Negative Lighting

There were no practicals in this corner of the pub, so we placed an 800 open-face outside the window, gelled with Midnight Blue, and a 1×1′ LED panel in the wood-burner, gelled with CTO.

This year I’ve shot a couple of productions on the Sony FS7, a camera I’ve been very impressed by. Its most interesting feature is its high native ISO of 2000, which makes quite an impact on how you go about lighting. The light shed by practicals is often enough to illuminate a scene, or a large part of it, and sometimes you need to take existing practicals away in order to maintain contrast and shape, similar to how you take ambient light away (negative fill) when shooting exteriors.

It’s a strange thing about being a DP that, yes, sometimes you’re required to plan a mammoth lighting set-up using tens of kilowatts of power, but other times it’s just a case of saying, “Take the bulb out of that sconce.” You’re working to exactly the same principles, using your creative eye just as much in both scenarios.

Let’s look at some examples from a promotional film I shot with director Oliver Park for Closer Each Day, an improvised stage soap.

Our location was a pub, which had a large number of existing practicals: mainly wall sconces, but some overheads above the bar and in the corridors too. The film had to be shot in a single night, entirely on Steadicam, with some shots revealing almost the whole room, and to further complicate matters I was a last-minute hire due to another DP having to step down. Keeping the lighting simple, and avoiding putting any “film lights” on the floor where the roving camera might see them, was clearly the way to go.

I identified the darker areas of the room and added a few extra sources: two blue-gelled 800s outside the windows, an orange-gelled 1×1′ LED panel in the wood-burner, an LED reporter light in one key corner, and a small tungsten fresnel toplight onto a key table, firing down from the mezzanine so it would never be in shot. Other than those, and a low level of fill bounced off the ceiling, we relied exclusively on the existing practicals. (They were mainly fluorescent, and ideally we would have reglobed these all with tungsten, but it wasn’t possible.)

This view from the mezzanine shows the diffused 300W fresnel top-lighting the drinking contest table, and the black-wrapped 650 firing into the ceiling for fill.

 

So, that’s the “positive” lighting. Here are three examples of “negative” lighting in the film…

When Big Dick Johnson (yep, that’s the character’s name) first enters the pub, I put a piece of tape over a little halogen spotlight just above his point of entry. This was partly because it was very bright and I didn’t want him to blow out as he walked under it, but it also made for a much better sense of depth in the overall shot. As I’ve often mentioned on this blog, the best depth in an image is usually achieved by having the foreground dark, the mid-ground at key and the background bright. Killing the halogen spotlight helped create this progression of brightness and therefore depth. It’s also just nice in a shot like this to come out of darkness into the light, enhancing the reveal of the new space to the viewers.

When Billy De Burgh scrambles to buy a ticket at the box office, there are two practicals just above his head. Depending on which way we were shooting, I de-globed one of the fixtures – always the one closest to camera. This ensured that Billy always had backlight, and never had a really hot, toppy front-light shining harshly down on him.

On a side note, the blue light inside the box office was existing – I guess they were using cool white LED bulbs in there – and I really like the way it differentiates the spaces on camera. It puts the bored ticket-seller in a cold, detached world very separate to Billy’s warmer, more urgent world.

This doorway where Big Dick ends the film had sconces on both sides. It’s never very interesting to have an actor evenly lit on both sides of their face, and especially as Dick is such a tough, unpleasant character, I felt that more contrast was required. I chose to remove the globe from the righthand sconce, so that when he turns camera left to look at the sign he turns into the remaining sconce, his key-light. We filled in the other side of his face a tiny touch with a reflector.

I would love to have been able to exercise the same control over the street-lamps in the opening scene of the film – some of them are quite flat and frontal – but unfortunately time, budget and permissions made that impossible. We would have needed huge flags, or a council-approved electrician to switch the lamps off.

That’s all for today. Next time you’re in Bristol, check out Closer Each Day. I didn’t get chance to see it, but I hear it’s brilliant.

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Negative Lighting

The Cinematography of “Perplexed Music”

In June I was recommended by a mutual friend to shoot a short drama called Perplexed Music, inspired by the Elizabeth Barrett Browning sonnet of the same name. It’s a passion project from writer-director Mark McGann, with his brother Paul McGann (Doctor Who, Alien 3, Withnail & I) in the lead role of a man grieving for his deceased partner.

