What does raw format mean?

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

The operating environment of this article: windows7 system, DELL G3 computer

What does the raw format mean?

RAW's original meaning is "unprocessed". It can be understood that a RAW image is the raw data in which a CMOS or CCD image sensor converts the captured light source signal into a digital signal. A RAW file is a file that records the original information of a digital camera sensor and also records some metadata (Metadata, such as ISO settings, shutter speed, aperture value, white balance, etc.) generated by the camera shooting. RAW is an unprocessed and uncompressed format. RAW can be conceptualized as "original image encoding data" or more vividly as "digital negative". The full name of RAW format is RAW Image Format, which is called original in programming.

File format

Advantages

·RAW files are almost never processed directly from CCD or CMOS Information, through post-processing, photographers are able to maximize their artistic talents.

·RAW files do not have white balance settings, but the real data has not been changed, which means that the author can adjust the color temperature and white balance arbitrarily without any loss of image quality.

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

·Although RAW files are accompanied by saturation, contrast and other mark information, their actual image data has not changed. Users can freely make personalized adjustments to a picture without having to base it on one or two preset modes.

·Perhaps the biggest advantage of RAW is that it can be converted into 16-bit images. That means there are 65,536 levels that can be adjusted, which is a big advantage for JPG files. This is very important when editing an image, especially if you need to make important adjustments to the shadows or highlights.

Compared with JPG format, what are its advantages?

Characteristics of JPG format: The advantages of JPG files are small size and good compatibility, because most programs can read this kind of file. This is because the JPG format is not only an industry standard format, and it is the standard file format of the Web. But on the other hand, the reason why JPG is small is that some data is lost when the file is created, that is, the file is created through a "lossy" compression method. This is why the file is small.

If a digital camera uses JPG as the photo storage format, it can save valuable space, but the downside must also be seen clearly: all the processes such as color temperature, color balance, image sharpness, etc. that can be adjusted in the camera The camera's processing is recorded in the file, and post-processing adjustments can only be made through Photoshop processing, but the adjusted image quality will be lost.

If you save the file in RAW format, the camera will create a header file containing information such as sharpness, contrast, saturation, color temperature, white balance, etc., but the image will not be affected by these settings. Changes, they simply mark the RAW file. The RAW file is then saved to the memory card along with these relevant settings and other technical information.

Some cameras compress these files and some don't. As long as these compressions are "lossless", they will not have any impact on image quality, but some companies (Nikon and Kodak) explicitly use a slightly lossy algorithm to save RAW files.

Select JPG format to store files, what will be the result?

·The imaging chip is a linear device. This means that when one pixel receives twice as much light as another, it will produce twice as much voltage. When the exposure is stopped, the brightness value is expressed in its logarithm, which means that an uncorrected photo will look darker and therefore needs to be adjusted correctly through the tone curve.

·If digital photos are not sharpened, they will look flat and have low contrast, so they will appear unclear. People want JPG files to look good off-camera, so the camera performs USM (Unsharp Masking) processing on JPG files. USM will find the edges between light and dark areas and increase the contrast. Doing so will produce halos near these edges. If the sharpening setting is too high, these halos will become very obvious in the output, but If they are too low, the sharpening effect will not be achieved.

·Contrast can be set on the camera.

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

·The camera converts the file from 12-bit or 14-bit mode to 8-bit mode. In other words, the 4096 to 16384 brightness levels per pixel are suddenly reduced to 256.

·JPG is defined as a lossy compression format. Although the file is very small, it also affects the image quality.

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

Calculation method

Each pixel of traditional CCD can only sense one color, and it is converted into different numbers according to the intensity of light sensitivity. This number range is different for different CCDs. It's different, from early 8bit to 10bit and 12bit. 8bit is a point of light sensitivity divided into 256 levels from darkest to brightest, 10bit is 1024 levels, and so on.

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

3,000,000 * 10bit = 30,000,000 bit = 3,750,000byte ≈ 3662.1K ≈ 3.58M

Generally, cameras will also compress raw files, which is a lossless compression algorithm similar to zip, and the files will be smaller.

For more related knowledge, please visit the FAQ column!

The above is the detailed content of What does raw format mean?. For more information, please follow other related articles on the PHP Chinese website!