mounted on a teleconverter. The lens also reduces autofocus speed when a teleconverter is attached to improve autofocus accuracy. List of Canon EF lenses The "I", "II", "III" Roman numeral suffix after the focal length(s) indicates the generation number. While I is used in the table below, it is not used in official Canon model numbers; the original model lacks a Roman numeral and only the second and subsequent generations have them. Roman numerals are used only when the entire model designation—focal length(s), aperture, IS, DO, L status, and motor mechanism—is identical from one version to the next. This means, for example, that when Canon introduced IS to lenses whose prior versions lacked that feature (24mm, 28mm, 35mm IS primes in 2012, 16–35mm IS zoom in 2014), the first IS versions lacked Roman numerals. The EF lenses are grouped below by their focal lengths: Zoom: for zoom lenses that have a range of focal lengths Prime: for prime lenses that have a single focal length Zoom Prime Exceptions Canon has two further types of lenses compatible with the EF mount: Tilt-shift and the 1-5x Macro lens, which are not designated EF, but TS-E and MP-E respectively. TS stands for Tilt-shift while MP stands for macro-photo. These types of lenses are not designated EF as they are manual-focus only lenses. They do, however, retain electronic aperture control as well as focus confirmation. Special See also Canon FD lens mount Canon EF-S lens mount Canon EF-M lens mount Canon RF lens mount Notes References Markerink, Willem-Jan. Camera Mounts & Registers. Retrieved on 6 November 2005. tiffen.com. Lens To Filter Chart. For list of filter sizes. External links EF Lenses at the Canon Camera Museum List of all Canon SLR lenses with technical specifications Lens mounts