The digiKam main window has a sidebar at the right border providing important information and actions of the selected images. This same sidebar is also available in the Image Editor view. It can be displayed by respectively clicking on one of the five tabs:
Properties : File and image properties, key shooting parameters.
Metadata : EXIF, Makernotes, IPTC and XMP data.
Colors : Histograms and embedded ICC profiles.
Maps : Marble widget shows GPS location.
Captions : Comments, Date & Time setting, Rating, Tags.
Tag Filters : Tag filters applied to main window selection.
Tools : An optional contextual view dedicated to group by categories all main tools available.
Clicking successively onto the same tab will make the sidebar pop up or fold back into the border.
The properties sidebar shows the essential information about the selected image which are largely self-explanatory. It is grouped into the following sections:
File Properties: these are file system related information
Image Properties: shows the image and format properties like dimension, compression, color-depth, etc.
Photograph Properties: shows a summary of the most important parameters when taking the photograph. These data are taken from the EXIF or XMP data fields if available.
digiKam Properties: optional view to show a summary of the most important captions values set in digiKam database.
Metadata are data about the images or files, like technical data of camera setting during shooting, author info, copyrights, keywords, captions, and coordinates of location.
The metadata sidebar is composed of four sub tabs EXIF, Makernote, IPTC and XMP data. On the left, two buttons let you choose between full and simplified data display. In the middle you will find a disk icon to save the metadata to the disk. Next to it are a printer and copy icon - they do just that: print or copy the respective tab metadata to the clipboard.
A really nice feature is the live search box on the lower end of the metadata tabs. As you type in a keyword, the metadata on top of it will be successively filtered until you narrow down and what you are looking for. It is a quick way of accessing specific information.
Metadata, as shown in these four tabs, can be modified and enhanced in a number of ways elsewhere:
EXIF stands for Exchangeable image file format. It was designed specifically for digital cameras. It allows a large amount of information about the photograph to be stored. This information describes the camera which took the image along with the settings (including date and time) in use when the image was taken. An in-line thumbnail can be included.
EXIF format contains a set of marker sections named Image File Directories (IFD). The sections likely to be found in a normal EXIF file are as follows:
Image Information: contains general information about the image.
Embedded Thumbnail: contains information about the embedded thumbnail image.
Photograph Information: contains extended information about the photograph.
Interoperability: contains information to support interoperability between different EXIF implementations.
You can review embedded EXIF information for the selected image from the first sidebar tab. The EXIF Viewer is purely informational: nothing you do with it will cause any change to the EXIF sections. If there are more entries than space available, just scroll down with the mouse wheel.
You can use two different levels to display EXIF marker sections:
Simple: display only more important EXIF marker for photograph.
Full: display all EXIF markers.
Some vendors add additional EXIF sections, such as Canon, Fujifilm, Nikon, Minolta, and Sigma. These sections contain vendor and model specific notes. These will be displayed on the Makernote tab.
The EXIF standard defines a Makernote tag, which allows camera manufacturers to place any custom format metadata in the file. This is used increasingly by camera manufacturers to store a myriad of camera settings not listed in the EXIF standard, such as shooting modes, post-processing settings, serial number, focusing modes, etc. but this tag format is proprietary and manufacturer specific.
The International Press Telecommunications Council, is a consortium of the world's major news agencies and news industry vendors. It develops and maintains technical standards for improved news exchange that are used by virtually every major news organization in the world.
The IPTC was established in 1965 by a group of news organizations to safeguard the telecommunications interests of the world's press. Since the late 1970s IPTC's activities have primarily focused on developing and publishing industry standards for the interchange of news data.
In particular, the IPTC defined a set of metadata attributes that can be applied to images. These were defined originally in 1979, and revised significantly in 1991 to be the "Information Interchange Model" (IIM), but the concept really advanced in 1994 when Adobe defined a specification for actually embedding the metadata into digital image files - known as "IPTC headers".
The colors sidebar has two sub tabs Color and ICC Profile. Here are more details about Color Management
The histogram for an image shows the amount of each color that is present and their different amplitudes within the image. If your photograph has a color cast you might be able to see what is wrong by looking at the histogram.
