Digital Learning > Digital Image Basics
Understanding Digital Image Terminology and
Technology
A solid understanding of the terminology and concepts associated with digital imaging can improve the results of your digital image preservation and sharing activities.
Digital Imaging Activities
To understand digital image technology, it useful to consider four distinct categories of activities.
Capturing
- Digital images are typically captured by scanning an existing
image, or by creating a new one with a camera. In both cases,
sensors record image information at an adjustable level of detail for
such image attributes as color, hue, and contrast.
Editing
- With the use of digital image editing and management software,
one can make useful and quick adjustments to color, contrast, brightness
and other image attributes. In addition to these adjustments,
non-professionals often use image editing software such as Adobe Photoshop Elements 7
Filing
- The captured image information must then be formatted and filed digitally
for archiving or future use. This entails a choice
of digital image formats and labeling/indexing schemes.
Sharing / Displaying - The image information previously captured and stored is then available to be displayed and shared in a relatively broad range of ways. Sharing activities include email attachments, web display, and printing. Further possibilities include online albums and share sites, photo books, and self managed websites.
There are distinct relationships between these activities, and decisions made in one activity will impact the range of options available in other activities.
For example, a decision to set a scanner at a particular resolution will impact the amount of image information to be saved and the level of detail available for print enlargements. The selection of a file format will impact the required storage space necessary for the related file and the quality of the information. All of the prior decisions will impact the maximum size image you may print at a "high quality" level of print resolution.
This article is focused on de-mystifying some basic terminology, and providing a sense for how the activities relate. Specific "How To" guides can be accessed via the menu to the left.
Digital Image Capture Basics
Digital images are most often captured/created by cameras or scanners as tiny squares of image information called pixels (short for picture elements). The technology of these sensors is not important to us, but an understanding of the form and shape of the information captured is useful.
Digital image information is recorded as a grid consisting of columns and rows of pixels. The information about each pixel is recorded as a shade and hue of the colors red, green, and blue (RGB). The number of rows and columns of squares (total pixels) recorded is a function of the maximum pixel capability of the equipment used and the settings selected by the user.
Typically, the price of equipment increases with higher pixel capture and resolution ratings for cameras or scanners. However, as discussed in other articles, much of the equipment available today provides capacity well beyond our typical needs.
To better understand the impact of pixel counts, look for a nearby object of roughly 10" by 10" and try to picture it within a grid of 100 squares consisting of 10 rows and 10 columns. If color, hue, and other information for each 1 inch square were to be averaged and recorded, a reconstruction of the image information would be vague and blurred.
On the other hand, if the same 10" x 10" image information is recorded in a grid of 1,000 rows by 1,000 columns, the info would now be reflected as information about 1 million picture elements (pixels), and the reconstruction of the image would reflect considerably more detail / resolution.
In the case of a digital camera, you are allowed to set the number of pixels/squares of information of detail to be captured for a given image, up to the maximum megapixel (million pixels) rating of the camera. In the case of a scanner, you are allowed to set the pixels per inch (PPI) of the actual object to be scanned, up to the maximum PPI rating of the scanner.
Knowing that you have control over the number of pixels to be captured, and the math of how this will impact your digital files and potential uses of the images is important to planning your image preservation and sharing projects.
