Both Oriental Motor web site and Gecko Drives web sites have good explanations of stepper motor basics, including explanations of drive techniques.
See here for an explanation of microstepping and resolution: [www.micromo.com]
On a different site I read that motor steps are not exactly 1.8 degrees- they vary typically 5%. When the microsteps get smaller than the 5% variation in step position, the resolution can't improve because you're "down in the noise". 1/16 is >5% but 1/32 <5%.
See here for an explanation of microstepping and resolution: [www.micromo.com]
On a different site I read that motor steps are not exactly 1.8 degrees- they vary typically 5%. When the microsteps get smaller than the 5% variation in step position, the resolution can't improve because you're "down in the noise". 1/16 is >5% but 1/32 <5%.