September 07, 2014

Arri shoots for Ultra HD + 4K

Users of Arri’s Alexa and Amira cameras will be able to deliver Ultra HD and 4K despite the cameras not having UHD sensors, thanks to up-sampling.

The documentary-style Amira will be upgraded to recording Ultra HD at up to 60 frames per second, in real time, via a paid firmware update due later this year, while ProRes 3.2K, a new recording format that allows easy up sampling in post to Ultra HD, will be available for the Alexa in a software update early next year. The Arriraw Open Gate format already allows this up sampling for 4K cinema.

Indeed, the Alexa has been proven to deliver the image quality needed for 4K or even Imax theatrical releases of such films such as Gravity, Maleficent and Iron Man 3, via post-production up-sampling. However, this isn’t really suitable for the fast-turnaround or lower-budget documentaries that the Amira would be used for.

Fortunately, the Amira will be able to record all ProRes codecs in UHD (3840x2160) directly onto the in-camera CFast 2.0 cards in real time under what Arri promises will be “an affordable software license (and a sensor calibration for existing Amiras)”. The upgrade is in response to feedback from Amira customers who were being asked about 4K deliverables by clients.

The Amira’s UHD output uses the same efficient 1.2x up-sample filter that allows Alexa’s Open Gate mode to optimize image performance for 4K, but will take place in camera in real time.

Wildlife cinematographer Rolf Steinmann, who was nominated for an Emmy this year for his work with Alexa on the BBC’s Wild Arabia, is currently using his Amira on a movie for Disney Nature. “For cameramen like me who own their gear, the UHD upgrade is a great way to stay future proof. From now on when there's pressure from the production side to deliver UHD, I can continue to work with Amira and won't have to compromise on image quality or on the camera's robustness and reliability,” he said.

Although Arri believes that “widespread adoption of UHD/4K post workflows, as well as availability of UHD displays in consumer homes and 4K projection in movie theatres is at least one to two years away – even in the most progressive markets,” it has seen that filmmakers are concerned about protecting their work for future developments. The possibilities of high dynamic range (HDR) displays, which it maintains “have an even greater effect on viewing experience than higher spatial resolution,” also have to be considered.

“Alexa can easily accommodate productions that choose to follow a UHD or 4K workflow. The camera's stellar overall image quality in combination with ProRes 3.2K or Arriraw Open Gate allows for simple up sampling to UHD or 4K in a quality at least as good as other contenders,” insisted Alexa product manager Marc Shipman-Mueller. “Because of their unequalled exposure latitude and highlight handling, Alexa images are already uniquely HDR-compatible,” he claimed.

Both the Alexa XT and Alexa Classic (with XR Module upgrade) will offer the ProRes 3.2K recording at data rates far below uncompressed Arriraw. Most lenses already fully cover the 3.2K image circle that results from the 16:9 ProRes 3.2K image.

Some movies (such as the most recent Bond instalment, Skyfall) have been shot in Arriraw 2.8K and up sampled successfully to 4K DCP, but Arriraw Open Gate, which was introduced for the Alexa XT earlier this year, records the full 3.4K sensor area for improved up-sample in post, and is in use already, on: Warcraft; San Andreas; Pixels; Goosebumps; and Sicario. Other features are shooting Arriraw 16:9 or Arriraw 4:3 and using Open Gate for VFX shots, including Terminator: Genesis, Fantastic 4, Agent 47 and Deus Ex Machina.

By David Fox

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