A Study In Colour, Curves & Saturation Posted Sunday, September 16, 2012 By Nick Bedford
I’ve mentioned before that I’m working on a few music video projects behind the scenes and have been self-teaching myself cinematography to help with that. Photography seemed liked a natural step towards adding motion to the equation, and all that comes with it.
(warning: science to follow… I mean art)
As director and photographer on my own small projects, this involves taking on the aspects of lighting, filming, editing, and colour grading and over the course of the last six months or so of learning, I’ve become acutely aware of the difference between the look of many major motion pictures shot in film, and the look of most colour grades in digital photography. There’s some subtle things that are happening in the way film (different for every stock, of course) captures light and colour and how this information is developed in the lab.
Digital sensors on the other hand must be massaged in the colour grade to achieve a look that has the heart of what film gives cinematographers. Digital cinema cameras are phenomenal these days. The ARRI Alexa, for example, is one of the first cameras to truly make veteran film cinematographers rethink their choice of camera.
But one of the main reasons why this is happening is because the images, after careful colour grading, can rival the colour, contrast and saturation properties of the film stocks they’ve loved filming on. I’m fascinated with the way these film stocks reproduce the colours and contrast of the real scene, and I’ve also been trying to reproduce these properties to some extent in colour grading digital footage.
Contrast & Saturation
Digital cinematography often involves shooting to a very flat image profile that captures all the information the sensor has to offer. Whether capturing in a raw format or in a compressed format, storing the dynamic range of the sensor’s image to its full extent allows the colourist (whether that’s a separate person or not) to achieve any look they want to complement the intentions of the film.
Just take this example of how I colour graded a frame that John Brawley shot in ProRes on the new Blackmagic Cinema Camera. The top is the image that is presented after shooting the footage. It looks flat and desaturated, and it’s this way for a very good reason. The bottom image is the result of my own colour grading efforts in Final Cut Pro X with some considerations from my findings in the way film generally responds to aspects like saturation over luminance, colour and gamma.
You might think that this involves nothing more than an extreme contrast bump and a bump on the saturation, and you’re mostly right. But there’s more at work that just two sliders. I work in Final Cut Pro X for the most part and there’s a few things I did to arrive at this grade.
First, I inverted the logarithmic contrast by pushing the midtones right down, almost to 90% under, then I carefully tweaked the shadow and highlight sliders to retain the shadow detail and prevent highlights from blowing to white. In reality the highlights didn’t get close to 100% white.
But here comes the major change in the way I’ve been thinking about saturation. What I’ve noticed in many films (and online videos that have been shot on film), that the saturation actually increases on its way to black (shadows) and decreases on its way to white (highlights). The above s one example of this saturation curve and I wish that more colour tools (such as Lightroom for photography) had this setting. DaVinci Resolve has a Saturation vs Luminance curve which allows you set the saturation as a function of how bright the image pixel is.
I tend to increase the shadow saturation about 75% and have the ramp towards desaturation in the midtones and highlights a little more subtle, probably under 50% at the highlights.
There are other subtle aspects of the colour in films that I’ve noticed besides saturation and white balance (warm, cool or neutral colour). Whether you enjoyed the film or not, Snow White & The Huntsman had stunning cinematography, and I loved the colour in the film.
What I noticed in this particular film is that there was a very subtle yellow tint to the highlights, and on the opposite side, a very subtle blue tint in the shadows. On average only 2-4% of a colour tint in the shadows, midtones and highlights was enough to achieve similar colour properties to this. Different film stocks have different subtle colour properties and this is only one particular instance that I’ve noticed recently. Take a look at this frame from the movie.
You can see the subtle colour tint in the shadows and highlights, and I found this throughout the entire movie.
See my example of various colour grades on John Brawley’s “Afterglow” footage.
I’ve always been a fan of the way film responds in it’s colour, contrast and saturation. It’d be great to one day shoot something on film, but for now I’m going to settle for the Blackmagic Cinema Camera that I pre-ordered and using DSLRs. I hope you were able to follow what I was on about and perhaps learn something! I spend a lot of time making sure the colour of my photos and now videos are exactly what I want and here is what I’ve stumbled upon lately.
Make sure to comment with your thoughts too