Sony FCB camera block
The FCB-ER9500 is SONY’s first camera module that supports 4K60 frames per second capture. With its high resolution, high frame rate, high magnification zoom and outstanding overall performance, it has attracted widespread attention in multiple industries, especially in the broadcasting and television industry, where users are particularly concerned about whether it supports the BT.709 and BT.2020 color gamuts.
In response to this issue, Danny Wong, a senior engineer from Xuanzhan Technology, the official authorized distributor of SONY (China), provided professional and detailed answers from their respective definitions, color coverage range and application scenarios.
I. Core Concept: What is color gamut?
Color Gamut refers to the range of colors that a color standard (such as BT.709, DCI-P3, BT.2020) can represent. It can be imagined as a color palette, with different color gamut standards representing palettes of different sizes.
Small color palette: Fewer colors, not bright enough.
Large color palette: More colors, more saturated, and more vivid.
Ii. Direct Comparison: BT.709 vs. BT.2020
1. Color gamut range: BT.2020 has a wider coverage and richer color representation
1) BT.709
It covers approximately 35.9% of the CIE 1931 visible spectrum, with a relatively narrow color gamut.
The red and green areas are weakly represented, and the cyan and dark blue areas are insufficiently covered, resulting in fewer color gradations in the picture and easy loss of details in the highlights and dark areas.
Applicable to traditional high-definition television (HDTV) and standard dynamic range (SDR) content, such as 1080p TV programs.
2) BT.2020:
It covers approximately 75.8% of the CIE 1931 visible spectrum and has a color gamut more than twice that of BT.709.
Red is more vivid, green is softer, and blue is deeper, which can reproduce more colors of the real world (such as deep green forests and bright red flowers).
Designed specifically for ultra-high-definition TVS (UHDTV, 4K/8K) and high dynamic range (HDR), it supports higher color accuracy and brightness range.
2. Dynamic range: BT.2020 supports HDR, with a qualitative leap in brightness and contrast
1) BT.709
It only supports standard dynamic range (SDR), with a peak brightness typically of 100 nits and limited contrast.
The bright areas are prone to overexposure (such as loss of cloud details), while the dark areas are likely to develop noise or a dull black color.
2) BT.2020:
Supports high dynamic range (HDR), with peak brightness up to 10,000 nits and theoretical contrast ratio of 1,000,000:1.
Optimize the luminance mapping through PQ (Perceptual Quantization) or HLG (Mixed log-Gamma) curves to retain more highlights and dark details (such as starry sky details and flame gradation). Combined with HDR technology, the picture is closer to the real perception of the human eye.
3. Resolution and bit depth: BT.2020 is compatible with ultra-high definition, providing smoother color transitions
1) BT.709
It mainly targets 720p/1080p resolution and 8-bit or 10-bit quantization.
Under bit color depth, the color gradient may exhibit Banding phenomena (such as the gradient layering of the sky).
2) BT.2020:
Compatible with 4K (3840×2160) and 8K (7680×4320) resolutions, it meets future display requirements.
Supports 10-bit or 12-bit color depth, capable of distinguishing 1.07 billion or 68.7 billion colors, reducing color band phenomena (such as more natural sunset gradients).
Iii. What is one color depth bit
“1-bit color depth” = 2¹ = 2 gray levels (pure black, pure white).
For every 1 bit added, the number of colors and gray levels that can be represented is multiplied by 2.
So:
8 bits = 2⁸ = 256 levels (single channel), the total of RGB three channels is 256³ ≈ 16.7 million colors
10 bits = 2¹⁰ = 1,024 levels, and the total of the three RGB channels is 1024³ ≈ 1.07 billion colors
12 bits = 2¹² = 4,096 levels, the total of the RGB three channels is 4096³ ≈ 687 billion colors
One sentence
One bit is the smallest scale that can divide brightness or color into 2 to the power of n parts.
Iv. Application Scenarios: BT.709 remains the mainstream, while BT.2020 represents the future direction
Although BT.2020 is the ultimate goal, currently, almost no consumer-grade display devices can fully achieve 100% BT.2020 coverage. Manufacturing hardware that can emit such pure and saturated primary color light is extremely difficult and expensive.
Therefore, the industry currently generally adopts an “intermediate station” – the DCI-P3 color gamut.
DCI-P3: The color range lies between BT.709 and BT.2020. It is approximately 25% higher than BT.709.
Nowadays, the vast majority of 4K HDR TVS, monitors and mobile phone screens that claim to have a “wide color gamut” aim to cover 90% to 99% of the DCI-P3 color gamut, rather than BT.2020.
The vast majority of 4K HDR movies and game content are actually produced in the DCI-P3 color space.
So, the current path is: BT.709 -> DCI-P3 -> BT.2020.
V. Regression Issues
Let’s return to the issue of concern in the broadcasting and television industry: Does the SONY FCB-ER9500 support the BT.709 and BT.2020 color gamuts?
The technical protocol manual of SONY FCB-ER9500 reads as follows: Color coding complies with BT.709, which in Chinese means: color coding conforms to the BT.709 standard.
That is to say, the SONY FCB-ER9500 supports the BT.709 color gamut but does not support the BT.2020 color gamut.