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What 4K means for post production

Richard Wilding, general manager – Technology at Molinare looks at the issues surrounding the growth of 4K in post production

The 4K story actually began several years ago, and for facilities like Molinare who have been working in digital intermediate for feature films, resolution independent grading systems have been adopted over the past ten years or more, initially with scanned film supplying high resolution images.

But truth be told, 4K resolution productions were scarce in those early years and 2K was very much the mainstay for full-length features.

A decade on, 4K or even higher resolutions are seemingly commonplace – modern digital cameras are constantly developing and increasing pixel count is being touted as a major factor for improved imagery.

But improved definition needs more than pixels and that begins with the lens – high quality modern lenses may be deemed good enough to resolve 4K but the artistic use of older lenses or diffusion filters can reduce the captured resolution.

Then there is the camera sensor itself – is it really 4K? Bayer pattern sensors are widely used but they make a compromise in not having a red, green and blue value for every pixel site – instead they capture only one colour for each pixel and interpolate the other colours from those around it.

So a 4K Bayer sensor captures less than 4K resolution images and, while a 6K or higher Bayer sensor certainly does better, it is not the same as a sensor that captures RGB values for every pixel.

Impact on post

That said, what is the impact of 4K on post production? The media files are bigger simply because the pixel count is around four times greater than 2K or HD. The general impact of that is more storage is needed and transfer times are slower for the equivalent duration of media.

The ability of systems to playback and process the files is similarly affected, and technically assessing the images at full resolution requires high quality 4K displays or projectors that are currently rare.

In practice, this doesn’t mean that 4K is unworkable. Carefully planned storage management can help cope with the increased volume of media, and modern grading and editing systems perform much more smoothly with 4K images.

The increased demands of 4K for playback and storage do ‘rob’ us of some of the gains made by the natural progression of computing power and increasing affordability of data storage but, in time, we will make up that ground again.

The recent feature post production on Belle was an ideal opportunity for Molinare to trial an end-to-end longform 4K workflow. Ben Smithard, the DoP, choose to shoot on the Sony F65, which has a high resolution Bayer pattern sensor and, although the final delivery was 2K, we opted to undertake the whole post production in 4K to see what the benefits or pitfalls might be.

The outcome was that we found that the creative grade was not significantly hampered by the demands of the extra resolution and in some cases the finer detail made it easier to finesse complex grading of scenes.

Rendering took longer compared to 2K of course, and the resultant 4K files needed more storage, but the creative process was still fluid.

But 4K isn’t just about the cinema experience – it’s coming to our homes too. With TV set manufacturers pushing the sale of domestic 4K displays, and early-adopters, such as Netflix, providing 4K content, the rise of 4K UHD seems inevitable.

This may happen regardless of the consumer desire for the higher resolution but it’s not all just about pixel count – higher frame rates, typically 60 fps, are proposed and better image depth too. For many viewers, particularly those without massive screens, those other benefits may be the most appreciable – sport coverage, in particular, may highlight the benefit of improved motion delivered by higher frame rates.

So while 2K and HD production remains the mainstream, the use of 4K is certainly growing.

Post production facilities will need to continue adapting to meet the demands of higher resolution post and develop their systems and creative tools to meet the rising tide of 4K production for both feature film and broadcast television.


Posted 12 August 2014 by Richard Wilding
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  • General Manager - Technology, Molinare

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