ARRI ALEXA XT Getting Internal 3.2K ProRes Mode for Upscaling to 4K

ARRI ALEXA XT 3.2K ProRes for UHD-4K
Just a week after announcing that the ARRI AMIRA would get an internal 3840 x 2160 UHD ProRes mode, ARRI is now saying that its higher-end ALEXA XT cameras will be getting an internal 3.2K ProRes recording mode designed to be either downscaled to 2K/1080p, or upscaled to UHD, or even 4K, in post.

While these cameras are already capable of Open Gate mode, which uses the entire 4:3 3.4K sensor to record RAW, this new mode is 16:9 only, similar to the recording area of the AMIRA UHD mode. The difference is that the ALEXA won't be doing any upscaling inside the camera — they'll be leaving that for you to do in post. The 3.2K mode is likely somewhere around 3200 x 1800 (possibly higher), to give the upscaler cleaner numbers to work with (AMIRA would start in the same place, but upscales to 3840 x 2160 internally)

Here is ARRI on the new 3.2K ProRes recording mode:

The camera's stellar overall image quality in combination with ProRes 3.2K (due for release as a software update in early 2015) and ARRIRAW Open Gate (released earlier this year) allows for simple up-sampling to UHD or 4K in a quality at least as good as other contenders. And because of their unequalled exposure latitude and highlight handling, ALEXA images are already uniquely HDR-compatible. Put simply, ALEXA remains the safest available capture tool for asset longevity, no matter what future standards come to fruition.

ARRI ALEXA XT is Future Proof Recording Modes

And more here:

For TV productions looking for a UHD deliverable, ALEXA XT cameras and ALEXA Classic cameras with the XR Module upgrade offer the new and cost-efficient ProRes 3.2K recording option. At data rates far below uncompressed ARRIRAW, ProRes 3.2K provides the benefits of the well-established and efficient ProRes workflow. As an additional benefit, most lenses fully cover the 3.2K image circle that results from the 16:9 ProRes 3.2K image. A straightforward up-sample from ProRes 3.2K using standard post tools delivers UHD images of the highest quality for broadband and broadcast.  

So ARRI is very much recommending upscaling as an option to get 4K/UHD footage from their cameras that record below that resolution. It's an interesting development, especially since there was a huge outcry about cameras like RED early on not shooting "real" 4K since each pixel does not contain all of the color information necessary for a complete picture, it has to be Debayered in post to get an image that makes sense, and resolved detail is lost along the way. Shooting 4K nets you lower than 4K resolution, somewhere around 3.2K, depending on the algorithm. So with that said, shooting at 3.2K is probably resolving somewhere around 2.5K, which is obviously nowhere near 4K. This is why single-sensor cameras wanting the highest fidelity have always started with recording more resolution for later (like ARRI's original 2.8K mode for 2K/1080p). The Sony F35 was a 5K sensor just for 1080p. The Sony F65 has an 8K by 2K sensor for a 4K output. RED's DRAGON is 6K. Oversampling is to get around the bayer pattern and start with more information:

Bayer Pattern Interpolation
Credit: Solimac Automation

Numbers don't tell the whole story, however. ALEXA footage has been upscaled to 4K plenty of times with good results, and even blown up to IMAX. A good upscaling algorithm should be able to get a lot out of the footage, though it's not really possible to get more actual detail than the resolution you're shooting. You can certainly give the appearance of more detail with more contrast or sharpening, but this solution from ARRI is more of a stopgap for users looking to get more detail and more pixels out of their master file until the company moves to 4K and higher sensors. 

In the end, it's all about what it looks like. You've probably already seen ARRI footage upscaled to 4K and shown in a theater, and if you weren't complaining, the upscalers have done their job. ARRI's dynamic range and color are both excellent, and that goes a long way towards getting a pleasing image. If one camera is higher resolution, but another camera's image actually looks better, the number of pixels isn't telling the whole story.

3.2K ProRes will be a software update in early 2015, so we won't have too long to wait before we see how this will work in practice.     

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Your Comment



September 4, 2014 at 12:44AM, Edited September 4, 8:56AM


In a world of camera after camera review, and montage after boring montage attached to another boring time-lapse, Alexa can always make one frame worth a thousand montages. Yes I love me some Alexa.

September 4, 2014 at 12:44AM, Edited September 4, 8:56AM

John Wilton


September 4, 2014 at 1:27AM, Edited September 4, 8:56AM


That's just how people from Boston say 4K...

