Aperture...f/5.6 Focal Length...100-300mm This is a fairly old product. There are three spots of internal dirt visible. It was attached to a camera that is no longer usable, so I haven't been able to confirm its operation. However, it was working properly during the time it was attached to the camera. I will sell it to someone who understands that it is a used item. I am an amateur, so I cannot answer specialized questions. Thank you.