See Panzer Elite for more on this.
The German optics were far superior to the Allied optics. They had a magnified view, where the Allied units did not. The Shermans had a simple, 2D elevation system, with a different crosshair at several elevations, graduated by distance.
For a "rangefinder", the German tanks had a series of triangles that represented 1 or 3 mils. With the range manually set at 1km, you would use these triangles as guides to size up enemy units and guess their ranges (from what I hear, the width of a thumb at arm's length was a good guide to use when you didn't have your head stuck in the sight).