28, 2016 neilosemancinematography, daylight, equipment, gaffering, HMI, lighting, lighting kit

18K bubble for an Arrimax 12/18 — 18K bubble for an Arrimax 18/12

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.

Arri_540817_Ballast_Electronic_2500_4000_Watts_1317042538000_325678 — Arri electronic ballast for 2.5K and 4K HMIs

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.

Adjusting an Arri Daylight Compact 1200 (a 1.2K MSR) on the set of Ashes. Photo: Sophie Black — Adjusting an Arri Daylight Compact 1.2K HMI fresnel

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.

Two 18K Silver Bullet HMI fresnels rigged to a condor crane to provide moonlight for a night exterior on The Little Mermaid

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.

Know Your Lights: Tungsten

September 3, 2016December 28, 2016 neilosemancinematography, CRI, gaffering, lamps, lighting, lighting kit, reference, tungsten

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.

This comparison of domestic bulbs against daylight shows the spectra of light they emit. — This comparison of domestic bulbs against daylight shows the spectra of light they emit, with incandescent (tungsten) and halogen producing the smoothest spectra of the artificial sources.

Tungsten lighting units can be sub-categorised by the style of reflectors and/or lenses in the heads…

Open-face

Redheads draw 800W each — Generic 800W open-face light

Unknown — Arrilite 1000, a 1K open-face light

A blonde - a basic 2,000W tungsten lamp — Generic 2K open-face light

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.

Fresnel

Mole Richardson 1K 'baby' fresnel — Mole Richardson 1K ‘baby’ fresnel

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.

On Heretiks we used numerous 300W and 650W fresnels to beef up candlelight, often placing tough-spun diffuser over them, dimming them down to warm up the colour temperature, and flickering them too.

Par (parabolic aluminised reflector)

Filmgear 4-light Minibrute — Filmgear 4-light minibrute

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.

Other

Dedo, de-e-edo. Dedo come and me want go home. — Dedolite

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.

Spacelights are wagon-wheel configurations of three or six 1K lamps inside a cylinder of diffusion material. They are normally used in large numbers to provide ambient toplight on stage. Click here for a brief video introduction to spacelights.

Jem Balls, or China balls, resemble Chinese paper lanterns. They come in 22″ (up to 1KW) and 30″ (up to 2KW) sizes and produce a very soft light which I personally find is never bright enough.

Bare bulbs (usually referred to as ‘globes‘) in pendant fittings can be hung from overhead or hidden behind set dressing, perhaps to beef up practicals. On Ren: The Girl with the Mark and other projects I hid some globes behind furniture to enhance the pool of light from candles.

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.

Neil Oseman

Director of Photography

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