| Its never easy when they give you too many choices. You want a lense that you can use the whole diameter of the lense without getting any distortion on the edges and I'm not sure what they call that, its not color corrected. I'm not an expert on optics but I think the focal length will shorten as the power goes up, 10x will have a longer focal length than 20x. 10x should be good for anything you want to look at. Why don't you phone Rio grande and ask, if you are lucky they may be able to tell you what you want to know on the first call.
DFrey |