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HDR is a video technology that has become popular in recent years, and it is said that images expressed using HDR technology are more natural and realistic. Here, we will explain what HDR technology actually is, how it relates to 4k, and what kind of equipment it is used in.
First of all, HDR stands for High Dynamic Range, and in a nutshell, HDR can be described as "the ability to capture more natural and realistic images even in areas that are too bright or too dark.
HDR is one of the most popular next-generation video technologies, and HDR technology is being used in the content of next-generation Blu-ray discs (UHD Blu-ray) and video distribution services such as Netflix and Amazon Prime. In recent years, HDR technology has been used in a number of products. And even closer to home, most smartphone cameras released in recent years are equipped with HDR technology.
Whether or not a camera is compatible with HDR technology is becoming one of the criteria for selecting an AV model, and it is a technology that is attracting a great deal of attention.
HDR is a contrasting technology to SDR (Standard Dynamic Range), which has existed for a long time. To explain the difference specifically, HDR-equipped AV equipment is superior to SDR equipment mainly in terms of " luminance representation " in video images.
Dynamic range is a term that refers to the "range of light that can be exposed" by a device (sensor) that captures images, such as a camera. When recording images with a camera, the amount of ambient light is extremely important, and if the dynamic range is narrow, the negative effects of the amount of light are more likely to appear. Typical examples of such adverse effects are " white skips " and " blackouts.
White skipping is a phenomenon that often occurs when the light level in the environment where the image was taken is brighter than the dynamic range. Generally, a camera's sensor can only capture light that is too bright beyond its dynamic range as "white. As a result, the captured image is output with an overall whitish tint. Such images often lose the color hierarchy and look completely different from reality. Such "a phenomenon in which vividness is lost from an image due to too much brightness" is called "white skipping.
On the other hand, the phenomenon that occurs when an image is shot in a dark environment beyond the range of the dynamic range is called blackout. In dark areas beyond the range of the dynamic range, a small amount of light is recognized as "black," the opposite of "white out. Images with blackout are generally darker and, as with white skipping, less vivid. The most significant difference between HDR and SDR equipment is that HDR equipment is less prone to such phenomena as white skipping and blacking out.
It is said that equipment equipped with HDR technology can accurately capture light intensity over a light range (cd/m2) that is approximately 100 times greater than that of ordinary SDR equipment. This is a figure that was unthinkable for AV equipment before the development of HDR technology, and it has made it possible to create more natural and colorful images in environments where it was previously difficult to create accurate images.
Although "4k" has become synonymous with high picture quality in recent years, there is no technical relationship between 4k and HDR, which is also related to high picture quality technology. This is because the evaluation criteria for AV equipment to be recognized as 4k-equipped devices do not include anything related to "luminance display expression," an important element in HDR technology.
There are five existing standards for evaluating image quality: resolution, bit depth, frame rate, color gamut, and luminance. Of these, standards have been established for resolution, bit depth, frame rate, and color gamut in the new broadcasting standard "BT.2020 (4k/8k technology)," but there are no clear standards for luminance. Although a minimum value of 100cd/m2 has been established as an industry standard, this is a standard that has been in place since the days of cathode-ray tube TVs, and it would be no exaggeration to say that matters related to luminance have remained unchanged even in the 4k era.
However, recent technological innovations have given birth to HDR, and the dynamic range that can be expressed has dramatically improved, making the element of luminance in image quality even more important. Some AV equipment is now incorporating HDR technology as an additional value-added feature to the existing 4k functionality, and such equipment offers more realistic and vividly colored images than conventional 4k equipment.
As of August 2021, 4k+HDR function-compatible devices, which are expected to increase in number in the future, are spreading mainly among cameras (including those mounted on smartphones) and PC monitors. In particular, most cameras for smartphones released in recent years are equipped with 4k+HDR technology, allowing users to enjoy capturing images in high quality with ease.
As for PC monitors that support 4k+HDR, most of them are currently sold in the category of gaming monitors. Most HDR-compatible PC monitors are made by overseas manufacturers, but there are a few domestic brands such as "EIZO" and "JAPANNEXT.
In terms of TVs, which are the flower of AV equipment, both domestic and foreign manufacturers have come out with models that support 4k+HDR functionality. In order to enjoy the latest hardware at 100%, it is becoming necessary to have a TV (monitor) equipped with HDR functionality.
Although HDR is extremely superior to 4k in terms of the ability to enjoy high-definition content, there are a few points to keep in mind when purchasing and using HDR-compatible equipment.
The first point to be aware of is the need to switch HDR use on and off depending on the situation, especially when using monitor-related HDR-compatible devices. At this point in time, HDR is a developing technology. Overall, there is not much content that supports HDR, and displaying content that does not support HDR with HDR turned on will often result in abnormal color reproduction. Therefore, in order to maintain the best possible picture quality at all times, the HDR function must be switched on and off frequently. If you are not concerned about abnormal coloration, it is fine to leave the switch on and off, but this defeats the purpose of using HDR-compatible equipment.
Another major point to note is that when playing back images saved on HDR-compatible equipment on non-HDR-compatible equipment, color irregularities often occur. This is not a problem if you are enjoying the saved video only by yourself (only with HDR-compatible devices), but if you are planning to upload the video to a social networking service or video distribution service, you will end up having to create the video without using the HDR function.
If you are considering using an HDR-compatible model, you will need to be convinced of these disadvantages in advance.
HDR is not always included in so-called 4k-compatible AV equipment. Depending on the intended use of the equipment, it may be considered over-specification, and if it is considered an essential feature, it is necessary to consider it at this time. However, the number of HDR-compatible devices and content is steadily increasing. If you are considering the purchase of new AV equipment and are interested in the next generation of video content, it will not hurt to check the availability of HDR functionality in advance.
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