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This article is about what the raw format means. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

Raw format is an unprocessed and uncompressed format, and RAW can be conceptualized as "original image encoded data" or, more vividly, "digital negative"; the full name of RAW format is "RAW Image Format", which is called raw in programming.

Operating environment of this article: windows7 system, DELL G3 computer

What does raw format mean?

The original meaning of RAW is "raw". RAW image is the original data that the CMOS or CCD image sensor converts the captured light source signal into digital signal. RAW file is a kind of file that records the original information of the digital camera sensor and records some metadata (Metadata, such as ISO setting, shutter speed, aperture value, white balance, etc.) generated by the camera. RAW is an unprocessed and uncompressed format that can conceptualize RAW as "original image encoded data" or, more vividly, "digital negatives". The full name of the RAW format is RAW Image Format, which is called primitive in programming.

file format

advantage

RAW files are almost unprocessed information obtained directly from CCD or CMOS. Through post-processing, photographers can maximize their artistic talents.

The RAW file does not have a white balance setting, but the real data has not been changed, which means that the author can adjust the color temperature and white balance arbitrarily, and there will be no loss of image quality.

Color linearization and filter row-column transformation are processed more quickly on computers with microprocessors, which allows for the application of more complex algorithms that are not allowed on cameras.

Although the RAW file contains saturation, contrast and other marking information, but its real image data has not changed. Users are free to make personalized adjustments to a particular image without having to base on one or two pre-set modes.

Perhaps the greatest advantage of RAW is that it can be converted into a 16-bit image. That is, there are 65536 levels that can be adjusted, which is a big advantage for JPG files. This is important when editing an image, especially if you need to make important adjustments to the shaded or highlight areas.

What is the advantage over the JPG format?

The characteristics of JPG format: the advantage of JPG file is small size and good compatibility, because most programs can read this kind of file, this is because JPG format is not only an industry standard format, but also a standard file format of Web. On the other hand, the reason why JPG is so small is that some data is lost when the file is created, that is, the file is created by "lossy" compression, which is why the file is small.

If the digital camera uses JPG as the photo storage format, although it can save valuable space, the disadvantageous side must also be seen clearly: everything that can be adjusted in the camera, such as color temperature, color balance, image sharpness and so on, can be recorded in the file after camera processing, and the later adjustment can only be carried out through Photoshop processing, but the adjusted image quality will be lost.

If you are saving the file in RAW format, the camera will create a header file that contains information such as sharpness, contrast, saturation, color temperature, white balance, etc., but the image will not be changed by these settings, they are just marked on the RAW file. The RAW file is then saved to the memory card along with these settings and other technical information.

Some cameras compress these files, while others don't. As long as these compressions are "lossless", there will be no impact on image quality, but some companies (Nikon and Kodak) have made it clear that they use a slight loss algorithm to save RAW files.

What happens if you choose the JPG format to store the file?

The imaging chip is a linear device. This means that when one pixel has twice as much light as the other, it will also generate twice the voltage. When the exposure stops, the luminance value is presented in its logarithm, which means that an uncorrected photo will look darker, so it needs to be adjusted correctly through the hue curve.

Digital photos will look flat and low contrast without sharpening, so they will not appear clear. People want the JPG file to look good without the camera, so the camera will USM (Unsharp Masking) the JPG file. USM finds the edges between the bright and dark areas and increases the contrast, which creates a halo near these edges. If the sharpness is set too high, these halos will become very obvious on the output, but if they are too low, they will not achieve the sharpening effect.

The contrast can be set on the camera.

Color saturation can also be adjusted on the camera, usually with two or three levels.

The camera converts the file from 12-bit or 14-bit mode to 8-bit mode, in other words, sharply reducing 4096 to 16384 luminance levels per pixel.

JPG is defined as a lossy compression format, although the file is very small, but also affects the image quality.

A RAW file is essentially data recorded by the imaging chip with some additional information; a JPG file already has some camera linear transformation, matrix transformation, white balance, contrast, saturation and other applications, followed by some potentially destructive compression applications.

Calculation method

Traditional CCD can only be sensitive to one color per pixel, which can be converted into different numbers according to different photosensitive intensity, and the range of different CCD numbers is different, from early 8bit to 10bit and 12bit. 8bit is a point light sensitivity with 256 levels from the darkest to the brightest, 10bit is 1024 layers, and so on.

Assuming that each pixel of 3 million pixels contains digital information for 10bit, its uncompressed RAW file size:

3000000 * 10bit = 30000000 bit = 3750000byte ≈ 3662.1K ≈ 3.58m

The general camera will also compress the raw file, which is a lossless compression algorithm similar to zip, and the file will be smaller.

Thank you for reading! This is the end of the article on "what does raw format mean?". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, you can share it for more people to see!

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