EXIF (Exchangeable Image File Format)
Image files are really data files. Most of the data tells the computer how to display the image on your screen.
Image files have additional metadata which provides details about the image file. Known as EXIF data (Exchangeable Image File Format), this metadata is particularly important. EXIF data is a standard recognised by camera manufacturers as the way to store metadata about the image file.
EXIF data describes features of the image itself and its creation. It includes the following types of data…
- The image file itself (eg. file name; image width; image length; file compression type (JPG, tiff etc); picture orientation; resolution; resolution units (inches, cm etc); date created; EXIF version…)
- The camera/lens data (camera make; model, version, serial number, makers notes…)
- Data about the image (exposure time; f/number; exposure program (aperture priority, manual etc); ISO rating; shutter speed value; exposure bias value; metering mode; flash setting; focal length; user comments; color space; custom settings, exposure mode; white balance; capture mode…)
- Personal data (author; location; contact…)
- Copyright data (copyright owner; copyright conditions etc…)
The Field types listed above are not exclusive. Any particular EXIF data in a file will depend on what the digital camera is programmed to collect. This will vary between models and manufacturers.
Other types of metadata formats beside the EXIF data may be stored in image files. For example IPTC data.
EXIF data fields are defined by the EXIF standard. There is room for interpretation about what goes into each field. And, individual camera companies have ranges of fields for their own use. There are many hundreds of fields. More detailed information on the structure and format of the known EXIF data can be found here…
EXIF Tag list .
Individual manufacturers also have their own tag lists relating to the specific EXIF data for their use. These are the tags which identify the exposure data among other things. The tag lists for two manufacturers are included below. The rest can be found listed in the ‘MakerNote’ section of the EXIF Tag list (the general EXIF schema).
Canon EXIF tag list
Nikon EXIF tag list
The EXIF standard is supported in most image files that relate to image creating equipment including JPEG/JPG, Tiff, RIFF and WAV. It also includes the ‘RAW’ file format from the major camera manufacturers. However, some image files do not support the standard. These include: JPEG2000, PNG and GIF.
The following manufacturers are known to have EXIF tag spaces reserved for their use in the EXIF schema…
Canon, Casio, FujiFilm, GE, Hasselblad, Hewlett Packard, ISL, JVC, Kyocera, Minolta, Nikon, Olympus, Leica, Panasonic, Pentax, PhaseOne, Reconyx, Ricoh, Samsung, Sanyo, Sigma, Sony
How much use manufacturers make of EXIF data varies. You should consult the EXIF data in your images to find out what is available.
Exif data can be edited and additional data added. A range of applications are available which allow users to access the data and edit it in a file. Simple edits can also be done in Windows, Mac OS X and various other operating systems. More information on accessing and editing EXIF data can be found here… EXIF Data – Understanding Your Shots
There is an example EXIF data set after the link list.
Example EXIF data
The EXIF data below has been extracted from an image taken on a Canon camera. Not all the tags in the schema are available for use by the camera. Different tags/information might be provided by an other brand of camera.
Filename - IMG_0010.CR2 ImageWidth - 5616 ImageLength - 3744 BitsPerSample - 8 8 8 Compression - 6 (JPG) Make - Canon Model - Canon EOS 5D Mark II StripOffset - 62172 Orientation - Left bottom StripByteCount - 1488300 XResolution - 72 YResolution - 72 ResolutionUnit - Inch DateTime - 2012:06:09 10:08:49 Artist - Photographer: Damon Guy - Photokonnexion Copyright - Copyright: Damon Guy [The Author] ExifOffset - 434 ExposureTime - 1/250 seconds FNumber - 8 ExposureProgram - Manual control ISOSpeedRatings - 400 ExifVersion - 0221 DateTimeOriginal - 2012:06:09 10:08:49 DateTimeDigitized - 2012:06:09 10:08:49 ComponentsConfiguration - YCbCr ShutterSpeedValue - 1/256 seconds ApertureValue - F 8.00 ExposureBiasValue - 0 MeteringMode - Multi-segment Flash - Flash not fired, compulsory flash mode FocalLength - 70 mm UserComment - SubsecTime - 55 SubsecTimeOriginal - 55 SubsecTimeDigitized - 55 FlashPixVersion - 0100 ColorSpace - sRGB ExifImageWidth - 5616 ExifImageHeight - 3744 InteroperabilityOffset - 42296 FocalPlaneXResolution - 3849.21 FocalPlaneYResolution - 3908.14 FocalPlaneResolutionUnit - Inch CustomRendered - Normal process ExposureMode - Manual White Balance - Manual SceneCaptureType - Standard GPS information: - GPSVersionID - 188.8.131.52 Maker Note (Vendor): - Macro mode - Normal Self timer - Off Quality - RAW Flash mode - Not fired Sequence mode - Continous Focus mode - AI Servo Image size - Large Easy shooting mode - Manual Digital zoom - None Contrast - Normal Saturation - Normal Sharpness - Low , -32769 ISO Value - 32767 Metering mode - Evaluative Focus type - Auto AF point selected - Exposure mode - Manual Focal length - 70 - 200 mm (1 mm) Flash activity - Not fired Flash details - Focus mode 2 - 65535 Auto ISO - 100 Base ISO - 400 White Balance - Cloudy Sequence number - 0 Flash bias - 0 EV Subject Distance - 0.00 Image Type - Canon EOS 5D Mark II Firmware Version - Firmware Version 1.1.0 Owner Name - Damon Guy - Netkonnexion Camera Serial Number - 1030710662 (3D6F25990) Sharpness (EOS 1D) - 18 Directory index (EOS 450D) - 0 File index (EOS 450D) - 426 File number - 000 - 0000 Sharpness (A0) - 3 Thumbnail: - JpegIFOffset - 44448 JpegIFByteCount - 17723