Paul and Mark pose with one of the supporting artists between takes.

Mark was keen from the outset to shoot on an Alexa, and I was quick to agree. Arri Rental very kindly gave us an amazing deal on an Alexa Classic and a set of Ultra Primes. As on Above the Clouds, we used a Blackmagic Micro Cinema Camera as a B-cam, capturing two specific angles that were impossible on the Alexa with our limited grip budget.

Throughout July, Mark and I had a very satisfying creative dialogue about the cinematic techniques we would use to tell the story of Paul’s character, The Man, who never speaks. I had been watching a lot of Mr. Robot, and was keen to use unusual compositions as that show does. The visual grammar that we ultimately developed eschewed The Rule of Thirds, either squeezing The Man right into the side of frame – at times when things are too much for him – or placing him dead centre for moments of clarity and acceptance, and for flashbacks to when his partner was alive.

The Blackmagic Micro Cinema Camera is mounted on a combo lighting stand to capture a high angle through a streetlamp.

While testing lenses at Arri Rental a few weeks prior to the shoot, I took the opportunity to shoot some frame-rate tests between 24 and 48fps. Since the film has so little dialogue, I figured there was nothing to stop us using a lot of slow motion if we wanted to. I didn’t want it to look like a music video though. I thought perhaps a very subtle over-cranking, creating languid blinks and slightly heavier movement, would add to the burden of The Man’s grief. Mark agreed as soon as he saw the tests, and we ended up shooting a number of set-ups at 28 and 30fps, plus 40fps for a pivotal sequence.

I also tested various ISO settings on the Alexa (click here for full details, stills and video from this test). Based on these, I decided to use ISO 1600 for the majority of the film, partly for the extra latitude in the highlights, and partly to add grittiness to The Man’s grief-stricken world, in the form of a little picture noise. When we started shooting the flashbacks, on the spur of the moment I decided to switch to ISO 400 for these. A few years back I shot the music video below on a Red Epic and, for reasons I forget, one set-up was done at a lower ISO than the rest. I remember the feeling this gave, when I saw the final edit, of everything suddenly being smooth and hyper-real. (You can just about it discern it through the Vimeo compression at 1:48.) I thought that would be a great feeling to give to the flashbacks.

1st AC Rupert Peddle and 2nd AC Ben Davies set up a lakeside close-up under a diffusion frame which will soften the light on Paul.

Much of Perplexed Music was day exterior, but a couple of sequences required lighting. In the opening café scene, I fired HMIs through two windows, but kept their light away from The Man, keying him with a practical to put him in his own little world. Meanwhile, a happy couple he’s watching are bathed in sunlight (sometimes real, sometimes not) warmed up with a quarter CTO, and bouncing beautifully off their table to give them a healthy glow.

For night interiors at The Man’s home, I was keen to rely on practicals as much as possible. Firstly there wasn’t much space in the little cottage, secondly I didn’t want the hassle of having to shift them around to keep them out of frame when we changed angle, and thirdly it just looks more natural. So aside from a tungsten bounce in a corner of the living room we knew would never be seen, I stuck to practical table lamps and exterior lighting.

Setting up for a night exterior shot. Photo: Gary Horton

I had planned to use direct HMI sources for moonlight through the windows, but my gaffer Sam suggested going softer so that we wouldn’t have hard shadows inside which would need filling. I saw that he was right, so we used a kino through one window and a 2.5K HMI bounced into poly through another (pictured at left).

Perplexed Music was shot over five days in Frome in Somerset and Rame in Cornwall. The latter provided us with a spectacular cliff-top and the isolated St. Michael’s Chapel on the peak of the headland. Here we employed the services of The Fly Company, who captured two dramatic, sweeping shots on their DJI Inspire 2 drone. We were all extremely impressed by what they were able to achieve, especially as it was done in very windy conditions, in between rain showers.

We completed the final set-ups of the schedule as the winds began gusting up to 60mph, and poor Paul could barely stand upright! I was certainly glad we picked the Alexa to shoot on, because anything lighter would probably have shaken during takes, if not blown over!

