Jun 1 2023 Exif 3.0 released, featuring UTF-8 support

"A photograph of a pleasant beach scene with visible computer code overlaid on the image." Created by DALL-E via Bing Image Creator.
“A photograph of a pleasant beach scene with visible computer code overlaid on the image.” Created by DALL-E via Bing Image Creator.

CIPA, the Camera and Imaging Products Association based in Japan, has released version 3.0 of the Exif standard for camera data.

The new specification, “CIPA DC-008-Translation-2023 Exchangeable image file format for digital still cameras: Exif Version 3.0” can be downloaded from https://www.cipa.jp/std/documents/download_e.html?DC-008-Translation-2023-E.

Version 1.0 of Exif was released in 1995. The previous revision, 2.32, was released in 2019. The new version introduces some major changes so the creators felt it was necessary to increment the major version number.

Fully internationalised text tags

In previous versions, text-based fields such as Copyright and Artist were required to be in ASCII format, meaning that it was impossible to express many non-English words in Exif tags. (In practice, many software packages simply ignored this advice and used other character sets anyway, violating the specification.)

In Exif 3.0, a new datatype “UTF-8” is introduced, meaning that the same field can now support internationalised character sets, from Chinese to Arabic and Persian.

Unique IDs

The definition of the ImageUniqueID tag has been updated to more clearly specify what type of ID can be used, when it should be updated (never!), and to suggest an algorithm:

This tag indicates an identifier assigned uniquely to each image. It shall be recorded as an ASCII string in hexadecimal notation equivalent to 128-bit fixed length UUID compliant with ISO/IEC 9834-8. The UUID shall be UUID Version 1 or Version 4, and UUID Version 4 is recommended. This ID shall be assigned at the time of shooting image, and the recorded ID shall not be updated or erased by any subsequent editing.

Guidance on when and how tag values can be modified or removed

Exif 3.0 adds a new appendix, Annex H, “Guidelines for Handling Tag Information in Post-processing by Application Software”, which groups metadata into categories such as “structure-related metadata” and “shooting condition-related metadata”. It also classifies metadata in groups based on when they should be modified or deleted, if ever.

Category

Description

Examples (list may not be exhaustive)

Update 0

Shall be updated with image structure change

DateTime (should be updated with every edit), ImageWidth, Compression, BitsPerSample

Update 1

Can be updated regardless of image structure change

ImageDescription, Software, Artist, Copyright, UserComment, ImageTitle, ImageEditor, ImageEditingSoftware, MetadataEditingSoftware

Freeze 0

Shall not be deleted/updated at any time

ImageUniqueID

Freeze 1

Can be deleted in special cases

Make, Model, BodySerialNumber

Freeze 2

Can be corrected [if wrong], added [if empty] or deleted [in special cases]

DateTimeOriginal, DateTimeDigitized, GPSLatitude, GPSLongitude, LensSpecification, Humidity

Collaboration between CIPA and IPTC

CIPA and IPTC representatives meet regularly to discuss issues that are relevant to both organisations. During these meetings IPTC has contributed suggestions to the Exif project, particularly around internationalised fields and unique IDs.

We are very happy for our friends at CIPA for reaching this milestone, and hope to continue collaborating in the future.

Developers of photo management software understand that values of Exif tags and IPTC Photo Metadata properties with a similar purpose should be synchronised, but sometimes it wasn’t clear exactly which properties should be aligned. IPTC and CIPA collaborated to create a Mapping Guideline to help software developers implement it properly. Most professional photo software now supports these mappings.

Complete list of changes in Exif 3.0

The full set of changes in Exif 3.0 are as follows (taken from the history section of the PDF document):

  • Added Tag Type of UTF-8 as Exif specific tag type.
    • Enabled to select UTF-8 character string in existing ASCII-type tags
  • Enabled APP11 Marker Segment to store a Box-structured data compliant with the JPEG System standard
  • Added definition of Box-structured Annotation Data
  • Added and changed the following tags:
    • Added Title Tag
    • Added Photographer Information related Tags (Photographer and ImageEditor)
    • Added Software Information related Tags (CameraFirmware, RAWDevelopingSoftware, ImageEditingSoftware, and MetadataEditingSoftware)
    • Changed Software, Artist, and ImageUniqueID
    • Corrected incorrect definition of GPSAltitudeRef
    • GPSMeasureMode tag became to support positioning information obtained from GNSS in addition to GPS
  • Changed the description support levels of the following tags:
    • XResolution
    • YResolution
    • ResolutionUnit
    • FlashpixVersion
  • Discarded Annex E.3 to specify Application Software Guidelines
  • Added Annex H. (at the time of publication) to specify Guidelines for Handling Tag Information in Post-processing by Application Software
  • Added Annex I.and J. (both at the time of publication) for supplemental information of Annotation Data
  • Added Annex K. (at the time of publication) to specify Original Preservation Image
  • Corrected errors, typos and omissions accumulated up to this edition
  • Restructured and revised the entire document structure and style

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