Colour temperature starts with something mysterious called a “black body”, a theoretical object which absorbs all frequencies of electromagnetic radiation and emits it according to Planck’s Law. Put simply, Planck’s Law states that as the temperature of such a body increases, the light which it emits moves toward the blue end of the spectrum. (Remember from chemistry lessons how the tip of the blue flame was the hottest part of the Bunsen Burner?)
Colour temperature is measured in kelvins, a scale of temperature that begins at absolute zero (-273°C), the coldest temperature physically possible in the universe. To convert centigrade to kelvin, simply add 273.
The surface of the sun has a temperature of 5,778K (5,505°C), so it emits a relatively blue light. The filament of a tungsten studio lamp reaches roughly 3,200K (2,927°C), providing more of an orange light. Connect that fixture to a dimmer and bring it down to 50% intensity and you might get a colour temperature of 2,950K, even more orange.
Incandescent lamps and the sun’s surface follow Planck’s Law fairly closely, but not all light sources rely on thermal radiation, and so their colour output is not dependent on temperature alone. This leads us to the concept of “correlated colour temperature”.
The correlated colour temperature of a source is the temperature which a black body would have to be at in order to emit the same colour of light as that source. For example, the earth’s atmosphere isn’t 7,100K hot, but the light from a clear sky is as blue as a Planckian body glowing at that temperature would be. Therefore a clear blue sky has a correlated colour temperature (CCT) of 7,100K.
LED and fluorescent lights can have their colour cast at least partly defined by CCT, though since CCT is one-dimensional, measuring only the amount of blue versus red, it may give us an incomplete picture. The amounts of green and magenta which LEDs and fluorescents emit varies too, and some parts of the spectrum might be missing altogether, but that’s a whole other can of worms.
The human eye-brain system ignores most differences of colour temperature in daily life, accepting all but the most extreme examples as white light. In professional cinematography, we choose a white balance either to render colours as our eyes perceive them or for creative effect.
Most cameras today have a number of white balance presets, such as tungsten, sunny day and cloudy day, and the options to dial in a numerical colour temperature directly or to tell the camera that what it’s currently looking at (typically a white sheet of paper) is indeed white. These work by applying or reducing gain to the red or blue channels of the electronic image.
Interestingly, this means that all cameras have a “native” white balance, a white balance setting at which the least total gain is applied to the colour channels. Arri quotes 5,600K for the Alexa, and indeed the silicon in all digital sensors is inherently less sensitive to blue light than red, making large amounts of blue gain necessary under tungsten lighting. In an extreme scenario – shooting dark, saturated blues in tungsten mode, for example – this might result in objectionable picture noise, but the vast majority of the time it isn’t an issue.
The difficulty with white balance is mixed lighting. A typical example is a person standing in a room with a window on one side of them and a tungsten lamp on the other. Set your camera’s white balance to daylight (perhaps 5,600K) and the window side of their face looks correct, but the other side looks orange. Change the white balance to tungsten (3,200K) and you will correct that side of the subject’s face, but the daylight side will now look blue.
Throughout much of the history of colour cinematography, this sort of thing was considered to be an error. To correct it, you would add CTB (colour temperature blue) gel to the tungsten lamp or perhaps even place CTO (colour temperature orange) gel over the window. Nowadays, of course, we have bi-colour and RGB LED fixtures whose colour temperature can be instantly changed, but more importantly there has been a shift in taste. We’re no longer tied to making all light look white.
To give just one example, Suzie Lavelle, award-winning DP of Normal People, almost always shoots at 4,300K, halfway between typical tungsten and daylight temperatures. She allows her practical lamps to look warm and cozy, while daylight sources come out as a contrasting blue.
It is important to understand colour temperature as a DP, so that you can plan your lighting set-ups and know what colours will be obtained from different sources. However, the choice of white balance is ultimately a creative one, perhaps made at the monitor, dialling through the kelvins to see what you like, or even changed completely in post-production.
White walls are the bane of a DP’s existence. They bounce light around everywhere, killing the mood, and they look cheap and boring in the background of your shot. Nonetheless, with so many contemporary buildings decorated this way, it’s a challenge we all have to face. Today I’m going to look back on two short films I’ve photographed, and explain the different approaches I took to get the white-walled locations looking nice.
Finding Hope is a moving drama about a couple grieving for the baby they have lost. It was shot largely at the home of the producer, Jean Maye, on a Sony FS7 with Sigma and Pentax stills glass.
Exit Eve is a non-linear narrative about the dehumanisation of an au pair by her wealthy employers. With a fairly respectable budget for a short, this production shot in a luxurious Battersea townhouse on an Arri Alexa Classic with Ultra Primes.
“Crown”-inspired colour contrast
It was January 2017 when we made Finding Hope, and I’d recently been watching a lot of The Crown. I liked how that series punctuated its daylight interior frames with pools of orange light from practicals. We couldn’t afford much of a lighting package, and I thought that pairing existing pracs with dimmers and tungsten bulbs would be a cheap and easy way to break up the white walls and bring some warmth – perhaps a visual representation of the titular hope – into the heavy story.
I shot all the daylight interiors at 5600K to get that warmth out of the pracs. Meanwhile I shaped the natural light as far as possible with the existing curtains, and beefed it up with a 1.2K HMI where I could. I used no haze or lens diffusion on the film because I felt it needed the unforgiving edges.