Lining up a shot with director Mark McGann. Photo: Gary Horton

I had a fantastic time working with Mark and Paul, and the whole cast and crew. We were sad to part ways at the end of the week, and we all look forward to seeing the finished film soon. And at this point, dear reader, I ask for your help. Currently a Kickstarter campaign is underway for postproduction. It’s well over 50% funded at the time of writing, but every little helps in our quest to reach the finishing line. Rewards for backers include thank you video messages from Paul and Mark, and tickets to a private screening in December. Even if you can’t contribute, please consider sharing the page on social media. Thanks!

https://www.kickstarter.com/projects/perplexedmusic/perplexed-music-post-production

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The Cinematography of “Perplexed Music”

Alexa ProRes ISO Tests

My Cousin Rachel

I’ve shot three features on Arri Alexas, but I’ve never moved the ISO away from its native setting of 800 for fear of noise and general image degradation. Recently I read an article about the cinematography of My Cousin Rachel, in which DP Mike Eley mentioned shooting the night scenes at ISO 1600. I deliberately set off for the cinema in order to analyse the image quality of this ISO on the big screen. Undoubtedly I’ve unwittingly seen many things that were shot on an Alexa at ISO 1600 over the past few years, but this was the first time I’d given it any real thought.

To my eye, My Cousin Rachel looked great. So when I was at Arri Rental the other week testing some lenses, I decided to shoot a quick ISO test to see exactly what would happen when I moved away from the native 800.

But before we get to the test footage, for those of you unsure exactly what ISO is, here’s an introduction. The more experienced amongst you may wish to skip down to the video and analysis.

 

What is ISO?

ISO is a measure of a camera’s light sensitivity; the higher the ISO, the less light it requires to expose an image.

The acronym actually stands for International Organization for Standardization [sic], the body which in 1974 combined the old ASA (American Standards Association) units of film speed with the German DIN standard. That’s why you’ll often hear the terms ISO and ASA used interchangeably. On some cameras, like the Alexa, you’ll see it called EI (Exposure Index) in the menus.

A common ISO to shoot at today is 800. One way of defining ISO 800 is that it’s the sensitivity required to correctly expose a key-light of 3 foot-candles with a lens of T-stop 1.4 and a 180° shutter at 24fps, as we saw in my Barry Lyndon blog.

If we double the ISO we double the effective sensitivity of the camera, or halve the amount of light it requires. So at ISO 1600 we would only need 1.5 foot-candles of light (all the other settings being the same), and at ISO 3200 we would need just 0.75 foot-candles. Conversely, at ISO 400 we would need 6 foot-candles, or 12 at ISO 200. Check out this exposure chart if it’s still unclear.

ISO is one of the three corners of the Exposure Triangle, well-known to stills photographers the world over. You can read my posts on the other two corners: Understanding Shutter Angles and F-stops, T-stops and Optical Density.

Just as altering the shutter angle (exposure time) has the side effect of changing the amount of motion blur, and altering the aperture affects the depth of field, so ISO has its own side effect: noise. Increase the ISO and you increase the electronic noise in the picture.

This is because turning the ISO up causes the camera to electronically boost the signals it’s receiving from the sensor. It’s exactly the same as turning up the volume on an amplifier; you hear more hiss because the noise floor is being boosted along with the signal itself.

I remember the days of Mini-DV cameras, which instead of ISO had gain; my Canon XL1 had gain settings of -3dB, +6dB and +12dB. It was the exact same thing, just with a different name. What the XL1 called 0dB of gain was what today we call the native ISO. It’s the ISO at which the camera is designed to give the best images.

 

ISO and Dynamic Range

The Alexa has a dynamic range of 14 stops. That means it can simultaneously record detail in an area of brightness x and an area of brightness times 2 to the power 14. At its native ISO of 800, those 14 stops of dynamic range are equally distributed above and below “correct” exposure (known as middle grey), so you can overexpose by up to 7 stops, and underexpose by up to 7 stops, without losing detail.

If you increase the ISO, those limits of under- and overexposure still apply, but they’re effectively shifted around middle grey, as the graphic to the left illustrates. (The Pro Video Coalition post this graphic comes from is a great read if you want more detail.) You will see the effects of this shifting of dynamic range very clearly in the test video and images below.

