Explore the camera parameters and technical considerations that need to be considered when working with an LED volume and learn what you need to prepared for.
On-camera considerations when shooting on a volume
Check out the considerations you need to be aware of when capturing images for VP, related to the different camera parameters.
Focus
- Consider moire when selecting focus point
Focal length
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Focal length will be dictated by creative interpretation, this will vary depending on sensor size and aspect ratio
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The lens choice might be affected depending on whether lens mapping is required
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Ensure focal length and aperture are matched in real time player
Aperture
- Aperture setting is dictated by traditional exposure requirements – however foreground lighting may need to be balanced to specific output of LED Wall
Dynamic range (ISO)
- ISO requirements are dictated by traditional exposure requirements
White balance
- Under most circumstances white balance should be set to the foreground element, i.e. not the virtual environment
- There is a lot of flexibility within the LED processing to change colour temperature on the wall. The preferred method would be to make changes to colour temperature within real-time engines and to keep both the wall output and the wall colour temperature fixed
Shutter speed and frame rate
- Frame rate is constrained by the refresh rate of the screen and sync issues. Currently limited to +- 50FPS
Frame rate
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On occasion it may be necessary to phase shift the shutter timing to prevent artifacts and sync lines. This is less of an issue when the camera has a global shutter
Resolution
- To be determined by broadcast deliverables and post production resources
Format
- To be decided based on creative interpretation, but needs to be communicated to all interested parties. – Brain Bar, LED Tech, DIT, and production
Frame ratio
- As peer broadcasters requirements
File formats
- No known constraints
Colour space
- Dictated by specific volume, and camera selection – check if the studio has an established colour pipeline
Codec
- No known constraints / no additional considerations
Compression
- No known constraints / no additional considerations
LUT
- Do not apply show LUT to screen, only to camera output
Technical considerations when transitioning into a VP (Mixed Reality) environment on a LED volume
Specific to working with the LED wall, the camera crew also needs to be aware of the following technical considerations when transitioning from traditional location/studio work into a VP (Mixed Reality) environment on LED volume.
This will dictate how close they can shoot to the screen whilst maintaining photorealism.
To ensure correct colour balance.
Elect whether to make adjustments through lighting filtration, camera filters, in post-production, or by manipulating the LED output. Most LED screens currently in use were not designed for filming, and consequently the colour bias can cause significant problems.
Does the content have a LUT applied? Is the content HDR, 8Bit, 10Bit?
This will influence choice of frame rate and shutter angle, banding and synchronisation between the camera and the wall.
It is always good to know the original frame rate of the footage, to determine if creatively the footage is supposed to look slowed down or sped up.
Depending on what the source material is, and what the director’s intentions are, it may be necessary to use a tracking system on the camera. This tracking allows for parallax correction as the camera moves around the set. It enables the real-time playback engine to know exactly where the camera is within the environment and adjust the output to the LED screens accordingly.
This may be required to ensure that the screen output represents the image as seen by a specific focal length or style of lens. It can match all lens aberrations and individual lens traits to ensure the LED output is an accurate representation of what the camera and lens combination would see on a conventional set.
Is the LED wall being used simply as an alternative to green screen or rear projection, or is the intention to use the wall as a lighting source too? This will have practical considerations.
Consideration should be given to pixel mapping fixtures to screen content within the real-time engine environment, and if not, a decision should be made as to how to best approach colour balance, and matching foreground with LED output.
Generally when working in an LED volume you are aiming to achieve as close to final pixel as possible – consequently you are taking some time (and budget) from traditional post workflow and using it in what would traditionally be called pre-production. This method of working normally requires the engagement and involvement of the camera team, and in particular the DoP earlier in the production process. Allow enough time for testing and checking your source material before the shoot.
These are all issues that can occur if proper consideration is not given to frame rate, shutter angle, lens selection and distance from screen. Crew needs to be aware of these issues and the reasons they occur to ensure a seamless shoot day.
Explore more competencies:
Supplying and maintaining camera and related equipment for virtual production
Setting up camera and related equipment for virtual production
Learn about lighting competencies for virtual production here.