When thinking to produce a video using HDR a lot of doubts come to our mind. Let’s try to clarify them with the possibilities we have when producing an HDR video.
Author: Yeray Alfageme,
Business Technology Manager Olympic Channel
What is HDR?
Let’s remember what is HDR. The acronym means High Dynamic Range and it refers to the luminosity of the image. An SDR image, Standard Dynamic Range, is the image we have been acquiring and representing in our TVs since the beginning of the colour TVs so far. When talking about live transmission HDR obliges to go from 8-bit signals to 10-bit in order to represent the luminosity. Something similar happens when file-based workflows, different formats and tools are needed.
Consider that here we are not talking about the definition, this is another discussion, but a lot of professionals and consumers prefer HD-HDR images than 4k-SDR ones and that’s why to understand what the implications are on working on HDR is so important.
Also, let’s not mix HDR with WCG, Wide Colour Gamut. We can shoot and produce HDR content based in the old BT.709 colour space without going to BT.2020.
Image acquisition – the camera and the standard
The camera selection is not an issue at all. Most of the actual cameras can capture more luminosity than the one we can record and store. Also, most of our smartphones have HDR capabilities but there is something we need to take care of when selecting our camera and it is the standard, we want to shoot in. We are not going to focus this article on what camera to choose, there are too many options and it depends on many considerations.
As we already mention in our trilogy about UHD there are, mainly 3 standards when talking about gamma curves for HDR:
- PQ – Dolby Vision: proprietary standard used in almost all the Hollywood cinema companies with great image quality but forced to be consistent from capturing until the final viewer.
- HLG – Hybrid Log Gamma: arises from the collaboration between BBC and NHK it seems to be the standard when talking about live transmissions and the most frequently used in TV. Retro compatible with SDR.
- Sony S-Log 3: proprietary standard from Sony when using Sony cameras and systems both for live and recorded shooting. It can be converted to any of the other formats using an image/signal converter from Sony.
Here we need to consider that none of our commercial TVs we have at home can reproduce any of these standards, so the final grading of our image needs to be adapted to this. The standard used at home could be either Dolby Vision, but not a complete version of it, or HDR 10.ant better pixels and that is why HDR matters.
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