Remember 2010, when we were all very excited about shooting in native 3D? Well, I think we can all agree that that trend is now dying a death, and ceding its Cool Trend crown to High Dynamic Range (HDR) imagery. However, HDR is different. Rather than a hyped up flash in the pan, it’s actually offering something that filmmakers have been clamouring for – a return to filmic production values, without losing the agility of digital shooting.
So what exactly do you need to know before you wade into the world of HDR content production? Can you shoot it with your current kit? And what does it really mean for your images? We asked our production team to give us the lay of the land.
First, for the newcomers: what is HDR?
So, the human eye has a functional range of roughly 100,000 nit from the darkest to brightest light it can perceive detail in, and the lens of a camera has a similar range. Until now, however, image processing, transmission and display technologies have reduced this range, meaning bright and dark objects that were perfectly visible to the naked eye appeared clipped or burned in a captured image. You could expose for the highlights and lose detail in the shadows, or expose for shadow but lose detail in the highlights, but there was no way to capture detail in both.
An HDR workflow preserves this full range from capture through transmission, all the way to final display, so your final image has the full dynamic range of the human eye, and therefore appears much more realistic and immersive, as shown in our illustration (alas, this will only work if you’re viewing this on an HDR-ready display). You’ll see more vivid colours, and more detail in shadows.
But to give some sense of the scale of this change, the brightest possible pixel on an HDR display is about 40 times what it used to be on an SD display, and when you’re working with an HDR image in post, you can tweak brightness levels pixel by pixel.
However, to get the full effect of HDR, you need more than a camera with a lot of latitude. For example, without support for a wide colour gamut, you won’t see as much colour variation in the newly visible section of your image. Support for high frame rates is also recommended, and you’ll need support for 10- or 12-bit capture too, depending on which version of HDR you’re working with.
There are competing versions of HDR?
Yep. The current frontrunner is HDR10, as it’s been picked up by various gaming platforms. Also popular is the more detailed Dolby Vision. The image displayed by Dolby Vision is ‘scene referred’, which means it varies from scene to scene, working with your display to adjust each image. By contrast, HDR10 is static.
Most consumer displays rely on Hybrid Log Gamma, an electronic-optical transfer function protocol that combines standard gamma with log to create (wait for it) a hybrid that extends traditional gamma beyond the standard curve. Any TV can display HLG, as it displays the standard gamma. TVs brighter than 100 nits (i.e. most LCDs) will then display more highlight information until it reaches its point of maximum brightness, when it’ll clip.
Which of these is the one my smartphone camera can do?
Neither. The ‘HDR’ advertised on smartphones is actually HDR-I, which uses tone mapping to give the impression that you’re seeing images with a higher dynamic range than you are. This is not the same as the true HDR you’ll be capturing on a pro camera for a production workflow.
So what qualifies a camera as being capable of shooting real HDR?
There are several features that your camera needs to qualify as HDR-capable, but the main ones are:
– 10-bit capture to Log or RAW. As a minimum, your camera needs to support ProRes or DNX 10-bit 4.2.2., but don’t feel like you have to stop there. The more bits the better, really.
– Plenty of latitude. Canon’s C300 MkII is being touted as having 15 stops, which is ideal, but the Sony FS7 and FS5 both have 14, and if you have a C500 in your arsenal, that still has a perfectly respectable 12 stops of dynamic range.
– S-Log3/C-LOG 3 capture capability; if you are shooting RAW and recording to Log over SDI, this needs to be 10-bit. 12-bit CinemaDNG capture is also good.
– Rec2020 gamut support.
Your existing camera may already be able to record S-Log3 with the help of an external recorder. (The Atomos Flame and Inferno series are a good bet for this, as they incorporate high quality HDR-ready monitors so you can see your footage accurately on set.)
Which cameras are HDR-ready?
Several such cameras are on, or at least making their way to, the market, but as we mentioned earlier, our favourites among the current crop are Canon’s C500 and C300 MK II, Sony’s FS7 and FS5, and the Panasonic GH4 and GH5. All of these cameras output a RAW signal that can be recorded as ProRes or DNX with the help of external recorder, and all have LOG gamma encoding.
Apart from a camera and maybe an external recorder, what else will I need?
In order to see what you’re doing with your HDR images in post, you will need a monitor that can support HDR. Currently, the simplest and most affordable are the Atomos Flame and Inferno ranges, which offer on-camera HDR monitoring combined with the ability to play back and edit your footage at full res, making a collaborative HDR workflow possible for everyone on set. If you’ve already invested in a Atomos Ninja Assassin, Blade HD, Flame, Shogun or Shogun Inferno, HDR support is available as a free upgrade, but as their screens only hit 500 nit, you won’t be able to see more than seven or eight stops of dynamic range; the newer monitors are 1500 nit and showcase 10 stops.
When it comes to post-production, we can’t in good conscience recommend grading on anything less than DaVinci Resolve. Its ability to power through high resolution and frame rate files without slowing down or falling over is going to be extremely necessary if you’re going to be tackling HDR, and it features the industry’s most advanced and sensitive HDR toolkit. The ability to grade a project for multiple colourspaces at the same time is going to come in handy until you’re delivering HDR 4K all the time, too.
Will my current infrastructure be OK?
To be honest, that depends how much 4K work you’ve done so far, and how many changes you’ve made to accommodate it. That 10-bit workflow with its attendant file sizes and frame rates means you’re going to want to be working on a 10Gb Ethernet network, rather than the standard 1GbE.
You’ll also want to make sure you have plenty of high capacity storage both at your facility and on set. One of the reasons we’re so keen on Atomos devices is that they’ve teamed up with G-Technology to develop the Master Caddy range. These high capacity SSDs can slot into any compatible Atomos recorder to capture your footage, then be removed and inserted in to an adaptor that makes them compatible with G-DOCK and ev series storage from G-Technology, so there’s no need for you to invest in proprietary recording media that’ll only work with one of your cameras (you’ll get better speeds and capacities this way, too).