Photo Metadata (EXIF/IPTC) Display
“Photo metadata” refers to two kinds of information about digital images: EXIF data and IPTC data.
EXIF (EXchangeable Image File) information provides very detailed information about the camera settings used to take the photograph. By default, JAlbum and BluPlusPlus extract and display EXIF information generated by a digital camera.
IPTC (International Press Telecommunications Council) fields were originally created for use by press photographers who needed to attach information to images when they submitted or stored images electronically. IPTC fields are capable of storing extensive information about an image, in an almost "free form” format. More information about how to generate and use IPTC information can be found here.
Where BPP displays metadata
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| Photo metadata generated with “Custom” chosen on the BPP Advanced tab (using the default value for the metaDisplayFields user variable) |
BPP can display metadata in a variety of locations:
- in a popup box that appears when the appropriate icon is clicked or when the viewer hits the ‘i’ key on the keyboard
- as a thumbnail tooltip (below a thumbnail image on an index page)
- as a thumbnail caption (below a thumbnail image on an index page)
- as a slide caption (below an image on a slide image page)
To enable the extraction of metadata from images, the ‘Extract photographic data (EXIF)’ checkbox must be checked on JAlbum’s Advanced-Metadata tab (it is checked by default).
metadata present
metadata not present
In BPP, the existence of metadata for a given image is indicated by an ‘i’ in the icon row on a slide image page; if no metadata is available, the ‘i’ is grey or has a dotted border.
When the blue ‘i’ is clicked, a yellow box containing the metadata appears.
Metadata can also be displayed in tooltips that appear when one hovers over
a thumbnail image on an index page and in a caption below the image on a slide
page.
Metadata presets available in BluPlusPlus
There is a drop-down menu on the BluPlusPlus Advanced tab that provides four preset options for which metadata fields are displayed in the generated album.
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The display mode options are chosen on the BPP Advanced tab. |
- When ‘custom’ is chosen (the default), the metadata fields specified in the meta data custom fields box are displayed.
- When ‘verbose’ is chosen, a larger number of metadata fields are displayed (these may not be user specified).
- When ‘all’ is chosen, BPP will display all metadata fields (including unknown ones) as well as full field names. This is useful to determine what metadata information is available from a particular camera.
- When ‘iptc only’ is chosen, BPP will only display IPTC fields.
‘Verbose’ and ‘all’ are useful primarily for seeing what metadata is available and what the metadata field names are.
Customizing the metadata information displayed
The metadata fields displayed when ‘custom’ mode is used are determined by the fields specified in the meta data custom fields box, on the BluPlusPlus-Advanced tab; metaDisplayFields consists of a series of metadata field names, separated by the ‘|’ character. A special ‘<title>’ tag is used to generate the bold section titles (such as ‘General Info:’, ‘Basic Shot Info:’, etc.—see above).
Many metadata field names are standard in the industry; some are specific to a particular manufacturer. Manufacturer-specific tags are usually preceeded by a prefix (e.g. Canon uses the prefix ‘Canon Makernote’). These manufacturer-specific tag names are stripped from the EXIF field names when an album is generated with either ‘custom’ or ‘verbose’ chosen; when ‘all’ is chosen, the full tag names are displayed. Generating an album with a single image using the ‘all’ setting can help determine the full tag name needed for inclusion in the meta data custom fields box.
Customizing the metadata field names displayed
By default, BluPlusPlus displays the “custom” IPTC and EXIF field names. These field names can be customized by the use of ‘photo-metadata.properties’ files.
Customizing the look of the display window
The look of the display window can be altered by changing the style css file. The appearance of the metadata display window is controlled by the photometainfo, metainfo-header, metainfo-name, and metainfo-value css selectors.
Default metadata fields displayedThe default contents of Meta Data Custom Fields is given below, formatted for easy reading (but Meta Data Custom Fields must be entered as a single string with no line-breaks). Note that text preceded by ‘<title>’ will be rendered as a bold heading.
