Photoshop

There are three main tools for making selections in Adobe Photoshop: the Marquee, the Magic Wand and the Lasso. The Lasso is one of those tools with several options. To reveal the different modes it offers, click on the tool and hold. The three different modes of the Lasso are freehand, polygonal and magnetic.

The Histogram panel in Adobe Photoshop CS4 (Window – Histogram) offers an overview of the tonal range of an image. The histogram is basically a chart which shows how many pixels are present at each luminosity value, with dark pixels on the left and lighter pixels on the right. If no selection is made, the histogram reflects all the pixels in the image. It is also possible to select just part of an image and use the histogram to examine the distribution of pixels just within the selected area. If the image consists of multiple layers, Photoshop displays a pop-up menu which allows you to choose either “Entire Image” or “Selected Layer” to determine which pixels are included in the output shown in the histogram.