ALEXA SXT / SXR Frequently Asked Questions

Welcome to the frequently asked questions about ALEXA SXT /SXR.

1. ALEXA Camera Line-up and Upgrades
  • ALEXA SXT EV, ALEXA SXT Plus and ALEXA SXT Studio replace the ALEXA XT cameras.
  • Due to the launch of ALEXA Mini, there will not be an ALEXA SXT M.
  • The original ALEXA remains in the program and gets re-named ‘ALEXA Classic EV’.
  • Until ALEXA SXT is available we will continue to sell ALEXA XT cameras.
  • The ALEXA Plus upgrades (ALEXA to ALEXA Plus and ALEXA XT to ALEXA XT Plus) remain in the program and are joined by the new ALEXA SXT EV to ALEXA SXT Plus upgrade.


In terms of hardware, the main electronics boards in ALEXA SXT cameras are new. These are the same high performance electronics boards as used in the ALEXA 65. Additionally, the left side cover containing the media bay is new. What has remained is the sensor: ALEXA SXT cameras have exactly the same sensor as the previous generations of ALEXA cameras, the 3.4K ALEV 3 sensor, that is the basis for the image quality of all ALEXA cameras.

In terms of software, the new image processing path and the pixel correction algorithm from the ALEXA 65 are being used, as well as color management and noise reduction from AMIRA. 
Here is an overview of all available ALEXA upgrades:

It is our philosophy to make sure that our customers have a functioning business model, so we try to make sure that those who recently bought a camera are not left in the dust. For ALEXA XT, ALEXA XT Plus and ALEXA XT Studio cameras shipped between January 1, 2015 and the first shipment of ALEXA SXT cameras, we offer a full SXT Upgrade for free. That camera will have the ‘ALEXA SXT’ name, all the features of a new ALEXA SXT camera and all the future upgrade potential. This offer is good for one year after first shipment of ALEXA SXT cameras. The upgrade has to be done by ARRI Service in Munich. This offer is not available for ALEXA XT M cameras, ALEXA Classic cameras or ALEXA Classic cameras with the XR Module upgrade. 
For ALEXA XT, ALEXA XT Plus and ALEXA XT Studio cameras shipped before January 1, 2015, we offer the SXR Module Upgrade. ‘SXR’ stands for Super Extended Recording and upgraded cameras will be called ‘ALEXA SXR’. The upgrade includes three new electronic boards and a new media bay. For now an ALEXA SXR will have the same features as ALEXA SXT cameras, but the future upgrade potential may be limited. This offer is not available for ALEXA XT M cameras, ALEXA Classic cameras or ALEXA Classic cameras with the XR Module upgrade.


First off, those who had bought a camera a while ago have already had the ability to make some money with the camera. And second, we also have to make some money to finance all that development, so we can’t extend an offer like that forever into the past. There has got to be a cut-off point that makes financial sense for our customers and for us, it is a precarious balance we are trying to achieve there. And third – we still have the SXR upgrade available to all XT cameras ever sold. 
When we build a new ALEXA SXT camera, we can build it with an eye on features that we want to include in the future. When we upgrade an existing XT camera to SXR, it would be cost prohibitive to make all those changes. We will of course try to make as many future improvements available to as many cameras as possible, but there is no guarantee the ALEXA SXR cameras will have all the future upgrade potential of the ALEXA SXT cameras. 
The ALEXA Mini fulfills most features of the ALEXA XT M. 
ALEXA SXT and SXR cameras do not have the option of recording DNxHD. If an XT camera to be upgraded to an SXR has a DNxHD license, the upgraded camera will not have the license anymore. 
The plan is to ship the first ALEXA SXT cameras around mid-2015. However, those camera will only be capable of recording ARRIRAW onto SXR Capture Drives with ALEXA SXT/SXR SUP 1.0. Support for ProRes, XR Capture Drives, CFast 2.0 cards, SxS PRO cards, SxS PRO+ cards and some new features will follow shortly there after with ALEXA SXT/SXR SUP 1.1. The ‘2015 ALEXA XT Special’ and the SXR upgrades are also planned to ship around mid-2015 and will be handled based upon availability of camera to be upgraded.

