Canon RF 100-400mm f/5.6-8 IS USM

If you’re in need of a versatile telephoto zoom lens, there aren’t many choices for the RF mount. Unless you use the EF-RF adapter, there are only two options available, the RF 100-500mm or the RF 100-400mm. Is the much cheaper RF 100-400mm a wise choice? Have you made the switch to the Canon DSLR to the Canon mirrorless system? In that case, you probably have a selection of EF lenses available, perhaps lenses made by other manufacturers like Sigma or Tamron. It is no problem using these lenses with the EF-RF adapter on Canon mirrorless cameras.