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22/04/2013

Arguments For And Against 4K - Part One

The next generation of HD – 4K resolution – has been dividing those within the industry since its release, with many arguments for and against its use. Below, Barry Bassett, Managing Director at VMI.TV Ltd explains his thoughts on 4K.
The argument against 4K
Firstly, let me state that I am not against 4K. I agree that 4K images are stunning, only we need to be clear about what the reasons are, what the practicalities are, what the cost is and whether all of the hassle is actually worth the trouble right now in order to produce 4K images. That is the crux of my argument.
4K is not new – RED have been trailblazing 4K acquisition ever since the introduction of the RED One some years ago and this has been bolstered recently with the range of new cameras from Sony: the F-65 and the recent introduction of the PMW-F55, PMW-F5; RED: Epic, Scarlet and RED M-X and now the Black Magic Cinema Camera and even the Go Pro Hero 3. All of which claim to offer unrivaled image clarity and detail.
Firstly do we actually need 4K or UltraHD (UHD) as the consumer electronics industry is calling it?
Retiring HBO pioneer Bob Zitter doubts that consumers "barely notice the difference between 4K and existing HD on sets around 60in-70in in size", which Zitter reckoned would be the maximum size widely deployed. On this basis, the industry certainly need look no further than 1080p HD, which is double the resolution of 1080i or 720p, and is itself not widely deployed for linear TV delivery.
Again, the conventional wisdom within the industry is that 1080p HD does not deliver a substantial enough increase in quality over 1080i or 720p HD to be worth the effort of deploying across the content ecosystem, and that the logical next step forward would be to 4K.
John Galt, SVP Panavision claimed recently at a 2012 Creative Cow seminar that viewing 4K at normal theatre distances will result in you not being able to see sharpness at the pixel level as the pixels are too small. He concluded that, "…in order to see the detail provided by the pixels in a 4K image, you would need to sit in the first six rows of a theatre, otherwise you won’t see the extra image detail."
This is without acknowledging that many digital cinemas are only presently capable of displaying only 2K images right now.
His argument followed that, "We perceive edge sharpness as contrast between the edge and what’s behind it", so do we, the audience, really want a 4K image when HD does the job perfectly well. In many types of image – fast moving drama for instance, you can’t see the detail that 4K enables because the pictures are moving too fast. John Galt recommends, "If you want greater resolution, shoot at higher frame rates, not more pixels. We can achieve this now with existing HD technology and shoot at 48P instead of 24P, otherwise you simply create very high resolution images with a lot of image motion blur."
Whilst I am on the subject of high-resolution blurry images, it is virtually unheard of for top DoPs to shoot with very expensive lenses at extremely high resolution without inserting a softening piece of glass in order to reduce the sharpness of the images – how can 4K benefit the viewer under these conditions?
This is part of the 4K is not always 4K argument, where the devil of the detail is in the pattern… Debayering is the process of extrapolating colour information using a single sensor and has the result of reducing the colour detail, so that the actual resolution is less than the sensor promises.
This actually means that 4K images from a RED EPIC, whilst better than 4:4:4 HD, are not as ‘better’ as the numbers suggest. This is a very important point, as whilst the ARRI Alexa is not a 4K camera, it does use a 3.5K sensor.
As well as recording on-board to SxS cards in 1080, its de-bayered RAW output can be recorded on external devices at 2800 x 2160 - almost 3K. These RAW files offer improved dynamic latitude for excellent highlight control, as well as greatly increased resolution.
Skyfall was shot by Roger Deakins using the Arri RAW 2K+ workflow, with the output recorded by a Codex device. Versions were prepared for 4K cinemas with the files simply up-converted and it looked fantastic! In contrast to this, the Blackmagic camera shoots 2.4K before debayering and the Go Pro Hero 3 only shoots 4K images at 16 frames per second – so neither of these are in contention for a 4K level of acceptability.
www.vmi.tv
(JP/CD)
Solidmate Ltd Memory Card Hire London

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