I use to years ago. Ive got to where I can jugde distance pretty well. I also use my sights to calculate distance. You can use the distance between your last pin and first pin to estimate the distance due to the size of the deer as it appears between the two pins. With a little practice it is pretty easy to do. I also practice all over my yard with out ranging the distance. I put up my 3 d and practice judging distance and making shots. Like I said, with a little practice it is easy to do.