jerryc41 wrote:
The more light you want to push through glass, the more difficult it is. The smaller the maximum aperture, the less expensive the lens will be - also smaller and lighter. It takes a lot of technology and top quality glass to get another stop of light through a lens, and that costs money. Ironically, a lens with a larger aperture is not necessarily going to produce better results at that aperture.
Jerry they are both 1.2. Ef vs Rf two differing mounting systems. Like Paul has pointed out a very high grade lens but bothe being L glass.
J. R.