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Creating the color of Hacksaw Ridge

Australian colorist Trish Cahill first got involved in the DI on Mel Gibson’s Hacksaw Ridge when cinematographer Simon Duggan enquired about her interest and availability for the film. She didn’t have to consider the idea long before saying yes.

Hacksaw Ridge, which earned Oscar nominations for Best Picture, Director, Lead Actor, Film Editing (won), Sound Editing and Sound Mixing (won), is about a real-life World War II conscientious observer, Desmond Doss, who refused to pick up a gun but instead used his bravery to save lives on the battlefield.

Trish Cahill

Let’s find out more about Cahill’s work and workflow on Hacksaw Ridge

What was the collaboration like between you and director Mel Gibson and cinematographer Simon Duggan?
I first met Mel and the editor John Gilbert when I visited them in the cutting room halfway through the edit. We looked through the various scenes and — in particular, the different battle sequences — and discussed the different tone that was needed for each.

Simon had already talked through the Kodachrome idea with a gradual and subtle desaturation as the film progressed and it was very helpful to be spinning through the actual images and listening to Mel and John talk through their thoughts. We then chose a collection of shots that were representative of the different looks and turning points in the film to use in a look development session.

Simon was overseas at the time, but we had a few phone conversations and he sent though some reference stills prior to the session. The look development session not only gave us our look template for the film but it also gave us a better idea of how smoke continuity was shaping up and what could be done in the grade to help.

During the DI, Mel, John and producer Bill Mechanic came in see my work every couple of days for a few hours to review spools down. Once the film was in good shape, Simon flew in with a nice fresh eye to help tighten it further.

What was the workflow for this project?
Being a war film, there are quite a few bullet hits, blood splatter, smoke elements and various other VFX to be completed across a large number of shots. One of the main concerns was the consistency of smoke levels, so it was important that the VFX team had a balanced set of shots put into sequence reflecting how they would appear in the film.

While the edit was still evolving, the film was conformed and assistant colorist Justin Tran started a balance grade of the war sequences on FilmLight Baselight at Definition Films. This provided VFX supervisor Chris Godfrey and the rest of the team with a better idea of how each shot should be treated in relation to the shots around them and if additional treatment was required for shots not ear-marked for VFX. The balance grading work was carried across to the DI grade in the form of BLGs and were applied to the final edit with the use of Baselight’s multi-paste, so I had full control and nothing was baked in.

Was there a particular inspiration or reference that you used for the look of this film?
Simon sent through a collection of vintage photograph references from the era to get me started. There were shots of old ox blood red barns, mechanics and machinery, train yards and soldiers in uniform — a visual board of everyday pictures of real scenes from the 1930s and 1940s, which was an excellent starting point to spring from. Key words were desaturated, Kodachrome and, the phrase “twist the primaries a touch” was used a bit!

The film starts when our hero, Desmond Doss, is a boy in the 1930s. These scenes have a slight chocolaty sepia tone, which lessens when Doss becomes a young man and enters the military training camp. Colors become more desaturated again when he arrives in Okinawa and then climbs the ridge. We wanted the ridge to be a world unto itself — the desolate battlefield. Each battle from there occurs at different times of day in different environmental conditions, so each has been given its own color variation.

What were the main challenges in grading such a film?
Hacksaw Ridge is a war film. A big percentage of screen time is action-packed and fast-paced with a high-cut ratio. So there are many more shots to grade, there are varied cameras to balance between and fluctuating smoke levels to figure out. It’s more challenging to keep consistency in this type of film than the average drama.

The initial attack on top of the ridge happens just after an aerial bombing raid, and it was important to the story for the grade to help the smoke enhance a sense of vulnerability and danger. We needed to keep visibility as low as possible, but at the same time we wanted it still to be interesting and foreboding. It needed analysis at an individual shot level: what can be done on this particular image to keep it interesting and tonal but still have the audience feel a sense of “I can’t see anything.”

Then on a global level — after making each shot as tonal and interesting as possible — do we still have the murkiness we need to sell the vulnerability and danger? If not, where is the balance to still provide enough visual interest and definition to keep the audience in the moment?

What part of the grading process do you spend most of your time on?
I would say I spend more time on the balancing and initial grade. I like to keep my look in a layer at the end of the stack that stays constant for every shot in the scene. If you have done a good job matching up, you have the opportunity of being able to continue to craft the look as well as add secondaries and global improvements with confidence that you’re not upsetting the apple cart. It gives you better flexibility to change your mind or keep improving as the film evolves and as your instincts sharpen on where the color mood needs to sit. I believe tightening the match and improving each shot on the primary level is time very well spent.

What was the film shot on, and did this bring any challenges or opportunities to you during the grade?
The majority of Hacksaw Ridge was shot with an Arri Alexa. Red Dragon and Blackmagic pocket cameras were also used in the battle sequences. Whenever possible I worked with the original camera raw. I worked in LogC and used Baselight’s generalized color space to normalize the Red and Blackmagic cameras to match this.

Matching the flames between Blackmagic and Alexa footage was a little tricky. The color hues and dynamic range captured by each camera are quite different, so I used the hue shift controls often to twist the reds and yellows of each closer together. Also, on some shots I had several highlight keys in place to create as much dynamic range as possible.

Could you say more about how you dealt with delivering for multiple formats?
The main deliverables required for Hacksaw Ridge were an XYZ and a Rec709 version. Baselight’s generalized color space was used to do the conversions from P3 to XYZ and Rec709. I then made minimal tweaks for the Rec709 version.

Was there a specific scene or sequence you found particularly enjoyable or challenging?
I enjoyed working with the opening scene of the film, enhancing the golden warmth as the boys are walking through the forest in Virginia. The scenes within the Doss house were also a favorite. The art direction and lighting had a beautiful warmth to it and I really enjoyed bringing out the chocolaty, 1930’s and 1940’s tones.

On the flip side of that I also loved working with the cooler crisper dawn tones that we achieved in the second battle sequence. I find when you minimize the color palette and let the contrast and light do the tonal work it can take you to a unique and emotionally amplified place.

One of the greater challenges of grading the film was eliminating any hint of green plant life throughout the Okinawa scenes. With lush, green plants happily existing in the background, we were in danger of losing the audience’s belief that this was a bleak place. Unfortunately, the WW II US military uniforms were the same shade of green found in many parts of the surrounding landscape of the location, making it impossible to get a clean key. There is one scene in particular where a convoy of military trucks rolls through a column of soldiers adding clouds of dust to an already challenging situation.

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