ALEXA SXT/SXR camera support the following media. Each media needs one of four new adapters.


As we like to have everything backwards compatible, using the existing adapters was our first design intention. However, since the SXR Capture Drives needed a new high speed connector, you can end up with more electrical interfaces than is good for signal integrity. So we chose one adapter for each media family, which combines the greatest flexibility with the best signal integrity.

3. ALEXA SXT/SXR Features

Here is the short list:


  • ProRes 4K recording
  • Improved image quality
  • New looks and smoother workflow (ASC CDL & 3D LUTs)
  • Three independent HD-SDI outputs
  • Faster, higher capacity SXR Capture Drives
As we like to have everything backwards compatible, using the existing adapters was our first design intention. However, since the SXR Capture Drives needed a new high speed connector, you can end up with more electrical interfaces than is good for signal integrity. So we chose one adapter for each media family, which combines the greatest flexibility with the best signal integrity.

And here is a slightly longer list with a little more detail:


  • Easy in-camera ProRes 4K recording
    • ProRes 4K UHD (3840 x 2160) recording format for 4K UHD TV deliverables
    • ProRes 4K Cine (4096 x 2636) recording format for 4C DCI cinema deliverables
  • Improved image quality
    • Completely overhauled image processing chain
    • Advanced pixel correction
    • Optional noise reduction
  • New color management
    • Matches current ALEXA images, but provides the basis for radically different looks
    • 3D Look-up Tables, ASC Color Decision List
    • Live in-camera grading on set
    • Rec 2020 gamma
    • Same tools for ALEXA SXT, ALEXA Mini & AMIRA
  • Super flexible on-set monitoring
    • Three fully independent HD-SDI outputs
  • Powerful new media bay
    • Supports new high speed SXR Capture Drives (1 TB or 2 TB) via SXR Adapter
    • Supports current XR Capture Drive 512 GB via XR Adapter
    • Supports SxS PRO and SxS PRO+ cards via SxS Adapter 2
    • Supports CFast 2.0 cards via CFast 2.0 Adapter 2


Some features of previous ALEXA cameras are not available in ALEXA SXT/SXR cameras anymore:


  • ALEXA SXT/SXR cameras do not have the option of recording DNxHD, since DNxHD was simply not very popular as a recording format.
  • ALEXA SXT/SXR cameras do not support the Fiber Remote option.
  • ALEXA SXT/SXR cameras do not support 8, 16 and 32 GB SxS PRO cards.
  • ALEXA SXT/SXR cameras do not support ALEXA Look Files with a 1D LUT. Instead, they use the new ARRI Look File 2 with ASC CDL and 3D LUT support.
  • ALEXA SXT/SXR cameras do not support the SUP 10/11 CDL server functionality. This functionality has been replaced by the new AFL-2 (CDL & 3D LUT) metadata capture.

4. Sensor Modes, Recording Formats, Distribution Formats
A sensor mode defines an aspect ratio, which defines the area on the sensor that is being captured. A recording format define what is being recorded in-camera in the file. So while a sensor mode defines a certain number of photosites on the sensor, those may be recorded straight or up or down-sampled to create the recording format. Adistribution format defines how the final product is delivered to the consumer. The contents in the recording format is often up or down-sampled, cropped, repositioned or rotated in post before it becomes the final distribution format.

An example: Choosing a 16:9 sensor mode on the ALEXA SXT allows the further choice of various recording formats. Choosing the 4K UHD recording format means that a 16:9 area from the sensor is read out, up-sampled in camera to a 4K UHD image and then recorded. In this case the recording format of 4K UHD is the same as the distribution format of 4K UHD. 

ALEXA SXT/SXR camera support four sensor modes, 16:9, 6:5, 4:3 and Open Gate. Below is a basic guide to those sensor modes and the most often used recording formats.

