I have been making hunting videos for around 30 years. I am new to the DSLR camera world. I bought a Canon Ti5 and am window shopping for a lens. I think I know what I want to get as far as a lens goes,an 18-135 mm lens. What I don't understand are any of the abbreviations at the end of the description of the lens, like stm, usm,and there are more. I saw a few that just said "Standard". I just want to get the right lens the first time around without having to send it back. I will be using this lens for tree stand hunting. If some one could take a couple minutes to tell me what these abbreviations are I would appreciate it. Thanks! Steve
USM is Canon's naming system for one of their autofocus motor systems. It stands for ultrasonic motor. STM motor systems are stepper driven. USM tends to be a bit faster to focus, but will still produce sound that is audible during video. STM is better suited for video as it's practically silent (albeit a bit slower). If you're shooting a lot of video and utilizing your camera's AF (which you should since your camera has great video AF), then lean toward STM versions. Sent from my Turbo 2.
