You should now be familiar enough with the basic controls of Open_EV to begin experimenting with some of the other features which the program provides. Some help files are available by clicking on the help button on the top left hand side of the screen, but if this does not work you can access the same help files at this web address http://openev.sourceforge.net/app/openevmain.html.
Use the second .img file you downloaded (Site 020 1992_reduced.img) and run through the same steps as before. You may notice that the linear stretch is more effective the the histogram equalise at detecting the archaeological anomalies for this imagery. You can alter the way that the stretches work by changing the raster preferences as shown in the dialogue below. (Click the Edit/Preferences menu button to get to the Preferences dialogue, and then click on the Raster button) Experiment by altering the Tail Trim Percentage and Standard Deviations numbers, and see the resulting changes in the way the image is displayed.