Metadata, by definition, is data about data. Every image that comes from a digital camera already has some metadata assigned to it, normally in the form of Exif data. This is information about the image that is supplied by the camera i.e. make, model, shutter speed, aperture, ISO etc. This is just the beginning though. A digital image file can theoretically contain an unlimited amount of metadata. The most common examples of this metadata are category, keywords, location, city, state and country. We will look at these and others to help make your image collection as searchable as possible.
So what is search ability and why is it important? In short, search ability is how effective a simple image search is. If you do a search for sunsets in your image collection and only 10 of a possible 50 sunset images are found, then you have a search ability problem. If you cannot find all the sunset images in your collection, how would you know you are showing your client the best samples? Simple, you won't know and your image collection will immediately lose some of its value.
What follows is a broad outline of a key wording strategy that will add value to your image collection. It is based on a pyramid system. A particular image can only contain one reference to the top level of the pyramid. As we move down the pyramid the instances of the levels in an image, gradually increases.
The top level should be a category and location. An image can only belong to one category and similarly only be shot at one location. Examples of categories are: Architecture & Interiors, Animals, Nature (including plants and landscapes but not animals), People, Transportation etc. The main aim is that the top level descriptions should only have one instance per image.
The next level is sub-categories that relates to the main category. (I.e. cars, trains, ships and helicopters will be sub categories of the Transportation main category) An image can contain more than one instance of a sub-category. If you find yourself applying to many subcategories to an image, it's usually a sign that you don't have a wide enough distribution of main categories.
The next level should contain keywords that apply to a particular image. Here the opposite applies. The more relevant keywords you have associated with a particular image, the better your search results will be.
With this basic outline for key wording your images, it will be easy to find specific images in your catalog relating to a particular search query.