Arri Alexa 16:9 vs 4:3 sensor

[Kasper Nystrom]

I am considering buying an Arri Alexa for my film company. Most of our project is filmed in 16:9 with normal spherical lenses, but I want to have a camera that can handle anamorphic lenses too.

So i am wondering if the Arri Alexa plus 4:3 is cropping in when you have it on 16:9 mode and shoot with spherical lenses, and i should therefore go with the Arri Alexa classic ev with the 16:9 sensor?

[Robin Phillips]

its a taller, 4 perf sized sensor

[David Mullen ASC]

It’s the same sensor, which is 1.54:1 full aperture, it’s just passed QC to allow the full height for 4x3 use.

[Kasper Nystrom]

Thank you for replying.

What do you mean with QC?

[David Mullen ASC]

Here is the sensor areas:

[David Mullen ASC]

“QC” meaning Quality Control. They build the wafers for these sensors and check them for dead pixels, etc. and some aren’t perfect from corner to corner but the area to be used for 1.78 is good, so it can be used for a 16x9 recording but not for Open Gate or 4:3 recording. But all the S35 Alexa sensors are the same physical size and shape, 1.54 : 1. 

[Kasper Nystrom]

Oh i see.

So same sensor size, but is it the same resolution?

I have heard some say that the Alexa classic has a 2.8k sensor, and the Alexa mini has a 3.2k sensor.

[David Mullen ASC]

It’s all the same 1:54 : 1 / 3.4K sensor in all the Alexas (except the LF and Alexa 65, which also use the same sensor but stitch two or three together) — it’s the Alev sensor. It’s just that some cameras allow you to record all of the sensor area and thus resolution. 2.8K is just a smaller width of the sensor than 3.2K or 3.4K. The original Alexa limited the width to 2.8K because that was the same width as Super-35 film and the rest of the sensor area could be used for lookaround in the viewfinder.

[Kasper Nystrom]

On 1/3/2020 at 10:04 PM, David Mullen ASC said:

It’s all the same 1:54 : 1 / 3.4K sensor in all the Alexas (except the LF and Alexa 65, which also use the same sensor but stitch two or three together) — it’s the Alev sensor. It’s just that some cameras allow you to record all of the sensor area and thus resolution. 2.8K is just a smaller width of the sensor than 3.2K or 3.4K. The original Alexa limited the width to 2.8K because that was the same width as Super-35 film and the rest of the sensor area could be used for lookaround in the viewfinder.

Is there any way to film in 3.2K or 3.4K with the Alexa Plus 4:3?
I feel it is a waste of pixels to not utilize all of the Alev sensor.

[David Mullen ASC]

I believe there was a software upgrade to the old Alexa Plus 4:3 to allow 3.2K ProRes and 3.4K Open Gate. Of course, you wouldn’t be recording a 4:3 image anymore at those resolutions since you’d be using more of the sensor’s width. As I keep saying, the overall sensor in all Alexa cameras are the same, 1.54 : 1, 3.4K. So 4:3 sits inside this, using the max height but cannot use the max width. So 4:3 is 2.8K wide.

There was an ad in our marketplace that mentions the options:

https://cinematography.com/index.php?/topic/81870-arri-alexa-plus-43-cinema-camera-for-anamorphic-or-169-13750/

[Ronald A Carrion]

why would someone buy a 4:3 when everybody is shooting 16:9?

[M Joel W]

29 minutes ago, Ronald A Carrion said:

why would someone buy a 4:3 when everybody is shooting 16:9?

The Witch for instance used the look around room to frame for 1.66:1 and some other indie movies have alternate aspect ratios, too. 

However, the main intent of the 4:3 license is to shoot anamorphic (4 perf frame resulting in a 2.66:1 image you can then crop to 2.4:1).

I believe the upgrade David is referring to also requires a hardware upgrade. I strongly suspect even the 16:9 Alexas would be 4:3 capable and are basically crippled.