CamCyclopedia
Video HDR
Contents
- What is HDR?
2. Galaxy HDR
What is HDR?
Auto Exposure (AE) adjusts the exposure in a photo or video to get an adequately bright image.
However, when you shoot against backlight or from indoors, looking out a window, you will see that both bright and dark scenes coexist in this mixed light environment. The photos either look bright or dark, given the precedence of one.
High Dynamic Range (HDR) widens the range of displaying light and dark areas. It makes the images three to four times brighter and more visible, thereby achieving tones closer to human vision.
Galaxy HDR
Let’s take a look at the Galaxy HDR technology on S23.
The first one is MF-HDR (Multi-Frame HDR) processing.
It's a technique that takes a series of photos with different exposures, collects information from the illuminated and unlit parts of the bright and dim images respectively, and then combines them into a single photo.
It selectively synthesizes information on light and dark subjects to create an optimally bright image.
However, since MF-HDR captures multiple consecutive shots, there is a time lag between each of them. This means results are more prone to ghosting, where the motion vector and image appear to overlap in a moving subject. So, it is better to use MF-HDR in the photo mode where there is relatively lesser subject motion.
The video mode, on the other hand, works differently. It utilizes the image sensor’s intra-scene dual conversion gain (iDCG) technology to simultaneously record bright and dim scenes at one exposure and combine these together with the single-frame HDR (SF-HDR) technology.
The iDCG image sensor technology generates electrical signals of electrons depending on the brightness intensity of the light received by the photodiode of the image sensor. It converts the signals into voltage using the image sensor's internal circuit (ADC: Analog Digital Converter and Logic circuit).
In converting light into electrical signals, it calculates the number of electrons by placing them in a cup called floating diffusion (FD), the capacity of which determines a specific ratio and turns them into a voltage signal.
Traditional sensors have a single cup capacity, making it difficult to produce optimal photos against environments with many bright and dark tonal changes.
In a dark environment, a large cup can’t turn small bits of light information into enough voltage to make unlit areas look vivid and clear. On the other hand, in a bright environment, a small cup won't be able to take in all the overflowing light information and make overly bright areas look good.
The iDCG technology breaks down the existing cup into two cups with different capacities, selecting the smaller cup for darker environments and the larger cup for brighter environments. Then it calculates twice to combine the results in real time and deliver one image with enhanced HDR performance to the ISP.
This is advantageous for video because SF-HDR, which uses one exposure, has an added benefit in regard to subject movement over MF-HDR, which uses two exposures.
We are constantly innovating to bring the HDR performance closer to the human eye level with the technical expertise of camera image sensors and ISPs.
Look forward to the next Galaxy camera!
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