The 16:9 sensor mode is most often used for TV shows that need an HD or a 4K UHD deliverable. For the 16:9 HD recording format, 2.8K from the sensor are used. For the 16:9 4K UHD recording format, 3.2K from the sensor are used. The 16:9 2.8K sensor mode can also be used to derive a 16:9 2K Cine recording format.


The 6:5 sensor mode (formerly 4:3 Cropped also) is used exclusively for any shooting with anamorphic lenses. Since anamorphic lenses squeeze the 2.39:1 image by a factor of 2, the resulting area used on the sensor has a 1.195:1 aspect ratio, which is 6:5.


The 4:3 sensor mode is as tall but slight wider than 6:5. Shooting 4:3 has become popular for VFX heavy feature films in the 1.85:1 aspect ratio (dotted line). The area above and below the 1.85:1 image is used for placing VFX markers and/or for up/down repositioning.


Open Gate uses the full sensor area of the ALEXA camera. This format has become popular for those shooting feature films in 2.39:1 or 1.85:1. The extra area above and below the image is used for placing VFX markers or for up/down repositioning. The extra resolution provides the best result when up-sampling to a 4K Cine recording format.

The 4:3 aspect ratio was originally left over from the film days, and now has been put to good use by VFX-heavy feature films. Anamorphic lenses don’t actually need the full width of the 4:3 image; they squeeze the 2.39:1 image by a factor of 2, and the resulting area used on the sensor has a 1.195:1 aspect ratio, which is roughly 1.2:1, which is 6:5. When shooting with anamorphic lenses in 4:3 sensor mode, you always have to crop the extra area to the left and right of the image in post, an extra processing step that is avoided by shooting in 6:5.

In the ALEXA XT cameras with SUP 11 we have introduced this mode, however, there it was still called ‘4:3 Cropped’, but that is the same thing as the ALEXA SXT/SXR 6:5 sensor mode. 

We have a new online tool in the TOOLS section of the ALEXA web pages, the ARRI Lens Illumination Guide.

Every lens is brighter in the center than in the corners: that is called the lens illumination. To get a feeling for how lenses perform in Open Gate, you first choose a sensor mode and what framelines you want to check out. Then you choose a lens model, focal length, iris and focus setting, which are all parameters that affect lens illumination. The resulting image will show how the illumination falls off towards the corners and if you get vignetting. We have most ARRI lenses in there already, but the guys are still shooting, so we will add more lenses as time goes by. You can see the result right there on the screen or save the images as a JPEG file.

Some lenses do better and others worse. One of the lenses that does really well (even though it is not in yet) is our Ultra Wide Zoom UWZ 9.5 – 18; it was designed for a large image circle. Most primes under 18 mm have an issue shooting Open Gate, so the UWZ really solves the question of how to shoot wide angle with Open Gate.

ALEXA SXT/SXR cameras can record ARRIRAW just like the XT cameras could: 16:9 ARRIRAW up to 120 fps, 6:5 ARRIRAW up to 90 fps, 4:3 ARRIRAW up to 96 fps and Open Gate ARRIRAW up to 75 fps.

ALEXA SXT/SXR cameras can record ProRes in HD, 2K Cine, 3.2K, 4K UHD or 4K Cine. And they can do that with all high-end ProRes flavors from ProRes 422 to ProRes 4444 XQ.

In addition, we are working on a number of improvements and new recording formats, which we will announce once all tests have been concluded to our satisfaction. 

ProRes 3.2K is a recording format we already have in ALEXA XT cameras with SUP 11. We are seeing some productions that shoot ProRes 3.2K and do a post up-sample to 4K UHD. But we are also seeing some productions shooting ProRes 3.2K when they want an HD or 2K deliverable. The 3.2K gives them extra space around their image for resizing, reframing, rotating or stabilizing. In fact, in our online ARRI Frameline Composer we now have a preset for exactly that purpose, called ‘1.78:1, 2.8K inside 3.2K’. You can find the Frameline Composer in the TOOLS section of the ALEXA web pages, it is a great tool for making your own framelines.

