Page 150 - DCAP104_EXPOSURE_TO_COMPUTER_DISCPLINES

Unit 7: Graphics and Multimedia

cameras can save in TIFF format, using the LZW compression algorithm for lossless storage. Notes
TIFF image format is not widely supported by web browsers. TIFF remains widely accepted as a
photograph file standard in the printing business. TIFF can handle device-specific color spaces,
such as the CMYK defined by a particular set of printing press inks. OCR (Optical Character
Recognition) software packages commonly generate some (often monochromatic) form of TIFF
image for scanned text pages.
7.3.1.5 RAW

RAW refers to a family of raw image formats that are options available on some digital cameras.
These formats usually use a lossless or nearly-lossless compression, and produce file sizes much
smaller than the TIFF formats of full-size processed images from the same cameras. Although
there is a standard raw image format, (ISO 12234-2, TIFF/EP), the raw formats used by most
cameras are not standardized or documented, and differ among camera manufacturers. Many
graphic programs and image editors may not accept some or all of them, and some older ones
have been effectively orphaned already. Adobe’s Digital Negative (DNG) specification is an
attempt at standardizing a raw image format to be used by cameras, or for archival storage of
image data converted from undocumented raw image formats, and is used by several niche
and minority camera manufacturers including Pentax, Leica, and Samsung. The raw image
formats of more than 230 camera models, including those from manufacturers with the largest
market shares such as Canon, Nikon, Sony, and Olympus, can be converted to DNG. DNG
was based on ISO 12234-2, TIFF/EP, and ISO’s revision of TIFF/EP is reported to be adding
Adobe’s modifications and developments made for DNG into profile 2 of the new version
of the standard.

As far as videocameras are concerned, ARRI’s Arriflex D-20 and D-21 cameras provide raw
3K-resolution sensor data with Bayern pattern as still images (one per frame) in a proprietary
format (.ari file extension). Red Digital Cinema Camera Company, with its Mysterium sensor
family of still and video cameras, uses its proprietary raw format called REDCODE
(.R3D extension), which stores still as well as audio+video information in one lossy-
compressed file.

7.3.1.6 PNG

The PNG (Portable Network Graphics) file format was created as the free, open-source successor
to the GIF. The PNG file format supports truecolor (16 million colors) while the GIF supports
only 256 colors. The PNG file excels when the image has large, uniformly colored areas. The
lossless PNG format is best suited for editing pictures, and the lossy formats, like JPG, are
best for the final distribution of photographic images, because in this case JPG files are usually
smaller than PNG files. The Adam7-interlacing allows an early preview, even when only a small
percentage of the image data has been transmitted.

PNG provides a patent-free replacement for GIF and can also replace many common uses of TIFF.
Indexed-color, grayscale, and truecolor images are supported, plus an optional alpha channel.
PNG is designed to work well in online viewing applications like web browsers so it is fully
streamable with a progressive display option. PNG is robust, providing both full file integrity
checking and simple detection of common transmission errors. Also, PNG can store gamma
and chromaticity data for improved color matching on heterogeneous platforms.

Some programs do not handle PNG gamma correctly, which can cause the images to be saved
or displayed darker than they should be.

Animated formats derived from PNG are MNG and APNG. The latter is supported by Mozilla
Firefox and Opera and is backwards compatible with PNG.

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