To give you complete flexibility in analyzing your FIR filter design, ScopeFIR's plots provide four different zooming modes, Wheel-Zoom, X-Zoom, Y-Zoom, and Box-Zoom*.

Wheel-Zoom

ScopeFIR's most powerful zoom mode is Wheel-Zoom, which allows you to instantly zoom in on any area of interest using the mouse wheel.  To use Wheel-Zoom:

1. Click on the frequency or impulse plot of interest.  The plot will flash briefly to show that it has input focus.  (If the plot already had focus, a vertical cursor will appear.)
2. Move the mouse to the area of interest on the plot within the rectangle defined by the axes.  For best results, try to point the mouse as closely as possible to the desired area.
3. Hold down the Ctrl key and rotate the mouse wheel away from you to zoom in.  If necessary, you can move the mouse as you rotate the wheel to refine your zoom position.
4. Release the Ctrl key.  Without Ctrl , the wheel allows you to cycle through the existing zoom levels (whether defined by the wheel or via the other modes described below): to un-zoom, rotate the mouse wheel toward you; to re-zoom, rotate the mouse wheel away again. Un-zooming stops at the top level.
5. You also can get to the top zoom level at any time by clicking on the wheel, equivalent to Zoom Top command.  Clicking the wheel again will get you to the bottom level, equivalent to the Zoom Bottom command.
6. Additional zoom levels can be defined at any time using Ctrl-wheel again.  Note, though, that all levels below the current level will get replaced by the new level.

Other Zoom Modes

ScopeFIR's other three zoom modes are activated by left-clicking the mouse and dragging it in order to define a zoom region.  ScopeFIR automatically selects the mode based on where in the plot you start your zoom action. Zooming is selected using nine the different areas of the plot delimited by the X and Y axes. The zoom selection areas are shown in the figure below:

Different zoom cursors indicate which zoom mode you are in. For the X-Zoom mode, you will see a pair of vertical cursors; for Y-Zoom mode, you will see a pair of horizontal cursors; for Box-Zoom mode, you will see a rectangular cursor.

X-Zoom

X-Zoom is probably the most useful zooming mode. In X-Zoom, the vertical range of movement of the mouse is ignored and the horizontal range of mouse movement is used to set a new zoom range. The new vertical range of the zoomed plot is set automatically or manually, according to how you have the Y-Axis configured. You specify X-Zoom by starting your zoom range above or below the main area of the plot (that is, in the Main-Title or X-Title areas.)

Y-Zoom

In Y-Zoom allows you to specify the Y-Axis range, and the plot is zoomed in the Y-Axis only. (The X-Axis range remains the same.) You specify Y-Zoom by starting your zoom range in the left or right of the range of the X-Axis.

Box-Zoom

Box-Zoom is similar to the zooming mechanism of many other programs. You specify a "zoom rectangle" by dragging a diagonal which represents two opposite corners of a rectangle. You specify Box-Zoom when you start in the central data area of the plot, or if you start in any of the four extreme corners of the plot window.

*We really should have patented this, but it's too late now!