Be careful about your vocabulary here... the way you phrase it is a tad confusing and perhaps incorrect. The f/stop number that we talk about when we discuss our lenses refers to the maximum aperture width or minimum f-stop number that the lens is capable of opening up to. So, a smaller number means a wider maximum opening, meaning that the lens is capable of letting more light through. For example, my 50mm f/1.8 is able to let more light thgough to the film than my 17-35mm f/2.8-4.0 (the range of f/stops on the second lens refers to the maximum apertures at different focal lengths, since it is a zoom lens). I hope this clears things up.duncanp said:the F value is the minimum aperture you can set when using the lens, i would also reccommend a long telephoto like 80-200mm or 90-300mm