Full-Frame Sensor Adds Resolution Without Altering Size of Photosites

ARRI announced the Alexa LF, a new camera with a large-format image sensor that can capture imagery at about 4.5K in open-gate mode, or at UHD resolution when shooting 16:9.

ARRI said the new sensor is really just a bigger version of the existing Alexa sensor, upscaled to 36.70×25.54mm, which is slightly larger than full frame. In Open Gate mode, the Alexa LF captures at a native resolution of 4448×3096. A 16:9 mode is tailor-made for capturing UHD footage at 3840×2160 (using a 31.68×17.82mm cut-out of the sensor) as well as downscaled ProRes 2K (2048×1152) or ProRes HD (1920×1080), while a 2.39:1 mode captures footage at 4448×1856 in the wider ‘scope aspect ratio.

Anamorphic shooters will use the Open Gate mode with full-frame lenses, while Super 35 lenses will require use of a 6:5 center portion of the 16:9 sensor mode, which must be cropped in post.

alexa-lf-1.jpg

“The larger Alexa LF sensor has the same optical pixel size as other Alexas, resulting in a 4448×3096 image,” said Marc Shipman-Mueller, ARRI’s product manager for camera systems, in a prepared statement. “This doesn’t just add definition, it creates a whole new look — one that is truly immersive, with a three-dimensional feel.”

ARRI rates the Alexa LF’s exposure latitude at 14+ stops and EI 800, and the camera has eight FSND filters that can be inserted manually, ranging from ND 0.3 to ND 2.4. ARRI’s wireless remote and video systems as well as Wi-FI connectivity are built into the camera. It weighs 17.2 lbs. (7.8 kg) and measures 14.33×7.91×6.22 in. (364x201x158 mm).

Shipments of the Alexa LF are expected to begin at the end of March, the company said.

It’s been a long wait for a 4K Alexa, with the company insisting, not unreasonably, that resolution is not the most important factor in determining overall picture quality, and many productions and cinematographers have happily made the Alexa their go-to camera despite competing systems that deliver more pixels. The position became less tenable as streaming services like Netflix and Amazon, eager to differentiate themselves from traditional broadcast and cable programming, began to insist on native 4K acquisition and delivery.

 The Alexa LF is closer in size to the Alexa SXT W than it is to the 6.5K Alexa 65.  ARRI

The Alexa LF is closer in size to the Alexa SXT W than it is to the 6.5K Alexa 65.
ARRI

The 6.5K Alexa 65 addressed the problem for some high-end projects, but with a much larger sensor and more demanding lensing and workflow requirements. The Alexa LF is smaller than the Alexa 65, but slightly bigger than the Alexa SXT W.

 Here’s how the Alexa LF’s different shooting modes break down in terms of sensor area, resolution, and maximum frame rates.  ARRI

Here’s how the Alexa LF’s different shooting modes break down in terms of sensor area, resolution, and maximum frame rates.
ARRI

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