HDR (High Dynamic Range) technology is a recently popularized imaging technique used to capture more natural and realistic images. It has found widespread applications, especially in Audio/Visual devices and digital cameras. Here, we'll delve into what HDR technology entails, the differences between HDR and SDR, the relationship between HDR and 4K, and where HDR is commonly integrated.

What is HDR?

To begin, HDR stands for High Dynamic Range. Simply put, HDR can be described as a feature that enables capturing images that appear natural and true even in bright or dark settings.

It's a highly prevalent technology in the new generation of imaging, extensively used in content such as UHD Blu-ray discs, Netflix, Amazon Prime, among others. Notably, most smartphone cameras introduced in recent years come equipped with HDR technology.

The support for HDR in devices has become a crucial factor in selecting Audio/Visual equipment, drawing significant attention as a defining technology.

The difference between HDR and SDR

HDR is a technology opposite to the traditional SDR-Standard Dynamic Range (standard dynamic range). The specific difference is that Audio/Visual equipment equipped with HDR is better than SDR equipment in terms of "brightness display performance" of images.

First of all, dynamic range refers to the "range of light that can be exposed" in a device (sensor) that captures images, such as a camera. The amount of ambient light is very important when recording images, but the impact of the amount of light is more pronounced when this dynamic range is narrow. Among them, Bai Fei and Hei Yong are its representative influences.

White blur is a phenomenon that occurs when the amount of light at the location exceeds the dynamic range in the environment where the image was shot. Typically camera sensors can only consider amounts of light above their dynamic range as "white". Then, since the brightness is treated as white, the captured image will have an overall white cast. Such images often lose tonal gradation and look completely different than they actually are. This "phenomenon in which the amount of light is too bright and causes the image to lose its vivid color" is white fly.

Conversely, black surge occurs when shooting in dark environments that exceed the dynamic range. In a dark place beyond the dynamic range, the sensor will recognize the extremely small amount of light as "black", as opposed to white light. The image where black surge occurs will be overall darker, similar to white fly, losing vivid colors. Such images also suffer from color brightness.

The biggest difference between HDR equipment and SDR equipment is that they are almost not prone to white fly and black surge.

Devices equipped with HDR technology can capture the accurate amount of light in a light range (cd/m2) that is approximately 100 times that of SDR devices. This is a number that was unimaginable with previous Audio/Visual devices, so HDR technology enables the creation of more natural, colorful images in environments where it was previously difficult to create accurate images.

About the relationship between 4K and HDR

In recent years, 4K has become more and more common as a synonym for high image quality. However, there is actually no technical connection between HDR and 4K, which are related to high-definition technology. This is because in order to recognize Audio/Visual equipment as 4K equipment, the evaluation criteria do not include content related to "brightness performance", an important element in HDR technology.

Existing standards for evaluating image quality include five elements: resolution, bit depth, frame rate, color gamut and brightness. The new standard "BT.2020 (involving 4K/8K technology)" stipulates the four elements of resolution, bit depth, frame rate and color gamut. However, there are no clear standards for brightness. Although the industry has a minimum value of 100cd/m2 as a basic standard, this standard is inherited from the era when TVs were still cathode ray tubes. Regarding brightness, even in the 4K era, it is still an old standard.

Technological innovation in recent years has promoted the birth of HDR, which has greatly increased the dynamic range that can be expressed. Therefore, the brightness factor related to significantly improving image quality has become more important. In the early days of 4K technology, HDR technology was continuously applied to 4K-capable Audio/Visual devices as added value. Therefore, you can enjoy more realistic and colorful image performance on these devices than traditional 4K.

Currently, HDR is mainly focused on cameras (including on smartphones) and PC monitors. Especially for smartphones, it is foreseeable that there will be more and more devices compatible with 4K+HDR functions.