This is especially helpful if you are scanning films of different sizes. When the Autosize box is checked, the ROI specified in the Preview Area is ignored. Instead the film guides are used to detect the width of the film. The Top Center option moves the ROI to the top and center of t he maximum scan area. This is where the film guides place the pieces of film smaller than the maximum scan area.
Landscape means the top and the bottom are longer than the sides.
You can adjust the ROI by changing the values in these boxes. If you adjust the ROI in the Preview Area , you will see the values change in the Dimension Boxes .