How to Maximize Your Dynamic Range with the ARRI Alexa Mini
Digital cinema cameras have improved the way in which cinematographers properly light, construct and expose a scene. However, with all the "new" tools at every DP's fingertips, has it become easier or more complicated? ISOs, LUTs, waveforms, false-color and the list goes on. What do all of these mean? And how should a modern-day cinematographer, use these tools to maximize their dynamic range when on set.
In short, dynamic range refers to the range of which a camera can successfully capture the lightest and darkest areas of an image without losing detail (Source: Vimeo). It wasn't too long ago that this was the flagship argument for shooting on film. However, since the takeover of digital cinematography, dynamic range has become the go-to differentiating factor from brand to brand, camera to camera.
Insert Megan Stacey. Megan is an incredibly talented cinematographer out of Los Angeles who was kind enough to take us through her process of lighting a moody scene full of contrast. With the ARRI Alexa Mini, we were able to show how to take advantage of our dynamic range to set you up for success in post. Megan and I were lucky to have a number of talented ShareGrid members on hand to shoot in the beautiful facility of ShareGrid member, AJ Martinson of Martinsound Studios and film the talented pianist and actor, Sam Neagley.
Without further ado, here are 7 ways to maximize your dynamic range on the ARRI Alexa Mini.
1. Know Your LUT
LUTs or Look Up Tables, are a great way to not only give you and your creative team a "look" to references as you shoot, but its also a way to set boundaries for yourself. As Megan puts it, you can shoot with a LUT to protect highlights and shadows because you are then lighting and exposing your scene per that LUT. On our shoot, Megan used her own LUT that offered a more contrasty or "crunchy" look which mean the shadows and highlights were showing less fidelity than what you'd see in a Log C look. By doing so, you are affording a little more room in post for both your shadows and highlights if you light to that "contrasty" look.
2. Understand Your ISO
Just like a LUT, knowing how to use your ISO is paramount. The ARRI Alexa Mini's native ISO is 800. This means its most dynamic range exists at 800. The rule of thumb with ISO typically is, the lower the ISO, the more information is retained in shadows, yet less in the highlights. The same can be said for higher ISOs and highlight retention.
Typically, an Alexa Mini sensor is close to 7 over 7 under if you’re using ISO 800. For ISO 400 it is 6 over 8 under. So, your latitude range stays the same but the midpoint moves based on your ISO. In our case, we shot at an 800 ISO because we were confident in our shadows not being too dark that we couldn't capture any information out of them. Plus, this afforded us more fidelity in the highlights. However, some may argue that a dark scene like this, a 500 ISO would be ideal because you can now capture more information in the shadows at a lower ISO. The only drawback is of course, less room in the highlights.
There is no perfect answer for this one. It is purely personal preference, balanced with the scene you're shooting, resources on set and what your post-workflow may be like.
3. Use a Far-side Key
One of the most difficult and yet rewarding challenges of cinematography 101 is keeping the key light on the far-side of your subject. Yes, it is very challenging, especially in a multiple-camera setup, but it offers a much more cinematic look in a number of ways. This certainly isn't a must for all shooting situations, as front-lighting can often times be called for when organically, it makes sense. However, a far-side key is more often than not, the preferred method of lighting people for cinematographers.
In our shoot, we used a Source Four Leko light on a stand about 15 feet in the air. We were lucky to have flats and roll-away walls to place as needed. So we used a few of those to hide our light stand, yet our light was just above our frame in the wide shot.
4. Hot Spots = Richer Shadows
Often times, when you have a dark scene, the overall image can feel a little, well dark because so much of your frame is in shadow. However, for the human eye to feel as though we are watching a properly balanced and exposed scene, it can be helpful to add bright specular light sources to even out the overall contrast of the scene. In our scene, you can see a number of small, tungsten practicals in the background. We purposefully placed these there for a few reasons. One is for color contrast which is another tip worth noting. Our scene is predominantly cyan and blue so it's always good to exercise the ability to fill your frame with elements of the opposite color. In this case, we have warm tungsten, orange lights.
Secondly, we did this because it fills mostly dark areas of the frame with bright elements. This re-enforces the appearance of strong contrast and gives our blacks or shadows a richer look.
Last, it also offers depth to the scene, and gives each frame, more out of focus specular lights which can offer a simple scene more dimension and the appearance of a bigger world.
5. Use Haze
Haze or fog is used in more shoots than you'd think. One way to take the sharpness off of digital sensors is to add haze to your environment. We used haze not only to emphasize the source of our key light (which gives a dramatic effect to the scene) but it also lifts the blacks of our scene which gives us more room in post to manipulate. In short, it lowers the overall contrast of the image which is another way to increase one's dynamic range when it comes time to color-grade.
However, be careful. Haze can easily reveal where your lights are located. This is made abundantly clear in our video as you can see our key light is coming from the top right of the frame. That same logic can be made possible from fill lights and other sources you may not want the audience to "feel" in the frame.
In this shoot, we would run the haze machine for a 20-30 seconds and let the haze settle before we would roll. Practicing and understanding the thickness of haze is an underrated technique worth mastering on set.
6. Use Negative Fill
Too often, I see filmmakers adding light to scenes as a solution to a lighting problem. I've been guilty of that many times. However, by practicing and understanding the power of negative fill, you can quickly learn that taking away light can be just as effective if not more! In today's day and age of light sensitive cameras, you can rely on your sensor and its ability to capture enough information for your final image.
Negative fill is when you use dark non-reflective surfaces to absorb and prevent light from hitting or reaching your subject. To better explain what I mean, we used a 4x4 floppy solid flag just outside of the frame for our close ups of Sam, our pianist. Otherwise, the haze and other lighting elements would have created a flatter look on Sam's face...which is something we didn't want.
Though this actually increases the contrast on your subject's face, it is certainly one way to take advantage of the dynamic range your camera offers. The rookie mistake seems to resort to adding light to scenes when there's an issue. However, the best in the industry find ways to simplify their setup and take away light as a solution. Using negative fill is one of the cheapest, fastest and easiest way to increasing contrast and shape light on your subject.
7. Test Your Camera
I may start to sound like a broken record, but the most important thing you can do to determine dynamic range, and how to shoot for your project, is to test! Rent a camera or ask a rental house to run tests on some of their gear. Only you will know what kind of shooting environment you will be in, what kind of budget you're working with and what kind of post work-flow you'll have waiting for you on the other end. Take all of that into account and run your own tests. We hope this video has been helpful and inspiring to some. However, most importantly, we hope that it encourages all to conduct their own further tests before a shoot.
Yes, the Alexa Mini is an expensive camera and we are not trying to encourage those who can't afford such a camera to give up or not take these tips as inspiration. Every camera has its dynamic range, and therefore, its own limitations. From DSLRs, to mirrorless, to RED, Sony, Canon and Blackmagic. All brands, sizes, styles and models have their own unique characteristics. But its up to you to make it look awesome!