<title>General info:|
Model| Make| Device Setting Description| <title>Basic shot info:| Date/Time| Focal Length| Subject Distance| Aperture Value| White Balance Mode| Flash| Metering Mode| Shutter Speed Value| F Number| ISO Speed Ratings| <title>Advanced shot info:| Exposure Bias Value| Exposure Time| Exposure Mode| Max Aperture Value| Brightness Value| Contrast| Saturation| Sharpness| <title>Exif-related info:| Exif Image Width| Exif Image Height |
Focal Length Calculation (note: this is an advanced topic)The focal length of a camera lens is the distance from the lens to the focal plane (either the digital sensor or the film). Knowledgable photographers are familar with the focal lengths of various 35mm SLR lenses, and from the focal length, can tell the kind of magnification involved (for example, a 140mm lens is a telephoto lens, while a 28mm lens is a wide angle lens). The actual focal length of a digital camera lens is very different from the focal length of an “equivalent” 35mm camera lens. Because of widespread familiarity with 35mm focal lengths, most photographers find it more useful to have the focal length of a digital camera lens expressed as a “35mm equivalent” rather than the actual focal length. BluPlusPlus attempts to calculate the 35mm focal length equivalent based on information stored in the EXIF data. If that data is either absent or insufficient, BPP will use camera-specific information stored in the camera.properties file (located in the root level of the BPP skin folder). This file contains conversion information for a number of popular cameras. BPP users are invited to contribute conversion information for other cameras. |
EXIF Tips and Traps
Unfortunately, many image enhancement programs (including versions of Photoshop and Photoshop Elements) alter the EXIF information when they save an image file. In particular, the camera-specific tags are often lost after the file is processed by one of these programs.
If preserving metadata information in the form created by the camera is important, be sure to use image enhancement software that does NOT alter metadata information.
A workaround for this problem is to use a program such as jhead or Exifer (see Resources page) that will save metadata information to an external file which can then be restored to the image file after an enhancement program has been used. Although jhead is a very nice piece of software, it is not particularly easy to use.
An example of display field customization
Step 1: Determine the exact metadata names for a given image
Go to the Advanced
tab of BPP and selected ‘All’ for the Meta-data Display Mode
Create an album and click the ‘i’ button to show exif/iptc information.
In this example, the following appeared:
Step 2: Organize the specific metadata you want to show in the BPP custom mode (in the desired order).
Assume that the desired metadata display is as follows:
Step 3: Prepare the properly formatted list to be inserted into the Meta-data
Custom Fields box under the Advanced tab of BPP.
Note that the metadata names appearing in this list must be EXACTLY the
names that appeared in the full dump of metadata listed above. Any extra space
in the fields will cause BPP to not see those fields. The following is the listing
for the custom metadata fields:
|<title> Image Information:|Canon Makernote.Owner Name|Exif Image Width|Exif Image Height|Date/Time Original|<title> Location Information|Iptc.City|Iptc.Province/State|Iptc.Country/Primary Location|<title> Camera Settings:|Model|Canon Makernote.Iso|Aperture Value|Exposure Time|Canon Makernote.Macro Mode|Canon Makernote.Flash Mode|Canon Makernote.White Balance|Focal length
Step 4. Customize the way the metadata field names get listed on the BPP slide
page.
Some of the field names are awkward. They can be changed by adding
the following to the photo-metadata_en.properties file located in the BPP texts
file:
Canon Makernote.Owner Name=Photographer
Iptc.City=City
Iptc.Province/State=State
Iptc.Country/Primary Location=Country
Exif Image Width=Image Width
Exif Image Height=Image Height
Date/Time Original=Date/Time
Model=Camera Model
Canon Makernote.Iso=ISO Value
Exposure Time=Shutter Speed
Canon Makernote.Macro Mode=Macro/Normal Mode
Canon Makernote.Flash Mode=Flash Mode
Canon Makernote.White Balance=White Balance
This results in the following EXIF/IPTC display: