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How to Shoot Open Gate 4:3 on the ARRI Alexa Mini

The ARRI Alexa Mini is one of the few cameras out in the world today that natively desqueezes anamorphic lenses. Its tall and boxy ALEV III sensor is perfect for the job of capturing the anamorphic experience, both in ProRes and in ARRIRAW. 

1 - Pulling your HW Info

First step is to purchase a license for the privilege of shooting 4:3. But before you can even begin the purchase process, you have to pull some data from your Alexa Mini - essentially its thumbprint - to verify the thing. To get this thumbprint, plug a flash drive formatted as FAT32 into the camera via the USB port directly below the CFAST slot in the back. Then navigate to Menu>Media>Prepare USB Medium and select Confirm. This should give you a message declaring the process a success when it finishes. 

With that completed, navigate to Menu > System > Licensed features, then press HW INFO. Press confirm on the next screen, and voila - it has been saved to the flash drive under  ARRI /ARRI Mini /LICENSES. You will need this for step two, so remove the drive from your camera and plug it into your computer.

2 - Purchasing the License

If you couldn’t guess, the next step is heading over to the ARRI License Shop, where you can buy the ability to shoot Open Gate 4:3. They will ask for the serial number of your camera, which is then burned into the license directly. This is a non-transferable piece of software, unfortunately.

Follow their instructions, then copy the downloaded files to ARRI /ARRI Mini /LICENSES on the USB drive again. Move the USB drive back over to the camera, then open Menu > System > Licensed features. Press Add, scroll to your 4:3 license, and confirm your selection to install. When the install is complete, reboot your camera to seal the deal. 

4 - Recording in ProRes

The 4:3 license has allowed you access to a plethora of new settings, all listed as simple resolution choices. While they are not true Open Gate, they are pretty darn close and more than enough for any anamorphic workflow. Those choices are:

* 4:3 2.8K (2880 x 2160) 

* 2.39:1 2K Ana. (2048 x 858 de-squeezed from 2560 x 2145) 

* HD Ana. (1920 x 1080 de-squeezed from 1920 x 2160) 

One thing to keep in mind is that shooting anything less than 4:3 2.8K in ProRes essentially throws away every other pixel. This can save processor power and allow for higher frame rates. But if you want to preserve maximum resolution and image quality…

5 - Recording in ARRIRAW

The ARRIRAW license, when combined with the 4:3 license, unlocks a few extra goodies. With both installed, the Alexa Mini can record Open Gate 3.4K RAW - utilizing the entire ALEV III sensor, top to bottom. In all other record modes, the camera is recording from some subset of all the pixels available to it. In Open Gate, every single pixel is active. This is great for shooting squished anamorphic images, which can certainly be de-squeezed through the viewing path to your EVF or monitor. But no matter whether you go with ARRIRAW or ProRes, you are still getting one of the best digital anamorphic images money can buy.