The Histogram Viewer shows the statistical distribution of color values in the current image. It is purely informational: nothing you do with it will cause any change to the image. If you want to perform a histogram based color correction, use the Adjust Levels or Adjust Curves Image Editor plugin.
An image can be decomposed into Red, Green, Blue, Alpha color channels. Alpha channel is a Layer in the image that supports transparency (like PNG or GIF images). Each channel supports a range of intensity levels from 0 to 255 (integer valued). Thus, a black pixel is encoded by 0 on all color channels; a white pixel by 255 on all color channels. A transparent pixel is encoded by 0 on the alpha channel; an opaque pixel by 255.
The Histogram Viewer allows you to view each channel separately:
Luminosity: shows the distribution of brightness values.
Red, Green, Blue: show the distribution of intensity levels for the Red, Green, or Blue channels respectively.
Alpha: shows the distribution of opacity levels. If the layer is completely opaque or completely transparent, the histogram will consist of a single bar on the left or right edge.
Colors: shows the Red, Green, and Blue histograms superposed, so that you can see all of the color distribution information in a single view.
With Scale option, you can determine whether the histogram will be displayed using a linear or logarithmic Y axis. For images taken with a digital camera, the Linear mode is usually the most useful. However, for images that contain substantial areas of constant color a Linear histogram will often be dominated by a single bar. In this case a Logarithmic histogram will be more useful.
You can restrict the analysis of the Statistics field shown at the bottom of the dialog to a limited range of values if you wish. You can set the range in one of two ways:
Click and drag the pointer across the histogram display area, from the lowest level to the highest level of the range you want.
Use the spin button entries below the histogram area. Left entry is bottom of range and right entry is top of range.
The statistics shown at the bottom of the Histogram Viewer describe the distribution of channel values, restricted to the selected range. These are:
The number of pixels in the image.
The number whose values fall within the selected range.
The standard deviation.
The median of the selected histogram portion.
The percentage whose values fall within the selected range.
The color depth of the image.
Alpha channel in the image.
The source of the histogram, either Full Image or Image Region if you have selected an area of the image in the Editor.
Histograms are a graphical means to assess the accuracy of an image shown on the screen. The graph represents the 3 regions of the photograph brightness:
(1) : the shadows-tone on the left.
(2) : the middle-tone on the middle.
(3) : the highlights-tone on the right.
The distribution of the graph, where the spikes and bulges are clustered, indicates whether the image is too dark, too bright, or well-balanced.
With an under exposed photograph, the histogram will have a distribution of brightness that tends to be mostly on the left of the graph.
With an over exposed photograph, the histogram will have the bulge showing the brightness distributed mostly towards the right of the graph.
With a correctly exposed photograph, the histogram will have a distribution of brightness that will be most prominent near the center part of the graph.
Important: not all photographs have to exhibit this bulge in the center part of their histogram. Much depends on the subject of the photograph. In some cases, it might be appropriate for the histogram to show a peak at one end or the other, or both.
The histogram is a reliable way of deciding whether or not a photograph is correctly exposed. Should the histogram show an over or under exposure, an Exposure Correction Tool should be used to fix the photograph.
This tab is based on the world-map widget to display a rough map of orientation. You can zoom in and out with the mousewheel by either scrolling it or hold and drag it. Pan by holding down the left mouse button.
The left sidebar is a geo-search tool. Press the Ctrl-left mouse button to pull-up a square as indicated. All images falling within the coordinates of that square will be shown.
On the right sidebar you will find a cross to indicate the GPS location and the selected image's name next to it. The GPS coordinates and the time information are displayed below the widget.
For higher resolution maps choose button to open the detailed map service (choose before on the left scroll box) in a Internet browser.
The displayed positioning data are actually stored in the image's EXIF tags (and not yet in the database). That allows the location to be read by any other application that can understand EXIF GPS data.
The Global Positioning System usually called GPS, is the only fully functional satellite navigation system. A constellation of more than two dozen GPS satellites broadcasts precise timing signals by radio, allowing any GPS receiver to accurately determine its location (longitude, latitude, and altitude) anywhere on Earth. GPS also provides an extremely precise time reference and gauge speed with a very high degree of accuracy.
GPS information can be stored in images directly by supported cameras or by synchronizing photographs with an external GPS device track. Look at this section for more information.
