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January 30, 2024

RED Brings Global Shutter to V-Raptor (X) and V-Raptor (X) XL 8K Cameras

RED Digital Cinema has been a long term supporter of 8K content capture (see this report of a webinar by CTO, Uday Mathur). Now the company has added a global shutter sensor in its  V-RAPTOR 8K VV and V-RAPTOR XL 8K VV cameras. The global shutter feature was previously implemented in its 6K (19.9 MP) Komodo cameras.

The announcement provided a good opportunity for us to look at the pros and cons of global shutter technology.

What is Global Shutter Operation?

One of the challenges of making higher resolution sensors for digital cameras is that the sensors produce a lot of data. RED’s  8K (8192 x 4320 35MP) sensor also uses 16 bits (2 bytes) of data so at the full frame rate of 120Hz, there is a total of 8.49 GB/second coming off the sensor. This is compressed before it gets onto the memory card, but it’s an awful lot of data. One way that camera companies cope with this high level of data is to capture it and transmit it on a line by line basis. The downside of this approach is that there is a time lag between the first line being captured at the top of the frame and the last line at the bottom.

The effect of this time lag is to cause an effect known as ‘rolling shutter’. In extreme cases, the effect can mean that straight objects that are moving quickly may appear bent as they move during the capture perod. Sony published a nice short clip on YouTube showing the effect on a helicopter rotor.

A global shutter. captures all the lines of the image at the same time, so there is no bending or strange time-based artefacts. The full frame data is then sent to the processing for storage.

Why Are Global Shutters a ‘Thing’ at the Moment?

Sony announced the first full frame mirrorless camera to feature a global shutter, the A9 III, at the end of 2023. That caused a lot of excitement about the potential for better sports photography, among other things. However, the A9 III has only a 6000 x 4000 ‘6K’ shutter, so it can’t capture 8K.

As well as avoiding the rolling shutter problem, the A9 has a very fast exposure mode that allows exposure times down to 1/80,000 of a second. This allows a different approach to flash photography.

The high shutter speed can also allow special arrangements to minimise artifacts when large LED displays are in the picture. LED displays used different rates of digital update to create gray scale in their images. That can cause cameras to only capture some of the data in the image leading to strange effects.

All these features have led to a lot of buzz around the A9 III even though it is limited to 6K.

The RED V-Raptor (X) and V-Raptor (XL)

The V-Raptor (X) and V-Raptor (XL) from RED also have a special feature for virtual productions using LED backgrounds. The camera has the ability to capture two different video versions of a scene with different backgrounds when used with an LED background. This is similar to the feature offered by companies such as GhostFrame and is called ‘Phantom Track’ by RED.

The Downside of Global Shutter (or is it?)

The main disadvantage of global shutters seems to be that implementing the technology can mean a loss of dynamic range in the camera. That certainly seems to be the case with the Sony A9 III according to early reviews.

Intriguingly, RED claims that the new V-Raptor (X) cameras have a dynamic range of 17+ stops, with more available using an ‘extended highlights’ mode that is claimed to allow up to 20 stops of dynamic range. This seems to use dual exposures, with one set to capture highlights and reviewers have been impressed with the dynamic range. RED themselves said:

“Creating a global shutter sensor while maintaining dynamic range is almost impossible and then on top of that is the addition of an optional Extended Highlights mode. It shows we are pushing image processing far past the limits that were once believed and exceeding 20 stops of dynamic range. V-Raptor [X] and V-Raptor XL [X] are the result of years of incredibly difficult work internally by our world leading engineers and from the ongoing collaborative work with preeminent partners who bring invaluable experience and perspective to the process from cinema technology to virtual production, volumetric capture and live sports.”

Source:RED

The V-Raptor (X) starts at $29,995, while the XL model starts at $44,995, so they are aimed at professional content creators. 

‘DCI 8K’ Resolution

The two new cameras capture at 8192 x 4320 which is often referred to as ‘DCI 8K’. DCI is the Digital Cinema Initiative and the DCI group has been the driver of the standards used in digital cinema. However, at the time of writing, the DCI specification is limited to 2048 x 1080 (2K) and 4096 x 2160 (4K). These have a wider aspect ratio (17 x 9) than the 1920 x 1080 and 3840 x 2160 (16:9) broadcast resolutions which, along with 7680 x 2160 8K resolution, have been adopted by the ITU for UltraHD TV.

The ‘DCI 8K’ resolution, although not part of the standard, is likely to be particularly useful where content is intended for distribution at DCI 4K as it will allow downsampling to the correct aspect ratio for dealing with aliasing and other image quality issues and improvements.

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