For close-ups, I often cheated the pracs a little closer and tweaked the angle, but I chose not to supplement them with movie lamps. The FS7’s native ISO of 2500 helped a lot, especially in a nighttime scene where the grieving parents finally let each other in. Director Krysten Resnick had decided that there would be tea-lights on the kitchen counter, and I asked art director Justine Arbuthnot to increase the number as much as she dared. They became the key-light, and again I tweaked them around for the close-ups.
My favourite scene in Finding Hope is another nighttime one, in which Crystal Leaity sits at a piano while Kevin Leslie watches from the doorway. I continued the theme of warm practicals, bouncing a bare 100W globe off the wall as Crystal’s key, and shaping the existing hall light with some black wrap, but I alternated that with layers of contrasting blue light: the HMI’s “moonlight” coming in through the window, and the flicker of a TV in the deep background. This latter was a blue-gelled 800W tungsten lamp bounced off a wobbling reflector.
When I saw the finished film, I was very pleased that the colourist had leant into the warm/cool contrast throughout the piece, even teasing it out of the daylight exteriors.
Trapped in a stark white townhouse
I took a different approach to colour in Exit Eve. Director Charlie Parham already knew that he wanted strong red lighting in party scenes, and I felt that this would be most effective if I kept colour out of the lighting elsewhere. As the film approaches its climax, I did start to bring in the orange of outside streetlamps, and glimpses of the party’s red, but otherwise I kept the light stark and white.
Converted from a Victorian schoolhouse, the location had high ceilings, huge windows and multiple floors, so I knew that I would mostly have to live with whatever natural light did or didn’t shine in. We were shooting during the heatwave of 2018, with many long handheld takes following lead actor Thalissa Teixeria from room to room and floor to floor, so even the Alexa’s dynamic range struggled to cope with the variations in light level.
For a night scene in the top floor bedroom, I found that the existing practicals were perfectly placed to provide shape and backlight. I white-balanced to 3600K to keep most of the colour out of them, and rigged black solids behind the camera to prevent the white walls from filling in the shadows.
(Incidentally, the night portions of this sequence were shot as one continuous take, despite comprising two different scenes set months apart. The actors did a quick-change and the bed was redressed by the art department while it was out frame, but sadly this tour de force was chopped up in the final cut.)
I had most control over the lighting when it came to the denouement in the ground floor living area. Here I was inspired by the work of Bradford Young, ASC to backlight the closed blinds (with tungsten units gelled to represent streetlights) and allow the actors inside to go a bit dim and murky. For a key moment we put a red gel on one of the existing spotlights in the living room and let the cast step into it.
So there we have it, two different approaches to lighting in a while-walled location: creating colour contrast with dimmed practicals, or embracing the starkness and saving the colour for dramatic moments. How will you tackle your next magnolia-hued background?
For another example of how I’ve tackled white-walled locations, see my Forever Alone blog.
So far, this blog series about my cinematography of The Little Mermaid has covered the biggest and most complex scenes in the movie. Today I’m going to look at some smaller scenes, and how I employed the cinematography tenet of lighting from the back to quickly build a look for these which has depth, mood and drama.
Many of these examples are specifically cross-backlighting, something I covered in my Lighting Techniques series, but I’ll quickly recap since it has so much relevance here. It involves lighting two characters facing each other with two sources, on the far side of the eye-line (short key), crossed so that each source keys one character and often backlights the other too.
So with that in mind, let’s proceed to the examples from my shooting diary.
The first week is pretty much all in houses with just a few principals, so an easy start. Day 1’s schedule is tight though. We start in a third floor bedroom – no way lamps are getting up to those windows from outside, so I’m relying on natural light augmented with a bit of cross-backlight cheated inside the room. (There’s a Kino Flo shining at Elle over Cam’s right shoulder, for example.) Once the haze is in it looks great. After we get the main coverage, we head out to the garden for the next scene, while the ‘B’ camera team steps in to pick up a couple of inserts…
…It’s a night scene and the grips have tented the window. To get a nice blue glow coming in, I have two 4×4 Kino Flos set either side of the window (outside), and they give a great wrapping backlight to the actors and the set dressing. Smoke and a cool white balance of 3,200K (the Kinos are tubed for 5,600K) complete the look. It owes a lot to a scene from Hook, one of Blake’s (director Blake Harris) reference movies which I watched during preprod. This stuff definitely filters in and inspires things!
Our first day on stage. It’s weird to be back at the former supermarket I spent five weeks of preproduction in. The first set, Locke’s chamber, is very confined and the walls don’t wild, so it’s quite slow-going to work in there. We fire a 5K fresnel through the stained glass window at the back of the set. Then I fall back on the tried and tested method of cross-backlighting even though I know that it will be hard to hide the lamps (a 650W fresnel in both of the upper rear corners of the set) from camera. In the end I have the art department dress drapes in front of them. For the villain’s single I leave the light hard, but for the hero’s single we use bounce boards to wrap the light around his face more…
We start with the fortune-teller’s tent, another small set constructed on stage. In fact, it’s just an Easy-Up artfully draped with fabrics. Initially there’s nowhere to get light in from except the front, but I know that this will leave the scene looking flat and fake, so I work with the art department again to make holes in the top rear corners. Through those we shine tungsten-bubbled “Fat Boy” Kino Flos. (These 2ft 4-bank units are giving the dual kickers on Cam in the centre, and the beautiful down-light on the background fabrics, bringing out the ruching. Each one also provides a little key-light on the two ladies.) The other sources are “moonlight” coming in through the entrance, linking us to the circus exteriors, and a stylised slash of light across Thora’s eyes from a Source Four, suggested by Jason (key grip Jason Batey). Adding foreground practicals is an important final touch to expand the depth and scale of the set…
It’s the last day of principal photography. Our big scene of the day is the newspaper office where Cam works, which is a set in the front of the studio, using the building’s real windows. We fire the 12K in and gel it with half CTS for a nice morning sunlight effect. We’re shooting towards the windows, which have blinds, so we get some nice shafts of light, though sometimes it’s a little too smokey. Running haze is a pretty skilled and tricky job, and involves considering the lens length and backlight, which both affect how much the smoke shows up on camera. When we get it right, combined with the dark wood period furniture, it totally sells the 1937 setting. Apparently people at video village are loving it, saying it looks like Mad Men….
