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 digiKam Image Editor (except the Filters tab). It can be displayed by respectively clicking on one of the eight 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, Labels, Rating, Tags, selected metadata.
Versions : Image history.
Filters : Filters to apply 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 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 for example Color Balance, Levels Adjust or Curves Adjust in the Image Editor.
An image can be decomposed into Red, Green and Blue 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 the 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 in 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.
digiKam offers three geolocation tools:
The Map View on the Left Sidebar which is the search tool for finding images by their GPS data.
The Geolocation Editor which is accessible via → (Ctrl+Shift+G) and allows to set and to edit GPS data.
This tab on the Right Sidebar which shows the location of the image on a map and is purely informative.
All three are based on the Marble widget.
This tab shows a map of orientation where you will find a marker or a thumbnail to indicate the GPS location of the selected image. The GPS coordinates and the time information are displayed below the widget. You can zoom in and out with the mouse wheel by either scrolling it or hold and drag it. Pan by holding down the left mouse button.
For navigating on the map refer to Marble handbook, Chapter 2. The meaning of “GPS” and functions and buttons that apply to all three geolocation parts are described in the Geolocation Editor chapter of this handbook. This applies to the context menu on the map and the line of buttons under the map except the last one.
For information about the different map services you can use the drop-down field under the line of buttons. Choose a service here and then click the See-more-information-on-the-Internet button to the right.
The displayed positioning data are actually stored in the image's EXIF tags. That allows the location to be read by any other application that can understand EXIF GPS data.
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 Versions tab shows the history and the saved versions of a photograph. With the three buttons in the top right corner you can choose between a simple list of the saved versions, a tree view and a combined list that shows the versions together with the actions performed with the selected photograph.
The tree view shows the parent and child versions of the selected image. Here the second and the fifth version derive directly from the original image, the third and forth version are children of the second version.
The combined list shows the versions together with the actions/filters applied to them. Here the second version was created by resizing the original, applying the unsharp mask, correcting the white balance and finally adding a frame with the border tool. The child versions are grouped in Derived Versions and Related Versions. Related Versions arise if you modify the original and save the changes with Save As New Version.
To learn how to control what is stored as a separate version and which versions are displayed in the Image Area see Image Versioning Settings.
The Filters tab is used to limit the set of images displayed in the Image Area. Normally one uses the Left Sidebar with its different views to confine the images displayed for example to the content of an album or to images with a certain label assigned to them. The Filters tab on the Right Sidebar offers a number of filters and if one of these are filled in, selected or checked only the cross-section of these two selections will be displayed in the Image Area.
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, only 'public' images 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.
You can also use a combination of the filters but here we have to look a little bit closer: The main filters and also the different types of labels in the Labels Filter (color, pick, rating) are connected with boolean AND which means that all selected filters have to fit for the images to be displayed. If you select 'JPG' in the MIME type filter and 'red' in the labels filter only those photographs from the selection on the Left Sidebar will be displayed that have JPG format AND are labeled 'red'.
On the other hand the tags in the tag filter and the individual labels within one type of labels are connected with boolean OR as you might have noticed already in the public/private example above. That means if you check more than one tag in the Tags Filter all images with at least one of these tags applied will show up (as long as they are not ruled out by one of the other filters).
Another use of this tab of the Right Sidebar is drag-and-drop tagging. Lets say you chose with the help of the Left Sidebar a number of images to tag them and they are now displayed in the Image Area. If the tag already exists, simply drag it from the Right Sidebar onto one of the icons. A dialog will pop-up and ask if this tag should be applied to this item only, to all items or, if there is more than one icon selected (highlighted), to the selected items.
In the above example the main window shows the images from a calendar date, the tag filter is set to 'Oldtimer', which reduces the set to 3 images. In the Text Filter I typed “Funeral” which leaves only one picture of the only funeral car oldtimer in my collections. Then a tag is dragged from the Tag Filter over the icon and dropped. A pop-up dialog asks if the tag shall be applied to this item only or to all (displayed) items.
Note that the Text Filter has a little drop-down menu to select which image information should be included in the search and the rating group in the Labels Filter has one to choose whether you want a certain rating or a range.
The tools view from right sidebar hosts 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 the Image Editor, you can adjust the size of the current image with the relevant crop tool.