Best Overall Image Quality | Technology

ARRI’s digital cameras produce exceptional image quality with the organic look and feel of film, delivering incredible production value at an affordable cost. Images created with any ALEXA or AMIRA camera contain all the ingredients for best overall image quality: high dynamic range, sharp and natural images, high sensitivity, natural color reproduction, excellent color separation, and the absence of artifacts.

To create such images, all components of the imaging chain are custom designed by our engineers and carefully tuned for optimal performance, starting with the optical low pass filter, the sensor, the imaging electronics, and the image processing software.

Film-like, Organic Look

Our cameras’ unique color processing was developed by the same ARRI color scientists that created the color science for the ARRILASER and ARRISCAN. Therefore, they are intimately familiar with the inner workings of film and digital image creation. The ALEV sensors render natural colors, great-looking skin tones, and show accurate color separation (important for greenscreen and other VFX work) while also demonstrating the ability to resolve mixed color temperature sources.

High Dynamic Range

ARRI digital cameras are equipped with one of two basic sensor designs: ALEV3 and ALEV4, both offering exceptional dynamic range. In both sensors, special consideration has been given to highlight treatment. Creating a good-looking roll-off in the highlights is probably one of the most difficult tasks for any sensor designer and we have spent enormous resources to ensure exceptional highlight handling. Both sensors’ wide exposure latitude translates into a “thick” digital negative; this means tremendous flexibility when color grading. The sensors' ability to retain definition, even when extremely under or overexposed, provides that extra bit of security in post.

The new ALEV4 sensor (used in ALEXA 35) has an unparalleled dynamic range of 17 stops (see our Whitepaper on Dynamic Range for more Information), providing greater flexibility and efficiency for the cinematographer on the set and the best basis for HDR projects in post.

The ALEV3 sensor design used in all other ARRI digital cameras offers 14.5 stops dynamic range, still more than any other digital camera can produce.

High Sensitivity

ALEXA's imaging system has been carefully designed to exhibit high sensitivity so filmmakers can create the kind of rich and spellbinding pictures that audiences associate with cinematic storytelling. The camera's sensitivity can be adjusted from EI 160 to EI 6400 (ALEV4) and EI 3200 (ALEV3) and it is able to maintain its high dynamic range at almost all sensitivity settings. The ALEXA 35 (ALEV4) is equipped with an optional “Enhanced Sensitivity” mode and optional “Shadow” ARRI Textures even lower noise when faced with the dark sets. Extremely low noise levels allow working with lower light levels, which opens new visual possibilities for fresh and unusual images.

Image Processing

ARRI's image processing philosophy is to maintain the highest quality possible throughout the entire processing chain. This means transporting and processing uncompressed 18 and 16-bit raw data inside the camera. This is a task that requires enormous processing power, which is provided by the latest in processor technology combined with a super-fast internal data bus. From this internal data stream, the image processing hardware derives various recording formats as well as the HD-SDI monitoring images and the viewfinder image.

REVEAL Color Science

ARRI’s discussions with filmmakers and a careful review of the image pipeline have led to significant image quality enhancements and a faster, easier workflow. REVEAL Color Science is a completely new image processing chain used by ALEXA 35 internally and available for ARRIRAW from ALEXA 35, ALEXA LF and ALEXA Mini LF in postproduction.

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Optical Low Pass Filter (OLPF)

The low pass filter blocks high image frequencies that would lead to artifacts when captured by the sensor. It is made from a modern, high-performance crystal with optical properties that have been fine-tuned for a perfect match between the transmitted image content and the sensor's photosite structure in the camera. The result is the creation of super sharp yet natural images.

IR and UV filters

ARRI cameras use a high-end infrared (IR) and ultraviolet (UV) filter, which are custom designed to block enough of the spectrum to avoid false color effects (as could otherwise be seen e.g. with dark synthetic materials) but that leaves enough of the near red spectrum to give skin tones a pleasant look. Designing the IR filter is a precarious balancing act, and the IR filters in ARRI cameras are also closely matched to the spectral response of the camera's sensor and the color processing in the camera for best skin tone reproduction.

