First, select an image to which the lens effect is going to be applied. The applet "Width" and "Height" are automatically entered when you specify the image.

You can also check "Interactive mode" box, if you would like the lens controlled by the mouse pointer.

Now define the lens' property. You set the lens size at "Lens width", which is in fact a radius of the lens in pixel. Then, define the magnification power of the lens at "Zoom factor".

A value of 0 gives no magnification, while higher values generate higher magnification effect.

This is not the case in using real world lenses. Since a lens has a spherical figure, light coming through near the edges of the lens, more or less, tends to be distorted.

There are two types of distortion parameters: (1) diagonal distortion, and (2) XY crosswise distortion.

If you want a perfect spherical distortion, set "Diagonal" value at 10 and "XY" value at 0. Otherwise, choose any value between 5 and 20 for "Diagonal"and a value between -40 and 40 for "XY", and explore the result.

Proceed to the textscroll menu if you have checked the textscroll box; otherwise go to the expert menu.