Digital Photographer's Software Guide - Bertemes - Net

3
Exif Tools
Exchangeable image file format, or Exif (commonly but not officially capitalized as
EXIF), is a file format standard that enables digital cameras to record metadata about
each photograph along with the image data. It stipulates how the image data should be
recorded—compressed files in JPEG and uncompressed files in TIFF. Image viewing
software can then extract the metadata, which may include details such as date, time,
camera model, and shutter speed, and make it available whenever the image is displayed
on a monitor.
One of the limitations of Exif data is its tendency to become corrupted during JPEG
compression. JPEG is a “lossy” format, which means it compresses the data, unlike TIFF,
yet Exif takes its method of structuring metadata from the TIFF format, placing them
within the image file itself.
In spite of its limitations, Exif does at least provide a framework in which metadata can
be stored and retrieved. In addition to the make and model of the camera, date, and
time of capture (plus location, if you have a GPS receiver connected to your DSLR),
date/time of saving after processing, and the type of post-processing software used, Exif
data may contain many other details. They can include exposure time in seconds,
f-number, exposure program used, spectral sensitivity of each channel, ISO speed, shutter
speed, subject distance, metering mode, flash/no flash, focal length, equivalent focal
length, XY resolutions, white balance mode, image gain adjustment, and so on. It is a
long list, made longer by the manufacturer’s proprietary information about, for example,
exposure programs for portraits as opposed to landscapes. Many photographers agree:
“It beats the hell out of taking notes.”