Although The Little Mermaid takes place mostly on dry land, there were some key scenes involving tanks and pools. These include the moment which introduces the audience to the mermaid herself, played by Poppy Drayton. Here are some extracts from my diary covering the challenges of creating a magical, fairytale look while filming in and around water.
Today we’re inside the big top all day – actually all NIGHT. We can’t shoot during the day because too much daylight bleeds through the canvas of the tent.
We are setting up when a storm hits. The tent starts to blow about in a slightly alarming fashion, rain lashes down outside (and inside, because the tent isn’t very waterproof) and lightning flashes. We are ordered out of the tent, and I run into a waiting mini-van with Joe from art and some of the camera crew. We sit watching the rain and telling stories for half an hour before we can press on.
Around the wall of the tent the art department have hung canvas posters; at the suggestion of gaffer Mike Horton, we uplight these with par cans and par 38s. The design of these fixtures hasn’t changed since the 30s, so we can get away with seeing them in shot. The art dept have sourced four period spotlights which we use as background interest (they’re not powerful enough to really illuminate anything), as well as string-lights.
Ambience comes from a Maxi Brute, with just a couple of bubbles on, firing into the tent roof. After seeing a video test of various diffusersduring preproduction, I asked for Moroccan Frost to be added to our consumables list, and we use it for the first time on this Maxi Brute. It gives a lovely muted orangey-pink look to the scene.
We’re shooting our mermaid for the very first time, in a tank in the circus ring. The initial plan is to fire a Source Four straight down into the water to create genuine watery rippling light, while bouncing a par can off a wobbling frame of blue gel to beef up the effect. In the end the Source Four isn’t really cutting it, so instead we rig a 575W HMI, gelled with Steel Blue, to a menace arm and fire it into the tank as toppy backlight. This Steel Blue gelled daylight source, blued up slightly further by the water itself, contrasts beautifully with the Moroccan Frost tungsten ambience which the Maxi Brutes are giving us.
In her mermaid tail and costume, Poppy Drayton looks stunning in the tank. We shoot steadicam angles and some slo-mo to get the most out of the set-up.
Back on stage, and we’re shooting the rocky pool. This set was built before I even arrived in Savannah, so I’ve been waiting a long time to shoot it. It’s built almost right up to the ceiling of the studio (a former supermarket) so it’s challenging to light. The grips build four menace arms and poke two 4×4 Kinos and two 575W HMIs over the sides to cross-light the set and bring out all the texture in it. Where the set ends they put up a 20×20′ greenscreen, which we light with two Kino Flo Image 80s fitted with special chroma green tubes.
After a wide (which didn’t make the final cut), the next set-up is a 2-shot of our leads in the pool itself. We consider arming the camera out over the pool using a jib, but ultimately decide that it’s better for me to join the cast in the pool, with the camera on my shoulder in a splash bag. 2nd AC Kane Pearson joins the pool party as well, and ends up hand-bashing a monitor for me since the splash bag’s designed for a Panaflex film camera and the viewfinder doesn’t line up. I’m reminded of my frustrating splash bag experience on See Saw back in 2007, but this time at least within a few minutes I’ve found a comfortable and effective way to operate the camera, under-slinging it and allowing it to partially float so I don’t have to support the whole weight.
For this shot we’ve added our par-can-bounced-off-a-wobbling-blue-gel gag for watery light ripples, and combined with the real light ripples and the reflections of a 1.2K HMI backlight, the image looks beautiful.
After lunch we shoot the singles for the rocky pool scene. The pool itself has been removed, and the actors sit on stools in a paddling pool, with the set behind them. The paddling pool serves two functions: it catches the water that make-up pours over the actors to make them look wet, and it reflects rippling light onto their faces. This light originates from a par can. At first it flattens out the look, then we figure out that we need to lay black fabric on the bottom of the pool. This stops the par can’s light bouncing directly, while retaining the rippling highlights off the water’s surface. (Check out my article on shooting water for more tips like this.)
In the final edit this was all intercut with some beautiful footage by underwater DP Jordan Klein, shot both at a local diving pool in Savannah and at Weeki Wachee Springs State Park in Florida. The main unit shot another scene in the actual ocean, but I’ll cover that later in this series. In the meantime, next week I’ll reveal some of the tricks and techniques used in shooting The Little Mermaid‘s many sequences in moving vehicles.
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.
Last week I looked at the science of colour: what it is, how our eyes see it, and how cameras see and process it. Now I’m going to look at colour theory – that is, schemes of mixing colours to produce aesthetically pleasing results.
The Colour wheel
The first colour wheel was drawn by Sir Isaac Newton in 1704, and it’s a precursor of the CIE diagram we met last week. It’s a method of arranging hues so that useful relationships between them – like primaries and secondaries, and the schemes we’ll cover below – can be understood. As we know from last week, colour is in reality a linear spectrum which we humans perceive by deducing it from the amounts of light triggering our red, green and blue cones, but certain quirks of our visual system make a wheel in many ways a more useful arrangement of the colours than a linear spectrum.
One of these quirks is that our long (red) cones, although having peak sensitivity to red light, have a smaller peak in sensitivity at the opposite (violet) end of the spectrum. This may be what causes our perception of colour to “wrap around”.
Another quirk is in the way that colour information is encoded in the retina before being piped along the optic nerve to the brain. Rather than producing red, green and blue signals, the retina compares the levels of red to green, and of blue to yellow (the sum of red and green cones), and sends these colour opponency channels along with a luminance channel to the brain.
You can test these opposites yourself by staring at a solid block of one of the colours for around 30 seconds and then looking at something white. The white will initially take on the opposing colour, so if you stared at red then you will see green.
19th century physiologist Ewald Hering was the first to theorise about this colour opponency, and he designed his own colour wheel to match it, having red/green on the vertical axis and blue/yellow on the horizontal.
Today we are more familiar with the RGB colour wheel, which spaces red, green and blue equally around the circle. But both wheels – the first dealing with colour perception in the eye-brain system, and the second dealing with colour representation on an RGB screen – are relevant to cinematography.
On both wheels, colours directly opposite each other are considered to cancel each other out. (In RGB they make white when combined.) These pairs are known as complementary colours.
A complementary scheme provides maximum colour contrast, each of the two hues making the other more vibrant. Take “The Snail” by modernist French artist Henri Matisse, which you can currently see at the Tate Modern; Matisse placed complementary colours next to each other to make them all pop.
In cinematography, a single pair of complementary colours is often used, for example the yellows and blues of Aliens‘ power loader scene:
Or this scene from Life on Mars which I covered on my YouTube show Lighting I Like:
I frequently use a blue/orange colour scheme, because it’s the natural result of mixing tungsten with cool daylight or “moonlight”.
And then of course there’s the orange-and-teal grading so common in Hollywood:
Amélie uses a less common complementary pairing of red and green:
An analogous colour scheme uses hues adjacent to each other on the wheel. It lacks the punch and vibrancy of a complementary scheme, instead having a harmonious, unifying effect. In the examples below it seems to enhance the single-mindedness of the characters. Sometimes filmmakers push analogous colours to the extreme of using literally just one hue, at which point it is technically monochrome.
There are other colour schemes, such as triadic, but complementary and analogous colours are by far the most common in cinematography. In a future post I’ll look at the psychological effects of individual colours and how they can be used to enhance the themes and emotions of a film.
Colour is a powerful thing. It can identify a brand, imply eco-friendliness, gender a toy, raise our blood pressure, calm us down. But what exactly is colour? How and why do we see it? And how do cameras record it? Let’s find out.
The Meaning of “Light”
One of the many weird and wonderful phenomena of our universe is the electromagnetic wave, an electric and magnetic oscillation which travels at 186,000 miles per second. Like all waves, EM radiation has the inversely-proportional properties of wavelength and frequency, and we humans have devised different names for it based on these properties.
EM waves with a low frequency and therefore a long wavelength are known as radio waves or, slightly higher in frequency, microwaves; we used them to broadcast information and heat ready-meals. EM waves with a high frequency and a short wavelength are known as x-rays and gamma rays; we use them to see inside people and treat cancer.
In the middle of the electromagnetic spectrum, sandwiched between infrared and ultraviolet, is a range of frequencies between 430 and 750 terahertz (wavelengths 400-700 nanometres). We call these frequencies “light”, and they are the frequencies which the receptors in our eyes can detect.
If your retinae were instead sensitive to electromagnetic radiation of between 88 and 91 megahertz, you would be able to see BBC Radio 2. I’m not talking about magically seeing into Ken Bruce’s studio, but perceiving the FM radio waves which are encoded with his silky-smooth Scottish brogue. Since radio waves can pass through solid objects though, perceiving them would not help you to understand your environment much, whereas light waves are absorbed or reflected by most solid objects, and pass through most non-solid objects, making them perfect for building a picture of the world around you.
Within the range of human vision, we have subdivided and named smaller ranges of frequencies. For example, we describe light of about 590-620nm as “orange”, and below about 450nm as “violet”. This is all colour really is: a small range of wavelengths (or frequencies) of electromagnetic radiation, or a combination of them.
In the eye of the beholder
The inside rear surfaces of your eyeballs are coated with light-sensitive cells called rods and cones, named for their shapes.
The human eye has about five or six million cones. They come in three types: short, medium and long, referring to the wavelengths to which they are sensitive. Short cones have peak sensitivity at about 420nm, medium at 530nm and long at 560nm, roughly what we call blue, green and red respectively. The ratios of the three cone types vary from person to person, but short (blue) ones are always in the minority.
Rods are far more numerous – about 90 million per eye – and around a hundred times more sensitive than cones. (You can think of your eyes as having dual native ISOs like a Panasonic Varicam, with your rods having an ISO six or seven stops faster than your cones.) The trade-off is that they are less temporally and spatially accurate than cones, making it harder to see detail and fast movement with rods. However, rods only really come into play in dark conditions. Because there is just one type of rod, we cannot distinguish colours in low light, and because rods are most sensitive to wavelengths of 500nm, cyan shades appear brightest. That’s why cinematographers have been painting night scenes with everything from steel grey to candy blue light since the advent of colour film.
The three types of cone are what allow us – in well-lit conditions – to havecolour vision. This trichromatic vision is not universal, however. Many animals have tetrachromatic (four channel) vision, and research has discovered some rare humans with it too. On the other hand, some animals, and “colour-blind” humans, are dichromats, having only two types of cone in their retinae. But in most people, perceptions of colour result from combinations of red, green and blue. A combination of red and blue light, for example, appears as magenta. All three of the primaries together make white.
Compared with the hair cells in the cochlea of your ears, which are capable of sensing a continuous spectrum of audio frequencies, trichromacy is quite a crude system, and it can be fooled. If your red and green cones are triggered equally, for example, you have no way of telling whether you are seeing a combination of red and green light, or pure yellow light, which falls between red and green in the spectrum. Both will appear yellow to you, but only one really is. That’s like being unable to hear the difference between, say, the note D and a combination of the notes C and E. (For more info on these colour metamers and how they can cause problems with certain types of lighting, check out Phil Rhode’s excellent article on Red Shark News.)
Mimicking your eyes, video sensors also use a trichromatic system. This is convenient because it means that although a camera and TV can’t record or display yellow, for example, they can produce a mix of red and green which, as we’ve just established, is indistinguishable from yellow to the human eye.
Rather than using three different types of receptor, each sensitive to different frequencies of light, electronic sensors all rely on separating different wavelengths of light before they hit the receptors. The most common method is a colour filter array (CFA) placed immediately over the photosites, and the most common type of CFA is the Bayer filter, patented in 1976 by an Eastman Kodak employee named Dr Bryce Bayer.
The Bayer filter is a colour mosaic which allows only green light through to 50% of the photosites, only red light through to 25%, and only blue to the remaining 25%. The logic is that green is the colour your eyes are most sensitive to overall, and that your vision is much more dependent on luminance than chrominance.
The resulting image must be debayered (or more generally, demosaiced) by an algorithm to produce a viewable image. If you’re recording log or linear then this happens in-camera, whereas if you’re shooting RAW it must be done in post.
This system has implications for resolution. Let’s say your sensor is 2880×1620. You might think that’s the number of pixels, but strictly speaking it isn’t. It’s the number of photosites, and due to the Bayer filter no single one of those photosites has more than a third of the necessary colour information to form a pixel of the final image. Calculating that final image – by debayering the RAW data – reduces the real resolution of the image by 20-33%. That’s why cameras like the Arri Alexa or the Blackmagic Cinema Camera shoot at 2.8K or 2.5K, because once it’s debayered you’re left with an image of 2K (cinema standard) resolution.
Your optic nerve can only transmit about one percent of the information captured by the retina, so a huge amount of data compression is carried out within the eye. Similarly, video data from an electronic sensor is usually compressed, be it within the camera or afterwards. Luminance information is often prioritised over chrominance during compression.
You have probably come across chroma subsampling expressed as, for example, 444 or 422, as in ProRes 4444 (the final 4 being transparency information, only relevant to files generated in postproduction) and ProRes 422. The three digits describe the ratios of colour and luminance information: a file with 444 chroma subsampling has no colour compression; a 422 file retains colour information only in every second pixel; a 420 file, such as those on a DVD or BluRay, contains one pixel of blue info and one of red info (the green being derived from those two and the luminance) to every four pixels of luma.
Whether every pixel, or only a fraction of them, has colour information, the precision of that colour info can vary. This is known as bit depth or colour depth. The more bits allocated to describing the colour of each pixel (or group of pixels), the more precise the colours of the image will be. DSLRs typically record video in 24-bit colour, more commonly described as 8bpc or 8 bits per (colour) channel. Images of this bit depth fall apart pretty quickly when you try to grade them. Professional cinema cameras record 10 or 12 bits per channel, which is much more flexible in postproduction.
The third attribute of recorded colour is gamut, the breadth of the spectrum of colours. You may have seen a CIE (Commission Internationale de l’Eclairage) diagram, which depicts the range of colours perceptible by human vision. Triangles are often superimposed on this diagram to illustrate the gamut (range of colours) that can be described by various colour spaces. The three colour spaces you are most likely to come across are, in ascending order of gamut size: Rec.709, an old standard that is still used by many monitors; P3, used by digital cinema projectors; and Rec.2020. The latter is the standard for ultra-HD, and Netflix are already requiring that some of their shows are delivered in it, even though monitors capable of displaying Rec.2020 do not yet exist. Most cinema cameras today can record images in Rec.709 (known as “video” mode on Blackmagic cameras) or a proprietary wide gamut (“film” mode on a Blackmagic, or “log” on others) which allows more flexibility in the grading suite. Note that the two modes also alter the recording of luminance and dynamic range.
To summarise as simply as possible: chroma subsampling is the proportion of pixels which have colour information, bit depth is the accuracy of that information and gamut is the limits of that info.
