From Digital Imaging

Selection tools and techniques

One of the most skilled areas of digital retouching and manipulation is the ability to make accurate selections of pixels for repositioning, modifying or exporting to another image. This skill allows localised retouching and image enhancement. Obvious distortions of photographic originals are common in the media but so are images where the retouching and manipulations are subtle and not detectable. Nearly every image in the printed media is retouched to some extent. Selections are made for a number of reasons:

  • Making an adjustment or modification to a localised area, e.g. colour, contrast etc.

  • Defining a subject within the overall image to move or replicate.

  • Defining an area where an image or group of pixels will be inserted ('paste into').

Three categories of selection tools are available for selecting groups of pixels in very different ways. These categories are:

  • The 'marquee tools' select pixels by drawing a rectangle or elliptical shape around an area within the image.

  • The 'lasso tools' are used to draw a selection by defining the edge between a subject and its background.

  • The 'magic wand' selects groups of pixels by evaluating the similarity of the neighbouring pixel values (hue, saturation and brightness) to the pixel that is selected.

Tools, palettes and options

At the top of the tool palette in Photoshop are the selection, crop and move tools. Some tools in Photoshop are hidden.

To select a tool you can:

  1. Select the visible tool by clicking its icon.

  2. Click on...

Products & Services
Video Cameras
Video cameras record live-action scenes that are available for viewing via a stored or transmitted video feed. This allows the user to create a permanent and detailed chronicle of events. Video cameras record dozens of pictures (or frames) a second that when viewed in succession, clearly distinguish the translation of an object or person over time.
CCD Image Sensors
Charged coupled device (CCD) image sensors are electronic devices that are capable of transforming a light pattern (image) into an electric charge pattern (an electronic image).
Edge Finders
Edge finders locate the edge of a workpiece during machine setup operations. Edge finders can be simple, mechanical tools or electrically activated devices.
Low Light Cameras
Low light cameras are a type of video camera with extreme photon sensitivity, and are excellent for recording in situations where only ambient levels of light are available. Common deployments include overnight surveillance and remote machine monitoring.
Fiberscopes are flexible borescopes that use fiber optic technology, an eyepiece at one end, and a lens at the other to inspect bores and cavities. They house fiber optic bundles in a flexible tube that allows users to change the viewing angle or navigate curved paths.

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