FSND Filter Mechanism and Behind the Lens Filter

The AMIRA was the first camera to feature ARRI’s motorized FSND filter mechanism which is also used in ALEXA Mini, ALEXA 35, and bigger in size for ALEXA Mini LF. The ARRI FSND filter guarantees an even light reduction over the whole spectrum. Built into small filter frames in a motorized mechanism in front of the sensor, the FSND filter features three strengths that are available to dial in via the camera menu (0.6, 1.2, and 2.1 — plus optical clear. On ALEXA Mini LF and ALEXA 35: 0.6, 1.2, 1.8, and clear).

The ALEXA Classic camera series inherited the filter type in the form of a round “behind the lens filter” that sits magnetically secured in front of the sensor. For “matte box use” the same filters are also available as regular 4” x 5.65” and 6” x 6” filters.

Unencrypted, Uncompressed ARRIRAW

For the absolute best in image quality, for the greatest flexibility in post, and for safest archiving, the raw data from the sensor can be recorded as ARRIRAW files, an increasingly popular option used by feature films, drama series and commercials alike. ALEXA 35 images are processed in 18-bit linear space and recorded as 13-bit log ARRIRAW. Images from all other ARRI digital cameras are processed in 16-bit linear space and recorded as 12-bit log ARRIRAW. Image processing steps like de-bayer, white balance, sensitivity, up-sampling or down-sampling, which are irreversibly applied in-camera for compressed recording, SDI monitor outputs, and the viewfinder image, are not applied to ARRIRAW. All these parameters can be applied to the ARRIRAW image in post.

ARRIRAW is also an excellent future-proof archiving format. ARRIRAW is uncompressed and unencrypted, which means that anyone can access their ARRIRAW data with standard software tools in the future without any proprietary decryption or decompression. We openly publish our color science as standard SMPTE documents (Recommended Disclosure Document (RDD) 30:2014 and RDD 31:2014). The RDDs are available from the Society of Motion Picture & Television Engineers (SMPTE)'s website. A good example of the future-proof nature of ARRIRAW is the fact that ARRIRAW from ALEXA LF and ALEXA Mini LF can also be processed in post with the REVEAL Color Science that was introduced in 2022 with the ALEXA 35 and provides more accurate color rendering.

High Density Encoding

To cater the need for an efficient way to save time and storage without compromising image quality we’ve partnered up with CODEX who have developed a solution for lossless data encoding: High Density Encording, or HDE for short, is an encoding technique optimised for Bayer pattern images. ARRIRAW images encoded with HDE are approximately 60% of the original size. When an HDE file is decoded, it is a bit-for-bit perfect match to the original file. For more information have a look at the CODEX HDE website.

Compressed Recording, HD-SDI and the Viewfinder

While the creation of ARRIRAW inside the camera is relatively straightforward, the creation of color images for compressed recording, SDI monitoring, and the viewfinder is more complex, as the camera must process multiple streams of full color images from the raw image data in real time. Not only that, but the recorded image, the SDI outputs, and the viewfinder image can have different scaling, different looks, and different display color space settings. To achieve this, a powerful image processing engine debayers the raw image data, applies white balance and sensitivity, and re-samples or de-squeezes the images depending on the required recording and output formats.

The tremendous processing power for all those steps comes from our cameras’ image processing hardware, which consists of the latest generation of FPGAs (Field Programmable Gate Array). FPGAs are re-programmable digital processors. They not only have the horsepower to deliver multiple streams of the highest image quality, but their re-programmable nature ensures that improvements in processing can be made available to all existing cameras. This happened, for instance, with ALEXA Classic Software Update Packet 11, which provided a better de-bayering algorithm, instantly improving the image quality of all ALEXAs in the field.