That’s all for today. In future posts I will look at how some of the above science leads to colour theory and how cinematographers can make practical use of it.
Having lately shot my first roll of black-and-white film in a decade, I thought now would be a good time to delve into the story of monochrome image-making and the various reasons artists have eschewed colour.
I found the recent National Gallery exhibition, Monochrome: Painting in Black and White, a great primer on the history of the unhued image. Beginning with examples from medieval religious art, the exhibition took in grisaille works of the Renaissance before demonstrating the battle between painting and early photography, and finishing with monochrome modern art.
Several of the pictures on display were studies or sketches which were generated in preparation for colour paintings. Ignoring hue allowed the artists to focus on form and composition, and this is still one of black-and-white’s great strengths today: stripping away chroma to heighten other pictorial effects.
What fascinated me most in the exhibition were the medieval religious paintings in the first room. Here, old testament scenes in black-and-white were painted around a larger, colour scene from the new testament; as in the modern TV trope, the flashbacks were in black-and-white. In other pictures, a colour scene was framed by a monochrome rendering of stonework – often incredibly realistic – designed to fool the viewer into thinking they were seeing a painting in an architectural nook.
During cinema’s long transition from black-and-white to colour, filmmakers also used the two modes to define different layers of reality. When colour processes were still in their infancy and very expensive, filmmakers selected particular scenes to pick out in rainbow hues, while the surrounding material remained in black-and-white like the borders of the medieval paintings. By 1939 the borders were shrinking, as The Wizard of Oz portrayed Kansas, the ordinary world, in black-and-white, while rendering Oz – the bulk of the running time – in colour.
Michael Powell, Emeric Pressburger and legendary Technicolor cinematographer Jack Cardiff, OBE, BSC subverted expectations with their 1946 fantasy-romance A Matter of Life and Death, set partly on Earth and partly in heaven. Says Cardiff in his autobiography:
Quite early on I had said casually to Michael Powell, “Of course heaven will be in colour, won’t it?” And Michael replied, “No. Heaven will be in black and white.” He could see I was startled, and grinned: “Because everyone will expect heaven to be in colour, I’m doing it in black-and-white.”
Ironically Cardiff had never shot in black-and-white before, and he ultimately captured the heavenly scenes on three-strip Technicolor, but didn’t have the colour fully developed, resulting in a pearlescent monochrome.
Meanwhile, DPs like John Alton, ASC were pushing greyscale cinematography to its apogee with a genre that would come to be known as film noir. Oppressed Jews like Alton fled the rising Nazism of Europe for the US, bringing German Expressionism with them. The result was a trend of hardboiled thrillers lit with oppressive contrast, harsh shadows, concealing silhouettes and dramatic angles, all of which were heightened by the lack of distracting colour.
Alton himself had a paradoxical relationship with chroma, famously stating that “black and white are colours”. While he is best known today for his noir, his only Oscar win was for his work on the Technicolor musical An American in Paris, the designers of which hated Alton for the brightly-coloured light he tried to splash over their sets and costumes.
It wasn’t just Alton that was moving to colour. Soon the economics were clear: chromatic cinema was more marketable and no longer prohibitively expensive. The writing was on the wall for black-and-white movies, and by the end of the sixties they were all but gone.
I was brought up in a world of default colour, and the first time I can remember becoming aware of black-and-white was when Schindler’s List was released in 1993. I can clearly recall a friend’s mother refusing to see the film because she felt she wouldn’t be getting her money’s worth if there was no colour. She’s not alone in this view, and that’s why producers are never keen to green-light monochrome movies. Spielberg only got away with it because his name was proven box office gold.
A few years later, Jonathan Frakes and his DP Matthew F. Leonetti, ASC wanted to shoot the holodeck sequence of Star Trek: First Contact in black-and-white, but the studio deemed test footage “too experimental”. For the most part, the same attitude prevails today. Despite being marketed as a “visionary” director ever since Pan’s Labyrinth, Guillermo del Toro’s vision of The Shape of Water as a black-and-white film was rejected by financiers. He only got the multi-Oscar-winning fairytale off the ground by reluctantly agreeing to shoot in colour.
Yet there is reason to be hopeful about black-and-white remaining an option for filmmakers. In 2007 MGM denied Frank Darabont the chance to make The Mist in black-and-white, but they permitted a desaturated version on the DVD. Darabont had this to say:
No, it doesn’t look real. Film itself [is a] heightened recreation of reality. To me, black-and-white takes that one step further. It gives you a view of the world that doesn’t really exist in reality and the only place you can see that representation of the world is in a black-and-white movie.
In 2016, a “black and chrome” version of Mad Max: Fury Road was released on DVD and Blu-Ray, with director George Miller saying:
The best version of “Road Warrior” [“Mad Max 2”] was what we called a “slash dupe,” a cheap, black-and-white version of the movie for the composer. Something about it seemed more authentic and elemental. So I asked Eric Whipp, the [“Fury Road”] colourist, “Can I see some scenes in black-and-white with quite a bit of contrast?” They looked great. So I said to the guys at Warners, “Can we put a black-and-white version on the DVD?”
The following year, Logan director James Mangold’s black-and-white on-set photos proved so popular with the public that he decided to create a monochrome version of the movie. “The western and noir vibes of the film seemed to shine in the form, and there was not a trace of the modern comic hero movie sheen,” he said. Most significantly, the studio approved a limited theatrical release for Logan Noir, presumably seeing the extra dollar-signs of a second release, rather than the reduced dollar-signs of a greyscale picture.
