This lens is capable of focusing directly to a 1:2 reproduction ratio, and down to 1:1 using the Extension Tube FD50U. Many photographers perfer this focal length for photomacrography, since it gives them twice the working distance as a 50mm lens for the same reproduction ratio. This allows more room for lighting equipment and more distance from sensitive subjects. This lens incorporates into the helical focusing mechanism, a special friction damping device, to prevent unwanted focus changes when used in vertical applications. SPECIFICATIONS Type: telephoto/macro Construction: 5 elements in 3 groups Angle of view: 24 degrees Minimum Aperture: F/32 Closest Focusing Distance: 1ft 6in w/FD50-U Filter size: 52 Lenshood: optional BT-52 Length: 3 3/4 in Weight: 17oz.