HDR, or High Dynamic Range, is a term we hear a lot in filmmaking these days. From TVs to external monitors, to camera specs and editing software, HDR is a growing area of interest. But if you haven’t had an opportunity to dive into HDR, how do you learn what it is and where to begin?
Luckily for you, we have a few different courses that touch on HDR within their lessons. If you want a well-rounded approach to understanding HDR, as well as a few varying opinions on how to maximize its potential, then take a look at a few of these modules. All of them are available to stream as part of an MZed Pro subscription.
Here are brief summaries of a few MZed courses and their discussion about HDR.
Cinematographer Karl Walter Lindenlaub is comfortable with jumping into new visual languages. He shot Independence Day and Stargate in such a way that the larger-than-life science fiction elements blend naturally with emotional, character-driven scenes.
In an in-person masterclass from ARRI Academy, Karl skipped the HDR technical discussion and went right into hands-on demonstrations of high contrast lighting and framing. HDR - or high dynamic range - is the ability to visualize a wider spectrum of light and dark in a single frame. In the past, a cinematographer might avoid shooting against a bright window for fear of blowing out the highlights or losing detail in the shadows. But in this course, Karl showed class participants how to embrace this new era by pushing the boundaries of dynamic range.
HDR development is led by content producers
At the beginning of this ARRI masterclass, class participants also got a short lesson in HDR and ARRI’s take on the subject. HDR first appeared at CES 2015 with monitors, followed by Dolby theaters, LG displays, and now on our smartphones. The first ARRI ALEXA in 2010 already had the ability to shoot HDR - in fact every ARRI digital camera ever made could shoot HDR - but there was no way to show it until the display technology caught up to the recording specs.
And along with the displays, we’ve also been fortunate to have content distribution channels that can output HDR, like Amazon Prime, Netflix, Apple TV, and Ultra HD Bluray. The timing of all the tech advancements and consumer demand for higher quality imagery has resulted in a perfect storm for HDR.
With HDR, we get darker blacks and brighter whites, more contrast, more depth, more vibrant colors, and sharper visuals with more details. It also means there are more stylistic looks possible than ever before.
But what about 4K and the race to high resolution imagery? Hasn’t that been the focus for cameras, TVs, screens, and filmmaking production standards?
The truth is that the big content buyers are leading the direction for content producers. So while Netflix has been pushing 4K acquisition for all of its original programming, Amazon has actually removed the 4K requirement and let producers decide what camera specs suit their needs best. As a result, many shows have switched to shooting with ARRI ALEXA, because ARRI has the highest dynamic range of any production camera, thanks (in part) to the large photosites on ARRI camera sensors.
But don’t worry, HDR content is increasingly combined with UHD 4K distribution, so most likely you won’t have to choose which direction will drive the future of your video and film production.
Even if you’re not in a place to be shooting HDR content right now, we’re undoubtedly moving towards greater dynamic range for both acquisition and viewing. It's important to learn from cinematographers who are pushing the boundaries in image acquisition.
Note: "High Dynamic Range with Karl Walter Lindenlaub ASC" was an ARRI master class taught at an in-person workshop. A web version was available for a limited time, but is no longer viewable.
ARRI Certified Training for Camera Systems
In the final lesson of ARRI Academy’s certified camera training course, instructor Florian Rettich discusses HDR in a way that is informative and helpful even if you’re not shooting on ARRI cameras.
To provide a little context, Florian describes HDR as images that have higher dynamic range than previously, similar to when we went from standard definition to high definition. So, there’s no actual number given - HDR doesn’t tell you how much more dynamic range you get. It’s just more than before.
But how much more than before? Well, SDR images in high definition means it uses the Rec.709 color space, which is designed for 5-8 stops, up to 10 in some rare scenarios. With HDR you’re seeing 14 or more stops of dynamic range. But it’s more than just a wider range of exposure. Way more.
What happens when you watch HDR-acquired content on an HDR screen is the image is much brighter, and therefore much more colorful, at least it looks more colorful to your eye. The image has the same hue and saturation as an SDR image, but the colors are displayed brighter, so your eyes perceive the image as more colorful.
And if you’re working with a brighter scene in general, your shot will look more natural, the way our eyes expect to see the image. If you’re shooting a dim scene with only four stops, HDR won’t provide much of a difference. But for daytime exteriors, HDR can make a scene come alive in ways we haven’t seen until now.
So in Florian’s opinion, HDR is not just another over-hyped feature contrived to sell more TV sets. You really can see the difference if you’re looking at two screens side by side. And as more consumers buy into the HDR difference, our industry needs to be able to standardize HDR content delivery, as well as iron out any lingering misunderstanding about High Dynamic Range.
HDR Standards Are Still Developing
As we get further into the nitty gritty about HDR in this lesson, we start to learn a little more about the gray areas. It’s still a developing technology and industry standards haven’t been widely agreed on...yet.
Before you can monitor HDR, you have to capture it, and ARRI has that down pat. There’s no specific “HDR Mode” in ARRI cameras - it records a wide color gamut with high dynamic range by default. You do need to record the feed into an intermediate state, such as RAW or Log-C, before converting into a deliverable using one of the several flavors of HDR. And finally, you need to prepare the content for monitoring.
The muddiness with standards is not just the flavors of HDR recording but also its monitoring. Currently we have two displays for monitoring HDR - LCD and OLED. LCD has a backlight and can appear super bright, with a peak luminance of up to 4000 nits. OLED, however, only goes up to 1000 nits at the moment, but it has much better definition with fine details and contrast. So the same HDR image can appear differently on the two types of monitors.
In the cinema world, there are two ways of projecting HDR in a theater. There’s Dolby Cinema, which uses two projectors with a wide color gamut, and your film’s DCP has to be specifically encoded for Dolby output. And then there’s Eclair Colour.