Perhaps the medium of black-and-white imaging has come full circle. During the Renaissance, greyscale images were preparatory sketches, stepping stones to finished products in colour. Today, the work-in-progress slash dupe of Road Warrior and James Mangold’s photographic studies of Logan were also stepping stones to colour products, while at the same time closing the loop by inspiring black-and-white products too.
With the era of budget- and technology-mandated monochrome outside the living memory of many viewers today, I think there is a new willingness to accept black-and-white as an artistic choice. The acclaimed sci-fi anthology series Black Mirror released an episode in greyscale this year, and where Netflix goes, others are bound to follow.
After fourteen nominations, celebrated cinematographer Roger Deakins, CBE, BSC, ASC finally won an Oscar last night, for his work on Denis Villeneuve’s Blade Runner 2049. Villeneuve’s sequel to Ridley Scott’s 1982 sci-fi noir is not a perfect film; its measured, thoughtful pace is not to everyone’s taste, and it has serious issues with women – all of the female characters being highly sexualised, callously slaughtered, or both – but the Best Cinematography Oscar was undoubtedly well deserved. Let’s take a look at the photographic style Deakins employed, and how it plays into the movie’s themes.
Blade Runner 2049 returns to the dystopian metropolis of Ridley Scott’s classic three decades later, introducing us to Ryan Gosling’s K. Like Harrison Ford’s Deckard before him, K is a titular Blade Runner, tasked with locating and “retiring” rogue replicants – artificial, bio-engineered people. He soon makes a discovery which could have huge implications both for himself and the already-strained relationship between humans and replicants. In his quest to uncover the truth, K must track down Deckard for some answers.
Villeneuve’s film meditates on deep questions of identity, creating a world in which you can never be sure who is or isn’t real – or even what truly constitutes being “real”. Deakins reinforces this existential uncertainty by reducing characters and locations to mere forms. Many scenes are shrouded in smog, mist, rain or snow, rendering humans and replicants alike as silhouettes.
K spends his first major scene seated in front of a window, the side-light bouncing off a nearby cabinet the only illumination on his face. Deakins’ greatest strength is his ability to adapt to whatever style each film requires, but if he has a recognisable signature it’s this courage to rely on a single source and let the rest of the frame go black.
Whereas Scott and his DP Jordan Cronenweth portrayed LA mainly at night, ablaze with pinpoints of light, Villeneuve and Deakins introduce it in daylight, but a daylight so dim and smog-ridden that it reveals even less than those night scenes from 1982.
All this is not to say that the film is frustratingly dark, or that audiences will struggle to make out what is going on. Shooting crisply on Arri Alexas with Arri/Zeiss Master Primes, Deakins is a master of ensuring that you see what you need to see.
A number of the film’s sequences are colour-coded, delineating them as separate worlds. The city is mainly fluorescent blues and greens, visually reinforcing the sickly state of society, with the police department – an attempt at justice in an insane world – a neutral white.
The Brutalist headquarters of Jared Leto’s blind entrepreneur Wallace are rendered in gold, as though the corporation attempted a friendly yellow but was corrupted by greed. These scenes also employ rippling reflections from pools of water. Whereas the watery light in the Tyrell HQ of Scott’s Blade Runner was a random last-minute idea by the director, concerned that his scene lacked enough interest and production value, here the light is clearly motivated by architectural water features. Yet it is used symbolically too, and very effectively so, as it underscores one of Blade Runner 2049’s most powerful scenes. At a point in the story where more than one character is calling their memories into question, the ripples playing across the walls are as intangible and illusory as those recollections. “I know what’s real,” Deckard asserts to Wallace, but both the photography and Ford’s performance bely his words.
The most striking use of colour is the sequence in which K first tracks Deckard down, hiding out in a Las Vegas that’s been abandoned since the detonation of a dirty bomb. Inspired by photos of the Australian dust storm of 2009, Deakins bathed this lengthy sequence in soft, orangey-red – almost Martian – light. This permeating warmth, contrasting with the cold artificial light of LA, underlines the personal nature of K’s journey and the theme of birth which is threaded throughout the film.
Deakins has stated in interviews that he made no attempt to emulate Cronenweth’s style of lighting, but nonetheless this sequel feels well-matched to the original in many respects. This has a lot to do with the traditional camerawork, with most scenes covered in beautifully composed static shots, and movement accomplished where necessary with track and dolly.
The visual effects, which bagged the film’s second Oscar, also drew on techniques of the past; the above featurette shows a Canon 1DC tracking through a miniature landscape at 2:29. “Denis and I wanted to do as much as possible in-camera,” Deakins told Variety, “and we insisted when we had the actors, at least, all the foreground and mid-ground would be in-camera.” Giant LED screens were used to get authentic interactive lighting from the advertising holograms on the city streets.
One way in which the lighting of the two Blade Runner movies is undeniably similar is the use of moving light sources to suggest an exciting world continuing off camera. (The infamous lens flares of J.J. Abrahms’ Star Trek served the same purpose, illustrating Blade Runner’s powerful influence on the science fiction genre.) But whereas, in the original film, the roving searchlights pierce the locations sporadically and intrusively, the dynamic lights of Blade Runner 2049 continually remodel the actors’ faces. One moment a character is in mysterious backlight, the next in sinister side-light, and the next in revealing front-light – inviting the audience to reassess who these characters are at every turn.
