Hi and welcome to the forum:
If you have a Canon Rebel camera, then it is very possible that you actually have two kinds of lenses:
EF lenses are designed for full-frame cameras and work perfectly well on crop sensor bodies like a rebel
EF-S lenses are specifically designed for crop-sensor (e.g. Rebel) bodies, and are not designed to work fully with full frame sensors. In the DSLR world, this meant that they would not even physically fit into a full-frame body, but one can physically mount them on a FF R-series body, but there are limitations.
The R8 will sense that you have installed an EF-S lens and will automatically reduce the area of recording within the sensor to that of an APS-C camera because the lens projects a narrower cone of light back towards the sensor and will not fill it with an image, creating a huge vignette. This is significant, as it reduces the MP count of the camera down by a factor of 2.56, so the full 24MP FF sensor of the R8 will render only about 9.7MP with an EF-S or RF-S lens.
Furthermore, while there are many more modern EF-S lenses out there, a lot of kit lenses, especially older ones, will not perform well on a high-quality FF sensor on the R8.
No matter what lens you have (EF or EF-S) you will require an EF-RF adapter to physically connect those lenses to an R-series body.
So, to get the most from an R8, I would suggest you strongly consider a native RF (not RF-S) lens. You also get an optic designed to make the best use of the new sensors and other features of the R-series bodies.
cheers, TREVOR
The mark of good photographer is less what they hold in their hand, it's more what they hold in their head;
"All the variety, all the charm, all the beauty of life is made up of light and shadow", Leo Tolstoy;
"Skill in photography is acquired by practice and not by purchase" Percy W. Harris