In principle, shooting at ISO 1600 is the same as shooting at ISO 800, underexposing by a stop (giving you more highlight detail) and then bringing it back up a stop in post. The boosting of the signal in that case would come right at the end of the image path instead of near the beginning, so the results would never be identical, but they’d be close. If you were on a bigger project with a DIT, you could create a LUT to bring the exposure up a stop which again would achieve much the same thing.

All of the above assumes you’re shooting log ProRes. If you’re shooting Raw then everything is simply recorded at the native ISO and any other ISO you select is merely metadata. But again, assuming you exposed for that other ISO (in terms of iris, shutter and ND filters), you will effectively get that same dynamic range shift, just further along the pipeline.

If this all got a bit too technical for you, don’t worry. Just remember:

Doubling the ISO

  • increases overall exposure by one stop,
  • gives you one more stop of detail in the highlights,
  • gives you one less stop of detail in the shadows, and
  • increases picture noise.

Halving the ISO

  • decreases overall exposure by one stop,
  • gives you one less stop of detail in the highlights,
  • gives you one more stop of detail in the shadows, and
  • decreases picture noise.

 

The Test

I lit the subject, Rupert “Are You Ready?” Peddle, with a 650W tungsten fresnel bounced off poly, and placed a 40W candle globe and some LED fairy lights in the background to show highlight clipping. We shot the tests in ProRes 4444 XQ on an Alexa XT Plus with a 32mm Cooke S4, altering the shutter angle to compensate for the changing ISOs. At ISO 400 the shutter angle was maxed out, so we opened the lens a stop for ISO 200.

We tested five settings, the ones corresponding to a series of stops (i.e. doublings or halvings of sensitivity): 200, 400, 800, 1600 and 3200. I have presented the tests in the video both as recorded in the original log C (mislabelled as S-log, sorry!), and with a standard Rec.709 LUT.

You’ll need to watch the video at full-screen at 1080P to have any chance of seeing the differences, and even then you might see the compression artefacts caused by the noise more than the noise itself. Check out the stills below for a clearer picture of what’s going on. (Click on them for full resolution.)

 

Analysis

To me, the most important thing with every test is how skin tones are rendered. Looking at the original ProRes of these comparisons I think I see a little more life and vibrance in the skin tones at lower ISOs, but it’s extremely subtle. More noticeable is a magenta shift at the lower ISOs versus a green shift at higher ones. The contrast also increases with the ISO, as you can see most clearly in the log images.

At the lower ISOs you are not really aware of any noise in the picture. It’s only at ISO 1600 that it becomes noticeable, but I have to say that I really liked this level of noise; it gives the image a texture reminiscent of film grain. At ISO 3200 the noise is quite significant, and would probably be unacceptable to many people.

The really interesting thing for me was the shifting of the dynamic range. In the above comparison image, look at the globe in log – see how it starts off as one big white blob at ISO 200 and becomes more detailed as the ISO rises? Now look at the dark wall around the globe, both here and in the previous image – see how it subtly and smoothly graduates into darkness at the lower ISOs, but becomes a grainy mess at the higher ones?

I can see an immediate benefit to shooting at ISO 1600 in scenes lit predominantly with practicals. Such scenes tend to have a low overall level of illumination, while the practicals themselves often blow out on camera. Going to ISO 1600 would give me extra exposure and extra detail in the practicals. I would be sacrificing shadow detail, so I would have to be a little more careful not to underexpose any faces or other important elements of the frame, but I can deal with that. In fact, I often find myself determining my exposure in these types of scenes by how blown out the practicals are, wishing I could open up a little more to see the faces better but not wanting to turn the lamps into big white blobs. Increasing the ISO would be the perfect solution, so I’m very glad I did this test to alleviate my ungrounded fears.

What about scenarios in which a lower-than-native ISO would be useful? Perhaps a scene outside a building with an open door, where the dark interior is visible in the background and more detail is required in it. Or maybe one of those night scenes which in reality would be pitch black but for movie purposes have a low level of ambient light with no highlights.

I hope you’ve found this test as useful and interesting as I have. Watch this space or subscribe to my YouTube Channel for the lens test.

Thanks to Rupert Peddle, awesome steadicam op and focus puller – check out his site at pedhead.net – for appearing in front of the lens. Thanks also to Bex Clives, who was busy wrangling data from the lens tests while we were shooting these ISO tests, and of course Arri Rental UK.

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Alexa ProRes ISO Tests