Canon makes DSLR and mirrorless cameras. If you own an APS-C DSLR such as the Rebel series or XXD series ie EOS 30D, EOS 40D & EOS 7D series. Those cameras take both EF and EF-S lenses. If you own a Full camera such as the 1D series, 5D series & 6D series. Those cameras only take EF lenses. If you own a 3rd Party lens compatibility maybe hit or miss on newer cameras. EF-M, RF & RF-S lenses are incompatible with DSLR cameras. Canon has 2 mirrorless camera lineups. The EOS M system which has been discontinued. Then the current EOS R system. Do you have a budget to spend on a new camera. Canon is slowly discontinuing DSLR cameras and moving to mirrorless cameras. Your lenses can be adapted to new mirrorless cameras. If you do move to mirrorless stick with the Canon brand adapters. Also stick with the EOS R system. The EOS M system is a dead end and has been discontinued.
- EOS: Electro Optical System (What EOS stands for)
- EF: Electronic Focus: lens mount ALL EOS DSLRs & Film SLRs use (original EOS Mount) (Red Circle Mounting Index, 12 o’clock position)
- EF-S: A separate lens Mount designed for APS-C DSLRs NOT compatible and won’t mount to any Full Frame Digital, 35mm Film SLRs or APS-H DSLRs. Note this is a DSLR Crop Sensor ONLY Mount. (White Square Mounting Index, 1 o’clock position)
- EF-M: Lens Mount for EOS-M series Mirrorless cameras. Incompatible with DSLRs or EOS Film SLRs. (White Circle Mounting Index, 11 o’clock position) (2012-2023, discontinued).
- RF: Lens Mount for EOS R series Mirrorless cameras. Incompatible with EOS DSLRs or EOS Film SLRs. (Red Oval Mounting Index, 12 o’clock position)
- RF-S: Lens is optimized for EOS R series APS-C cameras. Can be used on EOS R series Full Frame cameras but the image is cropped to the APS-C image circle. Note this is NOT a separate lens mount.
- L: Canon's professional grade lenses only available in Full Frame lenses NO APS-C lenses.
- DO: Diffractive Optics uses Fresnel lenses
- I, II, III, IV, V: Some lenses have multiple revisions such as the EF 28-80 F/3.5-5.6 V USM (ONLY lens to have a Version V)
- Ring Type USM: AF motor type. Provides fast focusing stands for Ultrasonic Motor. Ring Type USM is the original USM AF motor. Shaped like a ring inside the lens. Allows Full Time Manual Focus either Focus by Wire or mechanical.
- Micro Motor USM: Cheaper and slower AF Motor doesn't allow Full Time Manual Focus. Lens uses gears to adjust focus. EXCEPT for the EF 50mm F/1.4 USM lens (refer to Ring Type USM Mechanical Focus override). (1993-2016, replaced by Nano USM)
- Nano USM: Combines STM and USM technology for fast AF. Allows Full Time Manual Focus is Focus by wire. (2016- Present)
- STM: Stepper Motor for quiet AF. Allows Full Time Manual Focus which is Focus by Wire. (2012- Present)
- AFD: Arc-Form Drive original EOS AF motor. No longer in use was replaced by Micro Motor in 1993 for new lens designs. No Full Time Manual Focus (Retired 1987-1992)
- Micro Motor: Older least advanced AF motor slower AF used in cheaper lenses. No Full Time Manual Focus. (Retired, 1993-2012) Replaced by STM in 2012.
- IS: Image Stabilization available in the lens.
- IBIS: In Body Image Stabilization available in select EOS R Series cameras.
- Macro: A macro lens with 1:1 magnification
- Compact Macro: Lens is able to focus closer than a normal macro lens.
- MP-E: Manual Focus only electronic aperture control no focus to infinity.
- TS-E: Tilt Shift lens with electronic aperture control no Autofocus.
- Soft Focus: Lens is designed to provide a creamy bokeh effect.
- PZ: Power Zoom lens. Only 1 lens released with this feature. Only the EF 35-80mm F/4-5.6 PZ lens used this.
- TTL: Through The Lens Flash metering. Flash system relies on light reflected off the film. NOT compatible with EOS Digital cameras.
- A-TTL: Advanced Through The Lens Flash metering system in EOS film bodies released in 1986. Replaced by E-TTL in 1995. System uses a pre-flash measured by a sensor on the speedlite itself. NOT compatible with EOS Digital cameras. Uses EZ series speedlites
- E-TTL Version 1: Evaluative Through The lens Flash metering system. System uses a pre-flash measured by the camera body to calculate flash exposure. System also relies on AF point selection too. Compatible with EX or EL series speedlites. Replaced by E-TTL II in 2004.
- E-TTL II: Refer to E-TTL Version 1. System was released in 2004 and works similarly to the original E-TTL. But uses focus distance information from the lens. Via a distance encoder in the lens. E-TTL II doesn't rely on AF point selection. Note E-TTL II is IMPLEMENTED in the camera body NOT the speedlite.
- EOS M Series: A discontinued APS-C mirrorless lineup of cameras (2012-2023). Replaced by EOS R Series APS-C cameras in 2023. EF-M lenses CAN NOT BE ADAPTED to EOS R Series cameras.
- EOS R Series: Originally released in 2018 with Full Frame cameras only. Later in 2023 with APS-C cameras. New APS-C lenses were released.
