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The ARRI ALEXA Classic is a genuinely iconic cinema camera.
It was used to shoot films including Drive, Arrival and Moonlight, yet today, the camera can sometimes be found for around $5,000. That puts the unmistakable ALEXA image within reach of filmmakers who could never have justified owning one when it was first released.
The colour, dynamic range and highlight roll-off still hold up remarkably well. But in a world increasingly dominated by full-frame cinema cameras, the ALEXA Classic’s Super 35 sensor can sometimes feel as though it has been left behind.
So we set out to change that.
The Reduxa A1 is a 0.71x focal reducer and interchangeable mount system designed for the ARRI ALEXA Classic, XT and SXT. Its purpose is to give these cameras a wider field of view, an extra stop of light and a more full-frame style of rendering, while retaining the image quality that made the ALEXA famous.
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The ALEXA Needed More Than a Focal Reducer
RED DSMC cameras are modular by design. Their lens mounts can be removed and replaced quickly, with the camera already providing support for multiple lens systems. The ALEXA Classic is different. Although its mount can technically be changed, the camera was primarily designed around PL lenses. Swapping mounts is comparatively slow and fiddly - not something most camera crews would want to do regularly on set.
We needed to create a complete mount system: one that would not only introduce focal reduction, but also modernise the front end of the camera and address some of the limitations of its original lens-mount design. That decision significantly expanded the project, but it has also led to a much more capable product.
The First Prototype
As far as we are aware, this was the first time a full-frame focal reducer had been used successfully on an ARRI ALEXA Classic.
So, How well would the optic perform on the ALEXA sensor?
It was an early development unit and far more limited than the final product. It did not contain the complete electronics, firmware or mechanical design we are now developing. But optically, it allowed us to test the part that mattered most. The ALEXA has always paired well with a wide range of lenses, partly because of the relatively thin optical stack positioned in front of its sensor. That characteristic works particularly well with our focal-reducer design.
In our studio tests, we were able to shoot wide open at approximately a T1 equivalent while retaining strong sharpness into the corners of the frame. More importantly, the prototype produced the wider, more dimensional rendering that many filmmakers associate with full-frame cinematography.
What a 0.71x Focal Reducer Actually Does
A focal reducer takes the larger image circle produced by a full-frame lens and concentrates it onto the ALEXA’s smaller Super 35 sensor. This has two major effects.
First, it widens the field of view. A 50mm lens used with a 0.71x focal reducer produces a field of view close to that of a 35mm lens:
50mm × 0.71 = 35.5mm
Second, concentrating the larger image circle onto the smaller sensor increases the amount of light reaching it. This produces approximately one additional stop of light. A 28mm F1.4 lens, for example, behaves approximately like a 20mm F1.0 when used through the reducer. That does not physically change the lens itself. Instead, the reducer changes how the lens’s image is projected onto the sensor, giving the camera a wider field of view and greater effective sensitivity.
An ALEXA With Almost Too Much Light
One of the most enjoyable discoveries during our test shoot was just how sensitive the ALEXA became.
Much of the footage was captured at dusk - a situation in which filmmakers would normally be fighting to maintain exposure. With the Reduxa prototype, we had the opposite problem. At approximately a T1.5 equivalent, the system was gathering so much light that we found ourselves trying to remove it.
One shot was captured with the ALEXA rated at ISO 160, its lowest available setting, while using five stops of neutral-density filtration. The result was an exceptionally clean image, with full shadows and almost no visible noise. As the ambient light continued to fall, we could gradually reduce the ND rather than changing the aperture, shutter or overall character of the image.
It was a very nice problem to have.
Comparing Super 35 and Reduxa Rendering
For another test, we filmed the artist Minnie in her studio. We captured one shot using a Sigma 35mm lens at T2, mounted directly onto the camera without focal reduction.
We then captured a second shot using a Sigma 50mm lens, also at T2, through the 0.71x Reduxa prototype. Because 50mm multiplied by 0.71 is almost exactly 35mm, the two setups produced closely matched framing. The camera and subject remained fixed between the shots.
At first glance, the difference can appear subtle. But when the images are viewed directly alongside one another, the change becomes much more significant. The standard image has the classic ALEXA appearance, with excellent colour straight out of camera using ARRI’s Rec.709 LUT. However, compared directly with the Reduxa frame, it feels slightly flatter.
The Reduxa image has a greater sense of depth. Minnie’s face appears more sculpted and lifelike, with a subtle three-dimensional quality that is difficult to describe but immediately apparent when the shots are placed side by side. We have also noticed that the Reduxa appears to help certain lenses resolve with greater clarity, particularly towards the centre of the image. The focal-reducer footage can look naturally sharper than the equivalent image captured without it.
We want to test this across a much wider selection of lenses before making any definitive claims, but it has been a consistent observation during our development work so far.
Building an Interchangeable Mount System
Our early prototype also included a basic version of the Reduxa adapter plate. The plate remains attached to the front of the camera and allows the primary lens mount to be removed by undoing four screws. This means the operator can move between an optical focal-reducer mount and a non-reducing pass-through mount without repeatedly dismantling the camera’s original front assembly.
In the final system, the adapter plate will also convert the ALEXA’s existing electronic connections into a pogo-pin interface. The goal is to make changing lens systems on the ALEXA Classic, XT and SXT feel much closer to changing mounts on a modern modular cinema camera.
Electronic communication is a major part of what we are developing, particularly in relation to lens control and integration with the camera. We will be explaining much more about that side of the project in a future update.
Where the Final Product Is Now
The unit shown in our initial test footage is an early proof-of-concept prototype. The current Reduxa A1 is significantly further along. Behind the scenes, we have been developing the firmware, electronics, hardware and mechanical design required to turn the optical prototype into a complete production system. There is a substantial software and electronics component to the project, particularly around aperture control, lens communication, optical calibration and integration with the ALEXA Classic platform.
Follow the Development of the Reduxa A1
We will be sharing much more about the Reduxa A1 as development continues, including further test footage, technical details and information about how we plan to launch the product. The best place to receive the latest announcements is through the CINELUX newsletter.
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