The Arri Alexa (stylised as ALEXA) is a film-style digital motion picture camera system made by Arri first introduced in April 2010. The camera marks Arri's first major transition into digital cinematography after smaller previous efforts such as the Arriflex D-20 and D-21. It features modularity, PL mount lenses, a Super 35 sized CMOS sensor shooting up to 2880×2160 resolution and supports uncompressed video or proprietary raw (ARRIRAW) data.
The camera is equipped with an onboard SxS card encoder that can record in either Rec. 709 or Log-C to ProRes 422 or ProRes 444 codecs. as well as DNxHD in 1080p resolution. For an additional 1,350 Euros, Alexa camera owners can purchase a software "key" that will unlock the camera's ability to record up to 120fps in ProRes 422 HQ.
The camera is designed for use in high budget feature films, television shows, and commercials, and is widely seen as Arri's answer to the growing acceptance of the Red One camera, along with lower resolution cameras like the Sony CineAlta (35 mm, 1080p), Panavision Genesis (35 mm, 1080p), Thomson Viper FilmStream (2/3", 1080p) to shoot feature films.
The range of models has been expanded through the camera's lifetime. In 2012, there were five basic models of the Alexa:
The first camera of the Alexa product family. Introduced in April 2010.
The ALEXA Plus adds integrated wireless remote control, the ARRI Lens Data System (LDS), additional outputs, lens synchronization for 3D, and built-in position and motion sensors.
Alexa Plus 4:3
The ALEXA Plus adds integrated wireless remote control, the ARRI Lens Data System (LDS), additional outputs, lens synchronization for 3D, and built-in position and motion sensors and a 4:3 sensor making it ideal for anamorphic cinematography.
The Alexa M has its imaging and processing unit broken down in two parts to be small, compact and lightweight for 3D rigs and other uses where size is a concern.
The Alexa Studio features an optical viewfinder, mechanical shutter, and a 4:3 sensor making it ideal for anamorphic cinematography.
In February 2013, the range was renewed as Alexa XT (XT standing for extended technology). This range is upgraded versions of the original Alexa cameras, which are equipped with a so-called XR module, which replaces the SxS module on the cameras, and allows direct RAW recording without the need for an external recorder. This module records on dedicated SSD drives. Further improvements are an internal ND filter unit, a 4:3 sensor and a quieter cooling fan. The range accordingly comprises the Alexa, the Alexa XT, the Alexa XT M, the Alexa XT Plus, the Alexa XT Studio, and the Alexa Fiber Remote. Existing cameras can be upgraded with the XR module for internal RAW recording.
On 21 September 2014 at the Cinec convention in Munich, Arri announced the Alexa65, a 65mm digital cinema camera. The camera will be available for rental only, like those from competitor Panavision. Arri announced details of the camera on their Arri Rental Group website:
At the heart of the ALEXA 65 is the A3X sensor; the largest high-performance motion picture sensor available on the market today. The sensor has a 54.12 mm x 25.59 mm active imaging area, which is even larger than the film gate of ARRI’s 765 65 mm film camera.—ARRI Rental Group, arrirentalgroup.com
The camera was recently used to shoot IMAX sequences for Mission Impossible - Rogue Nation.
In May of 2015, Marvel Studios announced that the two-part Avengers: Infinity War would be shot using a version of the camera built in collaboration with IMAX, marking the first time a full-length theatrical film will be shot entirely in IMAX. 
On 24 February 2015 Arri announced the Alexa Mini. It has the same sensor as the other Alexa cameras. It features in-camera recording to CFast 2.0 cards, 200 FPS and 4K UHD in-camera upscaling.
On 18 March 2015, Arri announced the SXT line of Arri Alexa cameras which will support in-camera upscaling of Apple ProRes to 4K resolution and Rec. 2020 color space. Arri also announced the SXR module which can upgrade XT, XT Plus, and XT Studio cameras with the SXT features.
The Alexa's ALEV III sensor has 3392×2200 effective pixels used for generating an image, 2880×2160 pixels are generally used for recording on the Alexa Studio and M in 4:3 mode, and 2880×1620 pixels are used for recording on the regular Alexa and other models in 16:9 mode, the rest of sensor is used for lookaround in the viewfinder. Alternately the full sensor resolution may be employed in 'Open Gate' mode for resolution demanding situations.
The Arri Alexa can record to 1920×1080 ProRes 422 or ProRes 4444 on SxS Cards or 2880×1620 ARRIRAW to external recording devices. The Arri Alexa Firmware 7 increases the resolution on the SxS cards to 2k ProRes 4444 (previously 1080p)
ArriRaw is a raw codec similar to CinemaDNG that contains unaltered Bayer sensor information, the data stream from the camera can be recorded via T-link with certified recorders like those from Codex Digital or Cineflow.
The ArriRaw format (along with the other recordable formats) contains static and dynamic metadata. These are stored in the header of the file and can be extracted with the free web tool metavisor or with the application Meta Extract provided by Arri. Of particular importance for visual effects are the lens metadata, which are stored only when Arri's lens data system (LDS) is supported by the lens used.
According to cinematographer Roger Deakins, the Alexa's tonal range, color space and latitude exceed the capabilities of film. "This camera has brought us to a point where digital is simply better", says Deakins. Deakins used the camera to shoot the James Bond film Skyfall.
- "ARRIRAW | ARRI Digital". Arri. 15 July 2010. Retrieved 7 December 2011.
- Strauss, Will (7 April 2010). "Alexa to capture native QuickTime files". Broadcastnow. Archived from the original on 23 April 2010. Retrieved 9 April 2010.
- "ALEXIA product updates". Arri.
- "ARRI Group: News". Arri.com. Retrieved 2014-02-05.
- "ARRI Group: Cameras". Arri.com. Retrieved 2014-02-05.
- Renée, V. "Rumor No More: ARRI Reveals Their 6K 65mm Cinema Camera, the ALEXA 65". No Film School. Retrieved 22 September 2014.
- Deborah D. McAdams (2015-03-18). "Arri Rolls Out Alexa With 4K ProRes Recording". TVTechnology. Retrieved 2015-03-19.
- "ALEXA SXT". Arri. Retrieved 2015-03-19.
- metavisor - Free browser viewer for Arri Raw metadata
- American Cinematographer: Time Bandit. The ASC. Retrieved 7 June 2012.
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