5. ProRes 4K
ALEXA SXT/SXR cameras use the extra horse power of the ALEXA 65 electronics to perform a mild up-sample in-camera, either to ProRes 4K UHD or to ProRes 4K Cine. The number of photosites are only one of many parameters that form a quality 4k image. The combination of ALEXA’s best image overall image quality with the new processing chain and the relatively small up-sample factor of 1.2x preserves the fundamental qualities of the ALEXA picture that filmmakers so love.  

The short answer is that our understanding of what is important to create a good looking image has changed, technology has advanced and the ALEXA overall image quality is so good, that it up-samples beautifully.


Here is the long answer:
Scientifically, if you want the best resolution of a black and white test chart, you should over-sample, i.e. have more photosites on the sensor than in your recording format. However, an image is not just resolution and, if I may quote Rodney Charters here, movie making is not a science project. Some people talk as if all a cinematographer does all day is shoot black and white charts, and resolution is the most important image quality parameter. But that is not the case, and in fact there is so much more to it that it is crazy to look at just one aspect of the image, i.e. resolution, and make all decisions based on that. Parameters like dynamic range, noise, skin tone reproduction and the quality of the debayer are actually much more important than just resolution.

And the technology has changed. Debayering has gotten much, much better, the electronics are much more powerful and we have learned a lot about in-camera image processing and up-sample algorithms. We have a whole color science department that continually pushes the envelope of what is possible, and that is very, very important. They came up with our in-camera up-sample algorithm which is just fantastic.

So at some point we entertained the idea to do this mild up-sample from 3.2K photosites on the sensor to 3.8K (=  4K UHD) pixels in the file. And there were many inside ARRI who were opposed to that. But we have learned that the theory will only get you so far and at some point the only way to really know is to shoot a test. And the results looked great. In fact, we compared it to some ‘native’ 4K images from other cameras and our up-sampled images looked as good, if not better. That convinced everybody within ARRI that it’s possible to do a mild up-sample of 1.2x and still get the beautiful images everyone is used to from ALEXA. Now we have an answer for those who need to record a 4K image, be that in 4K UHD or 4K Cine.

The ProRes 4K UHD recording format (3840 x 2160, 16:9) is designed for a 4K UHD TV distribution format (3840 x 2160, 16:9). ProRes 4K UHD is derived from 3200 x 1800 photosites on the sensor in 16:9 sensor mode. These are the same values as used in AMIRA and ALEXA Mini.

The ProRes 4K Cine recording format (4096 x 2636, 1.55:1) is designed for the 4K DCI cinema distribution format container (4096 x 2160, 1.9:1). ProRes 4K Cine is derived from 3414 x 2198 photosites on the sensor in Open Gate sensor mode. ProRes 4K Cine is unique to the ALEXA SXT/SXR cameras in ARRI’s line of cameras.

Both formats use the same high quality 1.2x up-sample filter.

The 4K Cine recording format contains 4096 x 2636 pixels, which is 477 lines more than the 4K DCI distribution container (4096 x 2160). This extra area above and below the image is designed for up/down image repositioning or placing of VFX markers. This is an example where the recording format purposefully contains more than is needed in the distribution format to provide for some added flexibility in post. 

6. Current and Future ALEXA Sensors
First, we don’t think that Moore’s Law is applicable to sensor design.

Second, the photosite design of the ALEV 3 sensor is unique. That design provides the great dynamic range and the highlight handling that the ALEXA has, it provides the sensitivity, the low-noise floor and the beautiful skin tones. This sensor design combined with the ever improving processing chain has stood the test of time. So far we have not seen any camera that comes close, so we think we have a really unique piece of technology here

Of course we are working on a new sensor, we are a camera manufacturer. However, we’re only going to release it in a product if we can achieve better overall image quality as ALEXA. And the image quality of the ALEXA is really hard to beat, even for us. The ALEXA SXT is a fantastic piece of gear with many new options tailored for today’s professional productions. 

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Amira Models

Discontinued Models

Alexa Camera Overview


ALEXA XT Software Update 11.0

ALEXA Frameline Composer

ALEXA Software Update 11.0

ARRIRAWConverter Tutorials