Zoom ratio is the proportion of magnification change that is possible by changing the setting on the zoom body. For the DRV N25 this is 25:1 and for the DRV N18 is 18:1. Magnification range is the range of magnifications that are possible with the system including by changing objectives. Combined with the N25 this is 8x – 800x. with the N18 it is 9x – 727x.