September 4, 2014 at 1:33AM, Edited September 4, 8:56AM

Joe Marine
Camera Department

XT costs $ 120,000 !!
but that sucks !!!
I love Arri, but this is horrible. I do not like it.
Everything is confused.This is not a true 4K.

September 4, 2014 at 3:46AM, Edited September 4, 8:56AM


How exactly would you describe "true 4K"? None of the 4K cameras shoot true pixel to pixel 4K.

September 4, 2014 at 9:31PM, Edited September 4, 9:31PM


I once saw a little indie movie called Avatar, hundreds of people left the theatre because it was not true Imax...

September 4, 2014 at 4:42AM, Edited September 4, 8:56AM


It's stop gap measure till they finish their 4k sensor. All the touting of 4 k not being needed have fallen on deaf ears ..... It's where everything is going or has gone at this stage .... They HAVE. To jump on. But when they give you 4k ..... I can't wat to see it.

Question tho. Kinefinity cameras seem to be quite good ..... Anyone knows ther reason they can't get licenses to codecs like prores or DNXHD ? Is it that collectively they don't want china in or did Kinefinity (borrow/steal) an idea or something? Cuz the Kinemini seems like a good buy at 3k USD

September 4, 2014 at 4:47AM, Edited September 4, 8:56AM


Actually in feature film and television the Alexa is the top camera, so in truth 4K is not that big of a deal in high end production.

Its likely Kinefinity either cannot afford or does not want to pay Apple and Avid for the licenses to ProRes or DNXHD.

September 4, 2014 at 9:37PM


This is exactly right. And basically what I've found is that these blockbuster action movies use RED because they're so much smaller and can be rigged up small to be able to move quickly through complex camera moves. For films with less action, the more "Oscar-y" ones, they almost always use Alexa. Look at the statue haul for Birdman this year. Shot on Alexa. I saw two movies within a single week, one shot on RED and one shot on Alexa, and I thought the Alexa one looked better. Now to be fair the Alexa film was DP'ed by Roger Deakins and he's a master, but still.

March 10, 2015 at 6:49PM


It's nice to see Arri moving towards 4k. The AMIRA 4k upscale sounds kind of disappointing. I wonder if it'll actually make a difference.

September 4, 2014 at 7:50PM, Edited September 4, 7:50PM

Zachary Will

The HD television you are watching at home is upscaled. US television is broadcast in 720P and upscaled to 1080i.

People don't seem to notice or complain.

September 4, 2014 at 10:20PM


You know the image is robust when you can upscale it to imax

September 4, 2014 at 9:33PM, Edited September 4, 9:33PM

Alex Smith

4K does not make up for low bit rates or chroma subsampling. All of these cameras are recording 4K very differently.

The Alexa is shooting 4K UHD which is (3840×2160) from a 3168 x 1720 (35mm) sized sensor. ProRes 4444 12bit

Red One Mysterium-X is shooting 4K DCI (4096×2160) from a 4480 x 2304 (35mm) sized sensor. Redcode 4444 12 bit

Panasonic GH4 is shooting 4K DCI 4096×2160 from a 4608x3456 (micro four thirds) sized sensor. MPG4 422 8 bit

Black Magic Cinema is shooting 4K UHD (3840×2160) from a 3840 x 2160 (35mm) sized sensor, ProRes 422 10 bit

September 4, 2014 at 9:40PM


That's nice, but what do these numbers mean? I've seen great films from no budget to multi billion budget shot on all these cameras. It's about the person behind the camera, not the stupid crap inside.

March 10, 2015 at 6:51PM


Seems to confirm the speculation that the sony F55 was heavily rented because of its 4k in detriment to the alexa. Arri had to respond well I guess by next year NAB they would show their 6k camera.

September 4, 2014 at 11:50PM

Director of photography

4 week ago I sold our Arri Alexa Classic in the hope our new SXT would arrive. Over the past 4 weeks I have been renting a Sony F55 and getting some very good results except for the usual Sony skin tones. Today I took delivery of our new Alexa XT Plus and I have to say it's very disappointing on the resolution side at 3.4k up scaling to UHD for reframing in post. Why is no one complaining about the whereabouts of the SXT? I have to say we own a fair amount of Arri product and the way Arri have handled the SXT thing may prove to be our last Arri purchase.
Forever hopeful.

April 19, 2016 at 3:20AM, Edited April 19, 3:20AM

Dave Ellis
Director / DOP