This 20mm PL extension tube dramatically shifts the lens's focus scale toward near focus, allowing the lens to focus at extreme and macro distances but at the cost of losing the ability to focus deep and less than one stop of light. This macro tube is fantastic for macro and extreme close-up inserts, but note it is not capable to allow a rack focus from far focus to macro range, as a true macro lens can do. Additionally, the Duclos PL extension tube is a great alternative to diopters, depending on your needs. This 20mm PL extension tube works mainly with 50mm lenses and longer. For wider focal lengths please see my listing for the 15mm PL extension tube.