Tuesday, January 4, 2011
Hi-Tech Studio: File Format Decoder Ring
The alphabet soup of file extensions is confusing. In this brief article, we show you the differences and similarities of the most common formats.
RW2. Panasonic digital cameras utilize the RAW (with a “raw” filename extension) and RW2 file formats for recording the information gathered by the image sensor. These RAW file formats are supported by most conversion software.
SR2, SRF, ARW. Sony digital cameras have utilized several different RAW file formats, which are the SR2, SRF and ARW file formats. These file formats contain the information gathered by the image sensor, as well as additional information about the capture. Certain information is encrypted so the benefit of that information can be fully achieved only by Sony’s Image Data Converter software.
X3F. Sigma digital cameras utilize the X3F file format for RAW capture. This RAW file format is unique in that it contains the full-color information gathered by the Foveon image sensors in Sigma digital cameras. Rather than capturing a single color value (either red, green or blue) for each pixel, Sigma’s Foveon sensor gathers full RGB data for each pixel. This individual color component information, along with other details of the capture, is contained within the X3F file format.
DNG.The Digital Negative (DNG) file format was created by Adobe in response to the proprietary nature of RAW captures. The DNG file format is openly documented, which many photographers appreciate due to concerns of a future lack of support for proprietary RAW files. The DNG file format also provides the benefit of being able to encapsulate metadata directly within the file, rather than through the use of XMP sidecar files used by many applications to store additional metadata for a RAW capture (generally with the aim of not modifying the original RAW capture). A variety of digital cameras capture in the DNG file format, and Adobe also offers a free Adobe DNG Converter (www.adobe.com/dng) for converting RAW captures to DNG.
Various Compressed And Uncompressed Formats
GIF. The Graphics Interchange Format (GIF) was popular in the very early days of the Internet, but because a single GIF image can include a maximum of only 256 individual colors, it’s far from ideal for photographic images. It remains useful for certain applications, however, because of its ability to include multiple frames within the file and present those frames as an animation.
JPEG. The JPEG has become ubiquitous as the most common file format for sharing digital photos online; it’s also a capture option in most digital cameras. The JPEG file format is an open standard published by the Joint Photographic Experts Group. Compression is always applied to JPEG images, which means there will be some degree of degradation in image quality when a photo is saved as a JPEG. By adjusting the Quality setting for JPEG images, you can shift the balance between image quality and file size.
JPEG 2000. The JPEG 2000 file format was created by the same Joint Photographic Experts Group that published the JPEG standard we’re so familiar with. The cornerstone of JPEG 2000 is a “wavelet transform” compression method that enabled higher quality at smaller file sizes compared to JPEG. JPEG 2000 was intended to replace the older JPEG standard. Legal concerns related to intellectual property rights have created challenges that have caused the JPEG 2000 file format to be not widely supported, however.
PNG. The Portable Network Graphics (PNG) file format is similar in many ways to the JPEG file format. Generally, the PNG file format will produce an image of higher quality than JPEG, but with a larger file size as well. Another advantage of PNG over JPEG is that PNG files support transparency, which is helpful when you need an object in an image to blend into a background (such as a web page) of any color. Because early web browsers didn’t support the PNG file format, however, it hasn’t achieved the ubiquity of the JPEG file format.
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