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TIFF/EP, ISO 12234-2:2001

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Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

Full name TIFF/EP, Tag Image File Format/Electronic Photography (common name); ISO 12234-2:2001, Electronic still-picture imaging – Removable memory – Part 2: TIFF/EP image data format (formal name)
Description

TIFF/EP_1 is based on a subset of TIFF 6.0 (TIFF_6), together with a subset of EXIF tags and concepts. However, there are some differences and extensions. TIFF/EP_1 was intended as suitable as a raw camera image format and to be as compatible as possible with TIFF 6.0. A TIFF/EP_1 file is a valid TIFF file that contains the TIFF/EP format identifier and conforms to certain restrictions described in ISO 12234-2:2001. The TIFF/EP_1 header is exactly the same as the TIFF header. The use of the TIFF/EP format and revision number is identified in the TIFF/EPStandardID tag-field (Tag 37398); this tag is mandatory for a TIFF/EP file. ISO 12234-2 (TIFF/EP_1) introduced several new TIFF tags; which will be ignored by a baseline TIFF viewer. See Tags for TIFF and Related Specifications for more on TIFF tags.

Differences from EXIF are more substantial. In particular, values for a few metadata items are stored using different tags and a different method for including a thumbnail in a TIFF file is specified.

Although TIFF/EP_1 was not adopted by most camera manufacturers per se, it did serve as the basis for Adobe's DNG and some manufacturers' raw formats.

TIFF/EP_1 readers must handle images stored in uncompressed form, or using JPEG baseline DCT-based lossy compression as specified in Adobe Photoshop: TIFF Technical Notes (March 22, 2002). Other compression schemes are permitted but readers are not required to handle them. TIFF Tag 259, mandatory in TIFF/EP, indicates the Compression method: 1 for uncompressed; 7 for JPEG baseline DCT-based lossy compression. If an image compression method is used in TIFF/EP, an uncompressed Baseline TIFF-readable "thumbnail" image (with a reduced-resolution) should also be stored in the 0th IFD, to allow the images to be viewed and identified using a Baseline TIFF 6.0 reader.

Production phase Intended as a standard raw image format for digital cameras.
Relationship to other formats
    Subtype of TIFF_6, TIFF, Revision 6
    May contain Uncompressed image data as in TIFF_UNC.
    May contain JPEG_DCT_BL, JPEG DCT Compression Encoding, Baseline. As defined in ISO/IEC 10918-1:1994. TIFF/EP readers must be able to decode this compression encoding.
    May contain JPEG_orig_LL, JPEG Original Lossless Compression (ISO/IEC 10918). TIFF/EP readers are not required to decode images compressed with this encoding. The compilers of this resource assume that the "JPEG Lossless Compression" referred to in ISO 12234-2:2001 is the lossless encoding from ISO/IEC 10918:1994, which is a included as a normative reference. The specification for TIFF/EP makes no mention of ISO/IEC 14495:1999, which introduced another lossless JPEG encoding (JPEG_LS). Comments welcome.

Local use Explanation of format description terms

LC experience or existing holdings  
LC preference  

Sustainability factors Explanation of format description terms

Disclosure Open standard. Prepared and maintained by ISO/TC 42/WG18, Photography, Electronic still picture imaging.
    Documentation ISO 12234-2:2001, Electronic still-picture imaging – Removable memory – Part 2: TIFF/EP image data format
Adoption

Because a TIFF/EP_1 file is a valid TIFF 6.0 file, all TIFF viewers should be able to open a TIFF/EP_1 file. However, professional image processing tools are necessary to take advantage of the raw image data and all the metadata that may be in a TIFF/EP file.

TIFF/EP_1 was not adopted per se by leading camera manufacturers as a raw image format standard, the original intent for the specification. Meanwhile, as of December 2010, according to a table compiled by Barry Pearson, a number of manufacturers have adopted Adobe's DNG format (described in the DNG specification as an extension of TIFF/EP) as a native format or an optional output from the camera, while others continue using a proprietary raw format. Some manufacturers' raw formats take advantage of the tags introduced in ISO 12234-2:2001 and may, as in Nikon's raw NEF format, according to Barry Pearson's What's in a Raw File?, include a TIFF/EPStandardID tag (37398). Adobe's DNG, version 1.1 format specification states that a file can comply with the TIFF/EP_1 standard and also be a valid DNG file. The compilers of this resource are not aware of any product that produces files that comply with both specifications. Comments welcome. See Notes below for more on relationship of TIFF/EP_1 to DNG 1.1.

    Licensing and patents TBD
Transparency Depends on bitstream encoding.
Self-documentation See TIFF_6.
External dependencies None
Technical protection considerations None

Quality and functionality factors Explanation of format description terms

Still Image
Normal rendering See TIFF_6.
Clarity (high image resolution) See TIFF_6.
Color maintenance The ICC (InterColour) profile, contained in the InterColourProfile tag-field (tag 34675), may be used to provide the information required to interpret the digital code values of a color image. See also TIFF_6.
Support for vector graphics, including graphic effects and typography No support for typography or vector graphics
Support for multispectral bands TIFF/EP_1 is not intended for multispectral use. All TIFF/EP readers shall handle greyscale, RGB and YCbCr data.
Functionality beyond normal rendering Image data may optionally be stored using a single image component having a color filter array (CFA) area pattern of the image data derived from a single-chip color CCD image sensor. However, TIFF/EP readers are not required to handle this raw type of image data. The tags used to describe a CCD’s CFA pattern in TIFF/EP_1 are: SamplesPerPixel, PlanarConfiguration, CFARepeatPatternDim, CFAPattern and SensingMethod.

File type signifiers Explanation of format description terms

Tag Value Note
Filename extension tif
tiff
 
Internet Media Type See related format.  See TIFF_6.
Magic numbers See related format.  See TIFF_6.
Indicator for profile, level, version, etc. 1 0 0 0
Tag 37398 (TIFF/EPstandardID) is mandatory for TIFF/EP and indicates the version of the TIFF/EP standard in use. The value shown here is for TIFF/EP_1, as specified in ISO 12234-2:2001.

Notes Explanation of format description terms

General

TIFF/EP_1 uses the TIFF/JPEG specification as described in Adobe Photoshop: TIFF Technical Notes (March 22, 2002). This method differs from the JPEG method described in the original TIFF 6.0 specification. In the method used within TIFF/EP_1, each image segment (tile or strip) contains a complete JPEG data stream that is valid according to the ISO JPEG standard (ISO/IEC 10918-1).

In TIFF/EP_1 files, the 0th IFD should be an image that can be read by a baseline TIFF 6.0 reader. Since JPEG compression is not required for baseline TIFF 6.0 readers, if the full-resolution image is stored using compression, the TIFF/EP_1 file should include an uncompressed thumbnail (reduced-resolution) image stored in the 0th IFD. The thumbnail should be stored in strips, rather than in tiles, in order to be fully compatible with TIFF 6.0 baseline readers.

The Adobe DNG version 1.1 specification claims compatibility with the (then draft) specification of TIFF/EP_1. DNG permits all TIFF/EP tags and uses explicitly some of the tags introduced in TIFF/EP, particularly in relation to support for CFA (Colour Filter Array) photometric interpretation. The DNG specification recommends (a) that the first IFD contain a low-resolution thumbnail and (b) the use of SubIFD trees, both as described in the TIFF/EP_1 specification. See DNG_1_1 for more on the relationship of DNG to TIFF/EP_1.

History  

Format specifications Explanation of format description terms


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Last Updated: Friday, 03-Jan-2014 10:17:35 EST