This sidebar tab serves to apply and edit image attributes like captions, rating, date and tags. The attributes are stored in the associated database, in the IPTC and EXIF data fields and become part of the image. All attributes are accessible in one sidebar view as shown in the screenshot below. During image reading the order of priority is a) database b) IPTC and c) EXIF. So if there is a discrepancy between any of the three, this priority will take effect and a synchronization will take place. This sidebar has a first-previous-next-last arrow navigator field on top if shown in the main application.
The caption view can be used to type or paste in a caption of unlimited size (see note below). The text is UTF-8 compatible, meaning that all special characters are allowed. The captions are copied to EXIF and IPTC fields to be used by other applications.
IPTC data only supports ASCII characters and is limited to 2000 characters (old American norm). All texts will be truncated after 2000 chars, and special characters will be malformed. If you intend to use the IPTC caption field in other applications you should be compliant with these restrictions.
After commenting, either choose the button or go straight to the next image, the captions will be saved.
Next to the Apply button there is the button. From it you can either choose to read metadata from the selected file to the database, or the other way around, to write metadata to the files (the latter take place anyway if you chose a metadata setting so that all metadata is always saved to the images).
In the Date & Time section, which reflects the time of taking the photograph, you can change all values. From the date combo-box a calendar opens, and the time setting spin-box can also be written by directly typing the time. The dating is copied to the EXIF 'Date and Time' field. If you need to change a number of images for their creating time & date, there is a more comfortable method available in Batch Queue Manager. This latter option can be found under → . Select the images to be changed in the main view and call the plugin.
The Rating section displays a 0...5 star rating scheme that can be used in searches and sort orders. It can be applied by a single mouse click to the 5 stars in the sidebar or with a keyboard short-cut Ctrl+0...5. The rating from the sidebar is always applied to one image at a time. To rate a number of images, select them and pop-up the context menu (right-click) to apply a common rating.
The rating is then transcribed into the IPTC 'urgency' data field. The transcoding follows the scheme in this table:
|digiKam Rating||IPTC Urgency|
The tag view shows an adaptive filter tag search box, the tag tree and a combo-box containing the tags previously applied in this digiKam session.
The tag tree will be adapted dynamically as a function of the search word as you type into the box. So it is easy to quickly reduce the number of possibilities when searching for a tag. Of course, this feature is only useful if you have many tags.
The combo-box at the bottom is another ergonomic feature for easy tagging of an image series. As you apply different tags they will be memorized in this box for quick access.
Otherwise tags are simply applied by checking the respective boxes in the tree. All tags of an image are transcribed into the IPTC 'keyword' data field.
In case you have selected a number of images in the main view and you check a tag in the tag tree, this one is only applied to the highlighted image, and not to the whole selection. If you want to tag selections, refer to the Filters section.
The tag filter sidebar is used to modify the set of images displayed in the main window view. Normally one uses the left sidebar with its Album, Date, Tags and Searches view. When additionally one or more tags on right sidebar tag filter is checked, only the cross-section of these two selections will be displayed. All created tags are available.
To give an example, suppose you have a tag called 'public' which tags all images except your private ones. Then you can check this 'public' tag in the right sidebar to hide the private images (all those not having 'public' tag). Whatever view mode you chose from the left sidebar, 'public' only image will be displayed. Another typical example is the selection of a subset of tags in a hierarchical tree. Suppose you want to display 'red' and 'green' from a tag tree containing 7 different colors as sub-tags. Simply click on the 'color' tag of the main view and check 'red' and 'green' from the right sidebar.
Another use is drag-and-drop tagging. Lets say you selected in the main view a number of images to tag them. If the tag already exists, simply drag it from the right sidebar onto the selection (any one of the highlighted images). A dialog will pop-up and ask if this tag should be applied.
In the above example the main window shows the images from a calendar date, the tag filter is set to 'not tagged', which reduces the set to 3 images. They have been selected with Ctrl+a, then a tag is dragged from the right tag tree over the selection and dropped. A pop-up dialog asks if the tag shall be applied.
The tools view from right sidebar host the list of actions available to process actions on selection. The list is an icon-view sorted by categories of tools. This view give a quick preview of all actions from main menu. For example, with image editor, you can adjust size current image with relevant crop tool.