I am confused I have been told as long as the the fitting is EF it will fit my EOS 400D However when I look online I get a myriad of letters behind for example Canon IS II USM, L IS III USM III, DO IS USM Tamron Di Macro, Di VC USD Sigma DG APO Macro, DG Macro, DG OS The question is will they work on my body it has a APS-C (22.2 x 14.8 mm) sensor
Each brand of lens uses their own letter designation. Canon has EF and EF-S for the DSLRs (there are other mounts for mirrorless) Sigma for example i believe is DG for full frame and DC for crop sensor. L is canon pro grade, USM is a ultrasonic quiet motor, IS is image stabilization. You will find these options as you spend more money on lenses. I don't know all the tamron and sigma designations for the same you can look them up though easily. Your APC is crop sensor, the good news is that full frame EF mount will also mount on crop, because the image circle is bigger than your sensor, it just doesn't use all of the viewable glass. SO most lenses you just mentioned will work for you as long as they are for canon DSLRs. . That is why you will read about effective crop, so EF 50mm will have a viewing angle more like an EF 70mm when on a crop body. The magnification doesn't change and get magically closer to the object, so you see some people point out that a 50 is a 50 is a 50 and go into nuance about full frame lenses on crop bodies. The reverse though ...you can't put your ef-s lenses on a full frame body though as they will hit the mirror if they could mount the image will have a dark ring around it ....since the glass was smaller and made only for you crop sensor body.
Welcome to the forum, Country Lover. I have two 400D cameras which I use as a backup for my photography class, it is a excellent camera for what it is. My most used lens is a 28 to 200mm lens, It covers the majority of my images and I carry a 75 to 300mm lens. I have other lenses but these are my main two I use. Now your 400D uses compact flash cards to save your images too. If you want or can not get these cards, there are SD to Compact Flash adapters available from Ebay. I use them all the time so my students, if they need the camera, they bring their own SD card to use in the camera. I use a 500mm lens on my Crop C sensor cameras and with the 1.6 crop I get a 800mm lens. Must try a 2x extender one day. If you have access to old film lenses , you can get adapters for your camera to use them.
