Introduction
In this documentation, we will talk about working with HDR (High Dynamic Range) inputs and outputs using Aximmetry.
What is HDR?
Dynamic Range
Before we talk about HDR we must talk about what is Dynamic Range.
The range between the brightest and darkest values that we can capture or display is called Dynamic Range. Dynamic Range is measured in stops.
Our eyes have about 20-21 stops of Dynamic Range.
When capturing images with a camera this range is reduced, very high-end cameras have around 14 stops of dynamic range.
Most displays are working in SDR (Standard Dynamic Range) which has about 6 stops.
The higher the Dynamic Range the more details you can preserve in your images.
The following images show the difference in Dynamic Range in photos:
You can see that the upper (HDR) image preserved more details at different exposure values than the lower (SDR) image.:
Displaying SDR / HDR Content
Monitors and TVs can not show as high brightness as the real-life object would show.
SDR content is typically displayed at 200 nits. Nits are units of the brightness of monitors and TVs.
However, there are some monitors and TVs that are capable of displaying HDR content.
HDR allows much higher brightness levels than SDR. This makes images keep more details in both dark and bright parts of the image.
HDR content can be displayed at the maximum of your display device's capabilities.
What peak brightness your device is capable of displaying should be listed on the manufacturer's website.
Max brightness is usually measured in either NITs or cd/m2.
NOTE: 1 NIT = 1 cd/m2
HDR Rendering in Aximmetry
Setting the Rendering Pipeline
By default, Aximmetry is rendering in the sRGB Gamma pipeline that is only suitable for SDR content creation.
For HDR results, you should switch to sRGB Linear.
NOTE: You can still create SDR content in the sRGB Linear pipeline. In this case, the maximum brightness intensity should be set to 1 which is equal to the maximum brightness of SDR content.
To do this go to File/Properties and in the pop-up window choose Rendering and set the rendering pipeline to sRGB Linear:
Aximmetry by default renders in full HDR meaning that the brightness levels are not restricted by the software during calculations.
However, HDR output also depends on your output screen, the screen must be capable of displaying HDR content.
In Aximmetry brightness values can be converted into nits using this equation: Aximmetry brightness 1=80 nits.
HDR Preview
Previews by default rendered in SDR. If you wish to have your previews rendered in HDR too you should turn on the HDR Render property in the PREVIEW MONITOR OUTPUT control panel on the CAMERAS control board:
Tone Mapping
As Aximmetry renders in full HDR you can create brightness levels that your device is not capable of displaying and those parts of the image that exceed your display's capabilities would all become completely white leading to a loss in details and overbright images.
To countermeasure this, you can use Tone Mapping in Aximmetry. Tone Mapping is an operation, during which we map a range of color values into another range. In this case from a higher dynamic range to a lower dynamic range.
NOTE: You can learn more about Tone Mapping here.
Tone mapping in itself is not mandatory to do. But if your scene's brightness is higher than the device that it is going to be displayed on, then we recommend using it to avoid loss of details.
When working with SDR output and/or display your Max Out Lum setting should be set to 1 in the Tone Mapper.
NOTE: You should leave the Max Out Lum In Nits property turned off.
When working with HDR output your Max Out Lum setting should be set to the maximum brightness of your display device.
In this case, we suggest using Nits for setting the value by turning on the Max Out Lum In Nits property.
You can check your maximum brightness in the device's manual.
HDR Rendering in Unreal Engine
Unreal Engine Setup for Virtual and Tracked Camera and LED WALL Production
By default Unreal renders in HDR and applies tone mapping resulting in SDR content. We want Unreal not to apply Tone Mapping and output HDR content.
To do so open the Project Settings and search for Frame Buffer. Find the Frame Buffer Pixel Format setting and set it to Float RGBA:
Restart and recook your scene.
In Aximmetry
NOTE: Unreal Engine does not do Tone Mapping for HDR output, if you wish to you can do it inside Aximmetry.
With Virtual Camera go to the CAMERAS control board.
With Tracked Camera go to the INPUTS control board.
With LED Walls go to the LEDWALLS control board,
and find the HDR panel:
In the Pin Values window turn it on:
You should then adjust the Tone Mapping values.
You can learn more about tone mapping here: Tone Mapping Methods.
NOTE: You should adjust these values to the device that the content is going to be displayed on.
Unreal Engine Setup for AR Production
By default Unreal renders in HDR and applies tone mapping resulting in SDR content. We want Unreal not to apply Tone Mapping and output HDR content.
To do so open the Project Settings and search for Frame Buffer. Find the Frame Buffer Pixel Format setting and set it to Float RGBA:
In Aximmetry
NOTE: Unreal Engine does not do Tone Mapping for HDR output, if you wish to you can do it inside Aximmetry.
Go to the INPUTS control board and find the TONE MAP module:
You should then adjust the Tone Mapping values.
You can learn more about tone mapping here: Tone Mapping Methods.
NOTE: You should adjust these values to the device that the content is going to be displayed on.
Inputs and Outputs
Inputs
There are no special settings that you need to change regarding inputs, Aximmetry will detect the type of the input signal.
Outputs
When it comes to outputs there are a few settings that you should change depending on your method of outputting
- SDI
-
When working with SDI output you should set the output to 10-bit
- You can also set the Color space here
NOTE: You should set it to one of the supported HDR Color Spaces as detailed here.
-
- HDMI / DP
- When using HDMI / DP cable Windows will automatically convert the video signal to Rec.2100 PQ codec.
- Make sure that your Windows display settings are correct and that you have HDR turned on
Supported HDR Color Spaces
Here you can find all supported HDR codecs:
- Rec.2100 Perceptual Quantizer (PQ)
- Brightness is stored in nit
- HDR10 uses this codec therefore it is supported by most TVs, Monitors, and the Windows OS.
- Rec.2100 Hybrid Log-Gamma (HLG)
- 1 unit is typically the top of SDR capabilities which is 200 nit
- Sony S-Gamut3/S-Log3
- Sony S-Gamut3.Cine/S-Log3
- Panasonic V-Gamut/V-Log
- REDWideGamutRGB/Log3G10
