What is an image in RAW format?

RAW file is a file that records the original information of digital camera sensor and some original data (such as IS0 setting, shutter speed, aperture value, white balance, etc.). ) camera shooting production. RAW is an unprocessed and compressed format, which can be conceptualized as "original image encoded data" or more vividly called "digital negative".

The biggest advantage of RAW is that it saves the most original CCD data and puts more freedom in the hands of users. Recorded the most original and true information, without modification and alteration, leaving a broad operability for post-production.

How to get RAW format files?

You must have a camera that supports RAW format to create RAW format files. Most SLR cameras support shooting in RAW format, but you need to save the camera in RAW format before shooting. Different brands of cameras have different file suffixes in RAW format, and most camera manufacturers have software that can handle their own RAW files. With the attention of digital photographers and post-designers, a variety of professional RAW processing software has appeared in the market, which can support the RAW format files output by various brands and models of cameras, and also has more professional functions. In the next article, several senior moderators of post-professional video website (www.swcool.com): Underground, Xiaoding, Orange, Six Dynasties and Chen Chen, will introduce six mainstream RAW processing software in detail.

What items can RAW adjust?

1, white balance: including color temperature and hue. "Color temperature" is a white balance setting, which can be adjusted in the camera when shooting (effective for JPEG and RAW at the same time). However, when shooting JPEG, once the white balance is set, it cannot be changed afterwards. Don't think that it can be set accurately without a color temperature table. The screen behind the camera cannot accurately judge whether the color temperature setting is accurate. If you want to change it afterwards, you can only change the color in PS (you know, changing the brightness, color and other adjustments in PS will cause some loss of image details. The greater the change, the more times it is changed, and the more image details are lost! ); However, using the RAW format, adjusting the color temperature during conversion is equivalent to resetting the white balance during shooting (just like the continuation of the shooting process), and the adjustable range is very large, which is the "re-creation" of photography. The adjustment range of "hue" is much larger than that in the camera!

2. Change of exposure: It can be changed by plus or minus 4 times, which is the re-creation of photography. With layer mask in PS, we can find rich layers in almost all areas of the picture on the same picture. I have demonstrated to many people (including at school) how Zhang Daguang can control the layers in the brightest and darkest areas at the same time, but if JPEG format is overexposed and has "dead white" areas, it will be completely blank. This method is often used in many aspects, such as backlight photography under strong light, photography under stage spotlight and so on.

3. The contrast and saturation can be adjusted by adjusting the dark part and the bright part respectively;

4, sharpness adjustment: its adjustment is much more natural than the sharpening in PS, and the adjustment is moderate, leaving no traces afterwards, but the clarity has improved a lot!

The images taken by digital cameras are all "soft" and not clear enough. When shooting JPEG format, cameras usually sharpen quietly, and the effect is natural (the sharpening range of professional cameras is relatively small, such as Canon's 1 series, Nikon's D2X, etc. ). If you don't think it's enough, you can add some more to the camera (professional cameras have a wide adjustment range, such as Canon's 1D, which can not only adjust the sharpening degree, but also adjust the sharpening influence area), but it is far worse than shooting with RAW and then changing it in the conversion window. (The sharpening adjustment of the camera does not apply to files in RAW format. )

5, the processing of noise and color, the processing of purple edge-this is not available in Canon's DPP software. Some people say that the pictures taken by RAW are more cluttered than JPEG, because the camera has done some processing on JPEG. RAW is not an image format, but a collection of original image information. After PS conversion window processing, the effect is much better than JPEG shooting relying on camera processing!

6. Treatment of dark corners: Wide-angle lenses sometimes lose light in four corners. For example, Canon's 17-85mm lens is made for small digital chips, and can only be used on 1.6x Canon cameras (currently, it can only be used on 300D, 350D and 20D cameras), with dark corners at the wide-angle end. By processing the original converter,

How to choose RAW format, TIFF format and JPEG format?

The advantage of JPEG format is that the file capacity is relatively small and more photos can be stored. The storage speed of JPEG format is quite fast, especially compared with RAW format. It can capture instant shots. In terms of compatibility, it is also the best among several formats. More than 95% graphics processing software can directly open JPEG format pictures.

The disadvantage of JPEG format is obvious, because the photos taken have been adjusted inside the camera, such as color temperature, color balance, image clarity and other information has been fixed, and the later adjustment can only be made through professional graphics software, but the quality of the image will be lost.

TIFF format is a lossless compression format (the highest compression ratio is 2-3 times). This kind of compression is the compression of the file itself, that is, it records some repeated information in the file in a special way, and can completely restore the file, maintaining the original color and hierarchy. Advantages are better image quality and compatibility than RAW format, but it will take up a lot of space.

RAW format is a proprietary format of every camera manufacturer, and these files are lossless compressed. When the digital camera is exposed, the CCD (or CMOS) photosensitive element will record the light quantity of each pixel with a level meter, and then the digital camera will convert these electrical signals into corresponding digital signals, which are generally recorded as 12 bits or 14 bits of data. If the digital camera records the data of 12 or 14, it means that each pixel has 4096 or 16384 different brightness levels. If RAW is selected as the file storage format, it can be saved as 16-bit TIFF or PSD format for output by RAW conversion tools, while digital cameras record 12 or 65438. However, if you choose JPEG format to store the file, the software in the camera will convert it into 8-bit mode, which means that only 256 brightness levels can be recorded. Of course, the biggest advantage of RAW format in practical use is that it can make exposure compensation and color balance for the original recorded data on CCD (or CMOS) photosensitive elements during conversion, and the image quality will never be damaged.

RAW has obvious advantages, but its disadvantages are also obvious. Firstly, the pictures in RAW format need relevant supporting software to export photos. Secondly, the storage speed is slow and the file capacity is relatively large, but it is faster than that in TIFF format, because the original unit data of RAW only needs 12 or 14 bits of data storage, while TIFF format needs 16 bits of data storage, which makes the size of RAW format much smaller than TIFF format.

As can be seen from the above, although the RAW format has many advantages in the later period, it also has the disadvantages of large file size and slow speed. So don't treat the RAW format as a dead dogma, but choose it flexibly according to your actual situation. If post-adjustment is required and the quality of the work is very high, we should choose the RAW format to shoot, then make the necessary post-adjustment through RAW software, save it as TIFF format (Camera Raw can be edited directly in Photoshop after adjustment), then use Adobe Photoshop and other software for post-design and creation as needed, and finally output it as PSD format, TIFF format or JPEG format according to the actual standard, which can minimize the quality loss of the picture and control the quality more strictly.