All major manufacturers seem to have their own raw file format. How many of them are? Do they all have similar information? Is there any standard?
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There are a lot of different RAW file formats, not compatible with each other. The Wikipedia page has a list of them. Some manufacturers have used more than one format. There are some things they tend to have in common. Most of them are based on the TIFF file format. The TIFF file format can contain various types of image data and metadata, and it has been adapted by camera manufacturers to carry the raw sensor data from the camera sensor. Almost all modern sensors use the same RGGB Bayer interpolation matrix. While some may read in 12-bit and some in higher bit depths, the layout is the same. This is often also compressed using a common type of lossless data compression. RAW files almost always contain a low-bitrate, large JPEG image stream allowing for fast previewing on the camera LCD, but with the ability to zoom in on detail too. This is in addition to a small thumbnail in many cases. RAW files need to preserve the same metadata streams as the camera would need to create the equivalent JPEG - this means EXIF/XMP data. The proliferation of mutually incompatible formats has led for the push to standardise, and the DNG format owned by Adobe is one attempt at creating a (comparatively) open, manufacturer-agnostic format that can be shared. However, the effectiveness of such a format is only as good as the manufacturers' support for it. Some cameras do support the DNG format directly, but they are as yet in the minority. In the meantime, open source code for reading virtually any RAW format is readily available, even though RAW files tend to include some encrypted data. Lots more information about RAW formats is available on the Wikipedia page so I'd recommend it. |
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