Zooming an image feature with an enhancement

To calculate an enhancement, image statistics are used. In images acquired with the same sensor, digital numbers (DN) can vary because of land cover or environmental changes in the scene. Enhancements are based on statistics from each image. Therefore, the effects of an enhancement can vary among different images acquired with the same sensor.

For example, RADARSAT images are stored in 16-bit unsigned channels supporting a dynamic range from zero to 65,535 DNs. The usable image values in the radarsat.pix file are zero to 30,000 digital numbers. The image appears dark, with no enhancement, because it uses less than half of the available range.

When Focus collects statistics for applying an enhancement, the Tail Trim command omits the upper and lower two percent of the image histogram, by default.

To zoom an image feature with an enhancement

In the view pane, click on or near the feature you want to zoom.
On the Zoom toolbar, click Zoom 1:1 Image Resolution.

Note: When an image overview is set in the view pane, all image statistics are used to calculate the enhancement. An enhancement is calculated by building a histogram with the range of values available in the Focus view pane. By default, the original histogram is retained even when the data being displayed changes; for example, after panning or zooming. However, if you want the histogram to be recomputed each time the display changes, make sure the Focus options are set up to auto re-enhance grayscale and RGB layers. For more information about setting up auto re-enhance, see Automatically re-enhancing a layer when the display changes.