Metadata or Meta-data is data (information) about data (in this case, image files.) Modern digital cameras (as well as other digital recording devices) usually store technical information within files created by the device (i.e. digital cameras or cam-corders.) The ‘native’ information is typically related to the creation of the files captured by the device (i.e. for a digital camera, the date, time, and exposure settings for an image at the time of capture – dates will reflect the internal settings of the camera so they may not be accurate.) For a digital camera, this data is typically referred to as EXIF data.
Exchangeable Image File Format (EXIF)
Exchangeable Image File Format (EXIF) is a part of the file structure commonly used for image storage. It has become a standard within the JPEG (and other) common image file formats. EXIF data may include all of the data types listed below as well as other data specific to a manufacturer’s equipment:
- Device Make and Model
- Date and time of capture
- Shutter Speed
- Special device-specific settings (i.e. program modes)
- F-Stop and Aperture values
- ISO setting
- Focal length of lens
- Flash information
- Type of metering used
- Pixel dimensions and image orientation (i.e. portrait or landscape)
- GPS coordinates (either from a built-in, externally attached GPS device or added during post-processing)
- Colorspace and light source information
- other manufactuer specific image information
- custom data (configured within the device, i.e. an embedded copyright statement)
All of the above data can be quite helpful when reviewing images – which camera settings work ‘best’ for the captured scene types? what are the limits for this camera? (which settings border on the limits of what can be done with the device? creating a sequential/time-based slide show, etc.)
Other data
Other types of data are typically added during the post-processing of the files. For instance, as a photographer I will add contact information, descriptive information about the scene including location and events as appropriate, rights management information (for viewers interested in commercial use of images), and other appropriate information. New operatings systems now provide relatively easy viewing of some of this information (i.e. using the Windows/Vista File Explorer and ‘turning on’ the extended attributes tabs.)
Editing Photo Metadata
Using tools like Adobe Lightroom, Adobe Bridge and other programs you can edit (or remove this information from your image files.) You should consider including basic contact information that you release in electronic form – in some case, web photo-sharing sites will add/edit this information when you upload images; in all cases I suggest that you include copyright information for images that are distributed via digital means (web pages, CD/DVD or other media.)
Meta-data tools for Linux – ImageMagick
OVERVIEW
ImageMagick®, is a software suite to create, edit, and compose bitmap images. It can read, convert and write images in a variety of formats (about 100) including GIF, JPEG, JPEG-2000, PNG, PDF, PhotoCD, TIFF, and DPX. Use ImageMagick to translate, flip, mirror, rotate, scale, shear and transform images, adjust image colors, apply various special effects, or draw text, lines, polygons, ellipses and B\[’e]zier curves.
ImageMagick is free software delivered as a ready-to-run binary distribution or as source code that you can freely use, copy, modify, and distribute. Its license is compatible with the GPL. It runs on all major operating systems.
ImageMagick is primarily a set of command line tools (but there are several GUI interfaces) which provide the means for converting, adjusting and pulling information out of digital image files.
Note that this image information is flagged with ‘rights managment’ in the sample output below using the (Linux/ImageMagick) identify command:
identify -verbose sara-test.jpg
Image: sarah_6264-0806-2008.jpg
Format: JPEG (Joint Photographic Experts Group JFIF format)
Class: DirectClass
Geometry: 3300×2550+0+0
Type: TrueColor
Endianess: Undefined
Colorspace: RGB
Depth: 8-bit
Channel depth:
Red: 8-bit
Green: 8-bit
Blue: 8-bit
Channel statistics:
Red:
Min: 0 (0)
Max: 255 (1)
Mean: 135.414 (0.531036)
Standard deviation: 75.4208 (0.295768)
Green:
Min: 0 (0)
Max: 255 (1)
Mean: 138.12 (0.541646)
Standard deviation: 68.4699 (0.26851)
Blue:
Min: 0 (0)
Max: 255 (1)
Mean: 116.812 (0.458087)
Standard deviation: 80.3365 (0.315045)
Rendering intent: Undefined
Resolution: 300×300
Units: PixelsPerInch
Filesize: 4.99105mb
Interlace: None
Background color: white
Border color: rgb(223,223,223)
Matte color: grey74
Transparent color: black
Page geometry: 3300×2550+0+0
Dispose: Undefined
Iterations: 0
Compression: JPEG
Quality: 99
Orientation: Undefined
Properties:
Exif:ResolutionUnit: 2
Exif:XResolution: 300/1
Exif:YResolution: 300/1
Jpeg:colorspace: 2
Jpeg:sampling-factor: 1×1,1×1,1×1
Photoshop:LegacyIPTCDigest: C95D651F1F7312FDDF1C37B595F55829
Rdf:about:
Signature: e18c62be76d4448795f825acc7547e55a7879581bedcd0396a0f3bf3ca9341ca
Tiff:Orientation: 1
XapRights:Marked: True
XapRights:WebStatement: DER_08062008_6264_forsyth_fount_scb: http://www.dalereagan.com/
Xmlns:dc: http://purl.org/dc/elements/1.1/
Xmlns:photoshop: http://ns.adobe.com/photoshop/1.0/
Xmlns:tiff: http://ns.adobe.com/tiff/1.0/
Xmlns:xapRights: http://ns.adobe.com/xap/1.0/rights/
Profiles:
Profile-8bim: 126 bytes
Profile-exif: 72 bytes
Profile-icc: 3144 bytes
IEC 61966-2.1 Default RGB colour space – sRGB
Profile-xmp: 2962 bytes
Artifacts:
Verbose: true
Tainted: False
User time: 0.540u
Elapsed time: 0:02
Pixels per second: 8.02517mb
Version: ImageMagick 6.3.8 04/23/08 Q16 http://www.imagemagick.org
If you are a digital photographer in Savannah and need assistance with your gear then please note that I do offer one-on-one training – please use the contact form on this site to request more information.
