Metadata is data about data. It is information about the image data, such as exposure time, ISO, aperture, etc. that is stored inside of the file along with the actual image data itself. Many cameras store this kind of information in the original image file that comes out of the camera. This data can usually be accessed through the camera manufacturer's software, such as Nikon View, or Canon EOS Viewer Utility. This data is stored in the EXIF (Exchangeable Image File) format that is becoming a standard in digital cameras. In addition to the camera manufacturer's software, there are many third-party programs that will also show this EXIF metadata.
A particularly nice freeware program is EXIF Reader by Ryuuji Yoshimoto. It not only shows the EXIF data contained in the file, it also is a useful thumbnail viewer. Another useful freeware program is EXIFLOG by Michal Covington which displays EXIF temperature data from DSLR cameras. Neither of the above EXIF utilities support Raw file formats however. One that does, and is very powerful but basic and run by a command line, is ExifTool by Phil Harvey. Photoshop also will display EXIF metadata. Go to File > File Info and click on "Camera Data 1".
This is just one of the multiple parts of Photoshop's File Info dialog. It displays some of the most pertinent EXIF data in an image file, but not all of it. Photoshop's File Info, however, allows you to add your own metadata information into the file under Description and all of the other categories except advanced. Adobe has implemented even more extensive and powerful metadata tools in Photoshop CS2. In the File Browser it is possible to add metadata to multiple files at once. Ian Lyons has a tutorial on File Browser and how to do this at the Computer Darkroom web site.
It is also possible to save the custom information that you have added in all of the File Info boxes as a template to use for other files. Click on the File Info menu options (the small triangle in a circle in the upper right hand corner of the File Info dialog box) and select "Save Metadata Template". Then you can load it from this menu in your next image.
Photoshop CS2 also offers the ability to create custom metadata panels in File Info. Adobe uses XMP (eXtensible Metadata Platform), a version of XML (eXtensible Markup Language), to support metadata formats. In the example seen above, FITS Liberator has created custom metadata information panels that are displayed in Photoshop CS2's File Info dialog. These panels contain data about the settings used in FITS liberator when an original FITS file is converted and a hyperbolic arcsine stretch applied (as we did to the image of M33 in the section on Advanced Image Processing of Raw Images - Non-Linear Stretch). Adobe's website has information about the implementation of metadata and XMP explained in detail as well as information about creating custom File Info panels. Not all file formats support the embedding of metadata. TIFF (Tagged Image File Format) and JPEG (Joint Photographic Experts Group) formats do, as well as Photoshop's native .PSD format. Image Information Some possible information that can be recorded and stored as metadata in an image file:
Naturally, not all of this information needs to be recorded or stored with the image, the choice is yours. |
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