There is also a new color space - EOTF (Electro Optical Transfer Function), which matches the output display in both color space and gamma curve. And there’s even two flavors of HDR gamma curves.
So how do you make sense of all these developing HDR standards? As a filmmaker, practically speaking you only need to focus on capturing good quality LOG or RAW images, and with good exposure, and then convert from a wide color gamut to a lower dynamic range with P3 gamut. Then when it comes to monitoring your HDR film, you can get into the finer details of output or projection.
One thing to note as you’re shooting HDR footage: be very careful with accurate exposure, because what you see when you’re shooting may not be what others will see down the road. Essentially, if you’re using all 14 stops of your camera during a scene, you can expect that most displays are not going to show all those stops, even HDR displays. So if you don’t give yourself any head and foot room, your audience may see clipping. One way to combat this discrepancy is to use false color in your monitor and make sure it’s displaying what’s going to the card in LOG, and not just what the camera sees.
So with HDR technology, whereas it’s exciting to start shooting high dynamic range scenes and push the boundaries of where stylistic decisions can go, we also need to be aware that HDR monitoring and projection is still new and there are still some growing pains to come.
The ARRI Academy certified training for large-format cameras course has a lot in common with the regular camera systems course. So, much of what we discussed about HDR above is presented in this course too, but with slight differences. And it’s within the minor variations that we come away with a little more knowledge about HDR than we had before.
Instructor Florian Rettich begins the discussion by comparing high dynamic range in photography vs filmmaking. With still photography, you can bracket images to combine exposures, which allows you to capture a lot of information in both the shadows and highlights of a scene. But with motion picture cameras, there’s a time difference between two frames, and both the subject and the camera can be moving.
So to achieve an HDR image, ARRI cameras use dual gain architecture in the sensor to capture 14 or more stops of dynamic range, with any frame rate or panning speed. In essence, the camera is simultaneously capturing two read-outs from each pixel: one capturing the regular signal, and the other capturing lower-amplified information that is clipped in the first read-out.
The interesting part about this live HDR signal implementation is that ARRI has had it built into their digital cameras since 2010, and there’s no switch to turn it “on.” High Dynamic Range images are captured by default when recording RAW or Log-C. The main limitation, then, has been the ability to monitor HDR.
If you’re shooting HDR on set today, you’ll have to get past a few technical challenges because most likely you’ll have a few different monitors. So you might have an HDR look file inside the camera, which converts Log-C and Rec.2020 to one of the flavors of HDR EOTF, which then matches the color space of the output. But that might be your director’s monitor, while the operator is using an SDR Rec.709 eyepiece, so the camera has to have a secondary SDR look file to output correctly to the operator’s viewfinder as well.
It’s certainly a challenge to bounce between SDR and HDR monitoring on set, but one of the more common issues right now is the problem of presenting HDR content to viewers on SDR screens. Namely, how do you create online tutorials about HDR, or illustrate the differences of HDR, or simply showcase what you’ve created, when the viewer is on an SDR screen?
To demonstrate the HDR difference, the course invites you to watch the above Nike ad. In order to showcase the differences, the ad intentionally pushes the contrast a little to emphasize the shadows or brightness. So while you may not experience the images truly if you’re not on an HDR screen, you get a sense of how much brighter and colorful an HDR image looks like.
Initially, the differences between SDR and HDR can be striking to your eyes. But if you don’t compare them for a while, you eventually become acclimated to the HDR image and it appears simply normal. However, when you switch back to SDR, that’s when you notice the profound difference.
The bright parts in an HDR image are up to 10 times as bright as they used to be in SDR, while still maintaining more detailed information than SDR. That’s a phenomenal upgrade, and it’s exciting to be part of this major shift forward in filmmaking. But we’re also not looking forward to the day when we dust off the old SDR videos and exclaim, “What were we thinking?”.
After a technical dive into HDR with the two ARRI Academy courses, it’s good to step back and get a more visionary perspective on High Dynamic Range. In the last lesson of Mastering Color, we see instructor Ollie Kenchington meet up with another MZed educator, Philip Bloom, as they wander with their cinema cameras in search of HDR-worthy shots.
Both Ollie and Philip agree: HDR is the future of all delivery and coloring and shooting for film, video, and TV content. We’re still a little early but we might as well get a head start by figuring out everything we need to know now.
HDR is not just a gimmick, it’s truly a more realistic representation of the world. Until now, we’ve only been able to see a tiny amount of brightness around us. Cameras have been able to record with a Log curve for a while, which is a means of compressing dynamic range and fitting it within a smaller container. But now we are getting screens and delivery that allows us to see that additional brightness.
If you’re looking at a TV that has 4K and HDR, it’s the HDR that you’re going to notice that really makes the big difference.
One thing to remember with HDR is that you can still have clipped highlights. In fact, you don’t want things to look over processed. You want images to appear natural. The way our eyes work, you can’t look at the sun and also into a pool of dark shadows at the same time without our eyes adjusting for one or the other.
In the end, even if you don’t think you’ll shoot 10bit or RAW or HDR right now, you probably will before you know it, because the technology is moving so fast. Even some phones can shoot 10-bit HDR. There’s still work to do in terms of figuring out industry standards, and HDR monitors are still too expensive for most filmmakers, but we’re getting there.
Our cameras can now record more colors than our eyes can see. But until now, we’ve been unable to see the high quality, high dynamic range images that our cameras have been recording. With HDR capture and display, we can finally start moving towards an era in filmmaking that prioritizes light and vibrancy of images rather than resolution alone.
We hope you can learn a little about HDR with these courses that are part of MZed Pro - and if there’s anything you want to see with upcoming courses, let us know! Thanks!