Hi James F.: I'm reasonably certain as long as your Canon Rebel T3 will take an EF lens (red dot as opposed to the white square if it has both it will take both EF and EF-S) you will have no problems of any kind. Here is a website that covers just about every Canon lens out there as to quality and usage, it also covers lens compatibility. http://photonotes.org/articles/beginner-faq/lenses.html. Under the UHH FAQ Sensor Sizes Chart Nikonian72 has posted an excellent example of the difference between a full frame 35mm and various cropped sensor cameras, it has not only an easy to understand coverage chart but also a photo showing what you actually see and take with both the full frame vs cropped frame cameras. Note the image sizes are exactly the same with both sensors, the difference is how much more area around the subject is included with a full frame sensor. At the very top of the forum page, you see Ugly Hedgehog - Photography Forum Just below that there is a list of tabs the third one is search, click on that and type in FAQ: Sensor Sizes Chart hit enter the information and the chart should come right up. You might also use the help tab, last in the first row of tabs. to gain the same FAQ information. Hope this helps.