EXIF data

EXIF (Exchangeable Image file Format) is a standard created by Japanese Electronic Industry Development Association (JEIDA) for the storage of camera and image information within JPEG and TIFF image files. See more on the detail of the format here. Most modern digital cameras now use this standard format to store information in the image files they produce. The information stored can include:

• Information about the camera that took the image (e.g.: make, model).
• The camera settings at the time the image was taken.
• The picture taking conditions at the time a image was taken.
• The location and orientation of the camera.
• Descriptive comments or audio recording added by the photographer.

To set up custom mappings for some tags you may need to translate hexadecimal numbers to decimal and the FAQ has provided a simple hex/dec calculator for you.

You should understand that EXIF is an evolving standard. As is all too common with emergent technologies, vendors are constantly adding their own variations - even between different models of their own products! In this context, programs like Portfolio have to play catch up, so do remember to register your software so that you're informed of updates and new filters.

EXIF tends to be created in files of one of three formats- 'Raw', TIFF and JPEG; it is also supported in Photoshop PSD as of v7.x and you should expect support in other formats to grow over time:

• 'Raw' files are generally maker/model specific and a few have started to gain visibility as formats, such as Nikon's 'NEF' and Canon's 'CRW', Kodak 'DCR', etc. The term 'raw' is used as, in essence, they take the exact output of the camera CCD device and store it unaltered - usually in a format based on the TIFF format. Being unaltered, this format has some popularity as it is effectively a digital negative.
• TIFF files. These give lossless compression, i.e. they decompress to the same quality as when last saved as no information is discarded in the save process. The format is an open standard, allowing for a degree of customisation (e.g. some 'raw' files) and for custom 'tags' to be created to hold information. This is how EXIF data is stored in the file.
• JPEG files. These are the most common format for files with EXIF data - especially for non-pro level digital cameras. This is because the compression achieved allows more efficient use of limited storage available in the camera. This comes at the cost of 'lossy' compression, that is information is discarded in the compression process during saving the file - this information cannot be recovered later. An added factor to consider is that every time a JPEG is re-saved the compression occurs and further information is discarded, eventually leading to visible degradation of the image.

Is there a cross-platform EXIF tool? I've only found one - "EXIFutils". This is a command line utility set and so not for the WYSYWIG folk. However, it supports Windows, Unix, Linux and Mac OSX. At present the author is working on adding IPTC support. For Windows-only users check out IMatch - this is a single user window image database. The author has created quite extensive support for RAW file, scripting, EXIF etc. The app is less $50 US and could be a useful tool for a Portfolio admin dealing with digital images and EXIF/IPTC based into. for Mac users the picture is less clear but iView has EXIF/IPTC support and is AppleScriptable; for EXIF write support you'd want the $90 US 'Pro' version.

Question: EXIF data [FAQ00324.htm]
Last Update:- 31 May 2006

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