What is the relationship between RAW, RGB and JPG?

Camera RAW, RGB and JPG each play an important role in digital image processing, what are the differences and connections between them? Danny Wony, senior engineer at Xuan Zhan Technology, elaborates:  

RAW, RGB, and JPG

 

RAW format

1. RAW Definition:

RAW, translated into Chinese means "unprocessed" meaning, for example, Raw Data refers to raw data. In digital image processing, RAW format is an unprocessed raw image data format that preserves the most realistic light signal captured by the image sensor. RAW data comes directly from the camera's photosensitive chip (such as CCD or CMOS) and is the initial image data after photoelectric conversion. 2. the bit depth of RAW format The bit depth of the RAW format refers to the way the camera sensor records image data, which represents the amount of color information contained in each pixel, usually expressed in binary bits. The bit depth of the RAW format is usually between 8 and 16 bits, or even higher. The greater the bit depth, the more color information each pixel can represent, and the richer the color level and detail performance of the image, here, the bit depth can also be understood as the resolution of light intensity information. For example, the 14-bit RAW format can record 2 to the 14th power, or 16,384 levels of depth, compared to the 8-bit JPG format can only store 2 to the 8th power, or 256 levels of light depth, RAW format can record much more information.   Therefore, the high depth of the RAW format is one of the important reasons why it can retain more image detail and color information, and it is also one of the main reasons why photographers and post-production personnel favor the RAW format. They can fine-tune and optimize images as needed in post-processing without loss of image quality.   3. What data are there in RAW images RAW images contain a large amount of raw image data and metadata, including: camera model, pixel data, pixel arrangement order, ISO Settings, shutter speed, aperture value, white balance, saturation, contrast, and more.   This data provides users with a great deal of post-processing space, allowing them to maximize their artistic talents. At the same time, since the RAW format is uncompressed, the image quality is preserved to the greatest extent. 4. Advantages of RAW format RAW format images have the advantages of lossless picture quality, large post-processing space, flexible color management, and strong compatibility, which make RAW format the preferred format for professional photographers and photography enthusiasts, because it allows them to further optimize the image after shooting and obtain higher quality works. However, it is important to note that files in RAW format are generally larger than compressed formats such as JPEG and require more storage space and processing time. Therefore, when using the RAW format, you need to weigh its advantages against the cost of storage and processing. SONY ILX-LR1 Full-frame expandable system remote control camera, support to set RAW format, coupled with 61 megapixel full-frame image sensor, take a picture after amplification can obtain details, previously may need to take more than 3 photos. The SONY ILX-LR1 demonstrates excellent performance and utility in detail capture, post-processing, and application scenarios. Not only can it help drones improve efficiency in a number of areas, but it also becomes a useful tool in the hands of photography enthusiasts and professional photographers.

RAW to JPEG principle

Let's move on, how is the RAW format converted to our common JPEG format? This relates to the white balance.

1. Establishment process of RAW to RGB mapping relationship Linearization: First, the pixel values of the RAW format image are linearized, usually the maximum and minimum pixel values of the image are linearized to the range 0-2^16-1. This step is to facilitate subsequent processing and reduce the complexity of data processing. White balance adjustment: White balance is an algorithm used to correct color distortion in an image. In the RAW to RGB conversion process, adjustments need to be made according to the white (or near-white) pixels in the image to restore the true color. Different white balance algorithms may produce different RGB images, so it is necessary to choose the appropriate algorithm according to the actual situation. De-mosaics (de-Bayer array) : The RAW data format generally uses a Bayer arrangement, which produces a color filter array (CFA) through a filtered optical plate. In the Bayer arrangement, there are twice as many green pixels as red and blue pixels because the human eye is sensitive to colors in the green band. The process of de-mosaicking is to derive the color information of each pixel from the RAW data arranged by Bayer. Color space correction: Color space correction is used to calibrate colors to correct any biases that may exist due to color distortion or camera color inaccuracies. This step ensures that the converted RGB image has an accurate color representation. Denoising: Removing noise from images is an important step to improve image quality. In the process of RAW to RGB conversion, some denoising algorithms are usually used to reduce the noise in the image. After a series of operations, the RGB data is obtained. At this time, a lot of information is actually lost, and the loss of this information also reduces the modifiable space of these files. 2. RGB format to JPEG format The conversion from RGB format to JPEG format is primarily an image lossy compression process that does not involve white balance adjustment. At the same time, JPEG, as a lossy compression format, will irreversibly reduce the image quality in the process of compression. Comparison table between RAW and JPEG   Sum up RAW format images retain the original data of each pixel captured from the sensor, so when shooting RAW format images, the white balance setting does not directly affect the image data, which can be converted to RGB color mode in post-processing. In the post-processing, the photographer can adjust the white balance according to the need, the adjustment of the white balance will affect the value of each color channel in the RGB color mode, so as to change the overall tone and atmosphere of the image, to correct the color temperature deviation of the image, and get a more accurate and natural color performance.