Today Arri announced that they will offer a new software upgrade for the AMIRA, which will allow it to record ProRes Ultra HD files (at a resolution of 3840×2160). The upgrade is expected to be available for purchase at the online Arri License Shop by the end of 2014. Many people have been waiting for a 4K solution from Arri, and now the AMIRA will offer support for those who need to deliver in higher-resolution formats. The AMIRA can already record in HD and 2K formats, but with this new upgrade it will up-sample the sensor into an Ultra HD format.
Actually, Arri has always over-sampled their HD picture in the camera. In the original ALEXA, 16:9 HD content is sampled from 2880×1620 photosites.
This holds true for the AMIRA, but it turns out that the camera offers more area of the sensor to sample. When recording in UHD mode, the AMIRA will sample a 3200×1800 photosite area on the sensor, which is both wider and taller than the area used for HD recording. The extra pixels allows for a better up-scale of only 1.2x to Ultra HD. This is similar to working with Open Gate RAW footage from the ALEXA XT, except this up-sample to UHD happens in camera, and in real time. This new update helps position the AMIRA for the many productions that are now requiring Ultra HD recording.
Make sure to check out the official announcement on Arri’s website.
EDIT: Arri has also announced a 3.2K ProRes mode for the ALEXA, due out in early 2015. While the AMIRA up-samples from 3.2K to UHD in camera, the ALEXA will directly record the 3.2K file, allowing for any up-sampling to UHD in post production. The official announcement can be found here.