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Raw Files

Technical Notes 8k

SONY ALPHA RAW - From the Sony website: "A file with the ARW file extension stands for Sony Alpha Raw, and is, therefore, a Sony RAW Image file. A raw image format means that the file hasn't been compressed or manipulated in any way; it's in the same raw form it was when the camera first captured it". Sony Alpha Raw files are leggible wth Resolve, so can be input without transcoding. Current max reolution is 6.5k.


Netflix specifies camera models acceptable for their productions, and the other streaming services seem to follow suit. These requirements mean that the ARRI Alexa, ARRI Alexa Mini, and ARRI Amira cannot be used on original Netflix productions. If you want to use an ARRI camera then you can choose between the ALEXA 65 or the recently added ALEXA LF.

This is because Netflix specifications state that a camera must have a true 4K UHD sensor (equal to or greater than 3840 photosites wide) and that 90% of the total runtime of a final program should be captured on an approved camera. The only exception to the 90% rule is for nonfiction content, where the threshold can be more flexible.

Also any cameras other than the primary camera (crash, POV, drone, underwater, etc.) must be approved.

Anyone mastering images for later viewing on any display must use an accurately calibrated grading display. There is no alternative to this, regardless of the expected viewing environment or relative accuracy of the final displays the material will be viewed on. This includes material expected to be viewed in a theatre; on home TVs; on the web; on mobile phones & tablets, with digital signage - in other words, anywhere.


Calibration is achieved by the use of a probe, which measures the amount of light in the environment as a first operation. Steve Shaw of Light Illusion states that the ambient light for Home Entertainment should be 10 nits (just under 3 foot lamberts). The room is set at 10 nits by regulating the lights and using black cloth.  Care should be taken to avoid as far as possible reflections on the grading screens, and the room itself should be preferably without windows to exteriors with their associated changing light. One fairly inexpensive solution to expedite set up time and the amount of ambient light is to use  pop up gazebo such as the one in this link and make a "room within a room".


Once the ambient light level is ascertained and then set up in the Light Illusion software, then the probe is used to measure the screen's brightness, gamma and colorimetry with a sequence of specific colour patches displayed. Finally, the software elaborates a 3d LUT from the readings, and this is applied to the images sent to the Apple XDR screen so that it will display the colours, gamma and intensity we need for specific projects.


For theatrical deliverables, image calibration can be achieved if there is a room that can be darkened so that it can become as dark as a Cinema. The afore-mentioned pop up gazebo may work well for this too. Calibration for digital signage needs to take into account whether this is going to be displayed in interiors or exteriors and the Apple XDR screen rotates easily to become a vertical display for this and other vertical formats. Events will also have a particular calibration depending on the lighting at the event itself.


Calibration with Steve Shaw's Light Illusion

Some Digital Camera Examples

  More information on Digital Cameras from Netflix

RED'S REDCODE From the Red Digital Cinema website: "Raw is the revolutionary wavelet-based compression codec that unlocks incredible image capture potential and creative flexibility allowing creators to capture anything from 4k to 8k raw with manageable file sizes and lossless image fidelity.                                                            


BLACKMAGIC RAW From the Black Magic website: "Black Magic Raw is a modern codec, easier to use and much better quality than the most popular video formats, but with all the advantages of reduced data. It gives us visually lossless images, ideal for high resolution, high frame rate and high dynamic range workflows. Incredible image quality, extensive metadata support, and highly optimized GPU and CPU accelerated processing make Blackmagic RAW usable for capture, post-production, and finishing. In particular, the Blackmagic Raw format offers more color bits, making it excellent for color correction. This includes the new 12k camera.

ARRI now offers a more user-friendly workflow with Pro Res HQ, available on the latest cameras. The current maximum resolution is 6.5k.







These are clever compromises developed to get the best possible image quality out of digital cameras without over-doing the amount of data required. This has somewhat an effect on the complexity and cost of post production. and is worth taking into account when choosing digital cameras for a project.

More than 20 years ago Peter Swinson of Rank Cintel demonstrated the benefits of using higher scanned resolutions to obtain higher image quality using relatively small amounts of data. I was privileged to have seen the demo myself. Thanks to him, and when major camera manufacturers developed the concept, we understood that the higher the resolution, the more effective and visually lossless image compression becomes, and the better the end result will be.

Red Digital Cinema has developed over the last 20 years a wide range of digital cameras with very high resolution sensors offering the best possible image quality, and the manufacturer has built on raw files to make post production as efficient as possible.

In terms of data rate the Red in 8k Raw at 24 fps., and not too much compression, generates roughly 500 Mbits/sec. This is an amount of data eminently manageable in post production. On the other hand uncompressed formats such as Arriraw can require 5800 Mbits/sec. and more data rate. This puts some stress on post production hardware, which, in the end translates into greater expense. However, Apple's new Pro Res HQ can solve this issue with a data rate of around 500 Mbits/sec. This is now becoming available on the latest generation of Arri cameras, so that the cameras create the format in camera, and we don't have to waste time transcoding from Arriraw to Pro Res HQ.

Black Magic Design has also created their own sauce of raw for their digital cameras, and now many other manufacturers are following suit and are offering improved post production solutions.