This obfuscation and transience of identity and motivation permeates the whole film, and is its core visual theme. The 1982 Blade Runner was a deliberate melding of sci-fi and film noir, but to me the sequel does not feel like noir at all. Here there is little hard illumination, no binary division of light and dark. Instead there is insidious soft light, caressing the edge of a face here, throwing a silhouette there, painting everyone on a continuous (and continuously shifting) spectrum between reality and artificiality.
Blade Runner 2049 is a much deeper and more subtle film than its predecessor, and Deakins’ cinematography beautifully reflects this.
Recently work began on colour grading Above the Clouds, a comedy road movie I shot for director Leon Chambers. I’ve covered every day of shooting here on my blog, but the story wouldn’t be complete without an account of this crucial stage of postproduction.
I must confess I didn’t give much thought to the grade during the shoot, monitoring in Rec.709 and not envisaging any particular “look”. So when Leon asked if I had any thoughts or references to pass on to colourist Duncan Russell, I had to put my thinking cap on. I came up with a few different ideas and met with Leon to discuss them. The one that clicked with his own thoughts was a super-saturated vintage postcard (above). He also liked how, in a frame grab I’d been playing about with, I had warmed up the yellow of the car – an important character in the movie!
Leon was keen to position Above the Clouds‘ visual tone somewhere between the grim reality of a typical British drama and the high-key gloss of Hollywood comedies. Finding exactly the right spot on that wide spectrum was the challenge!
“Real but beautiful” was Duncan’s mantra when Leon and I sat down with him last week for a session in Freefolk’s Baselight One suite. He pointed to the John Lewis “Tiny Dancer” ad as a good touchstone for this approach.
We spent the day looking at the film’s key sequences. There was a shot of Charlie, Oz and the Yellow Peril (the car) outside the garage from week one which Duncan used to establish a look for the three characters. It’s commonplace nowadays to track faces and apply individual grades to them, making it possible to fine-tune skin-tones with digital precision. I’m pleased that Duncan embraced the existing contrast between Charlie’s pale, freckled innocence and Oz’s dirty, craggy world-weariness.
Above the Clouds was mainly shot on an Alexa Mini, in Log C ProRes 4444, so there was plenty of detail captured beyond the Rec.709 image that I was (mostly) monitoring. A simple example of this coming in useful is the torchlight charity shop scene, shot at the end of week two. At one point Leo reaches for something on a shelf and his arm moves right in front of his torch. Power-windowing Leo’s arm, Duncan was able to bring back the highlight detail, because it had all been captured in the Log C.
But just because all the detail is there, it doesn’t mean you can always use it. Take the gallery scenes, also shot in week two, at the Turner Contemporary in Margate. The location has large sea-view windows and white walls. Many of the key shots featured Oz and Charlie with their backs towards the windows. This is a classic contrasty situation, but I knew from checking the false colours in log mode that all the detail was being captured.
Duncan initially tried to retain all the exterior detail in the grade, by separating the highlights from the mid-tones and treating them differently. He succeeded, but it didn’t look real. It looked like Oz and Charlie were green-screened over a separate background. Our subconscious minds know that a daylight exterior cannot be only slightly brighter than an interior, so it appeared artificial. It was necessary to back off on the sky detail to keep it feeling real. (Had we been grading in HDR [High Dynamic Range], which may one day be the norm, we could theoretically have retained all the detail while still keeping it realistic. However, if what I’ve heard of HDR is correct, it may have been unpleasant for audiences to look at Charlie and Oz against the bright light of the window beyond.)
There were other technical challenges to deal with in the film as well. One was the infra-red problem we encountered with our ND filters during last autumn’s pick-ups, which meant that Duncan had to key out Oz’s apparently pink jacket and restore it to blue. Another was the mix of formats employed for the various pick-ups: in addition to the Alexa Mini, there was footage from an Arri Amira, a Blackmagic Micro Cinema Camera (BMMCC) and even a Canon 5D Mk III. Although the latter had an intentionally different look, the other three had to match as closely as possible.
A twilight scene set in a rural village contains perhaps the most disparate elements. Many shots were done day-for-dusk on the Alexa Mini in Scotland, at the end of week four. Additional angles were captured on the BMMCC in Kent a few months later, both day-for-dusk and dusk-for-dusk. This outdoor material continues directly into indoor scenes, shot on a set this February on the Amira. Having said all that, they didn’t match too badly at all, but some juggling was required to find a level of darkness that worked for the whole sequence while retaining consistency.
In other sequences, like the ones in Margate near the start of the film, a big continuity issue is the clouds. Given the film’s title, I always tried to frame in plenty of sky and retain detail in it, using graduated ND filters where necessary. Duncan was able to bring out, suppress or manipulate detail as needed, to maintain continuity with adjacent shots.
Consistency is important in a big-picture sense too. One of the last scenes we looked at was the interior of Leo’s house, from weeks two and three, for which Duncan hit upon a nice, painterly grade with a bit of mystery to it. The question is, does that jar with the rest of the movie, which is fairly light overall, and does it give the audience the right clues about the tone of the scene which will unfold? We may not know the answers until we watch the whole film through.
Duncan has plenty more work to do on Above the Clouds, but I’m confident it’s in very good hands. I will probably attend another session when it’s close to completion, so watch this space for that.