12-26-2019 03:56 PM
Of course I'm biased, but I do want to put my 2 cents in, just for the sake of argument, please.
The new RF lenses have been designed from the ground up with an eye to the future. I saw an article that said it was designed it for the next 35 years! 😮 They have the new RF mount, which is giant at 54mm, so it can let in more light than the smaller EF lens mount, it allows the lenses to sit closer to the image sensor, so it allows the new lenses to achieve better optic quality. It also has more pins than the EF system. This allows for more data to be captured by the camera from the lens. This is where the control ring comes into play right now, but it also allows information to be transferred faster between the lens and the camera body.
THIS brochure (starting on page 6) came out with the release of the EOS R, but it has a lot of really neat technical information about the RF lens mount and design of the system. It's worth a look!
12-26-2019 04:22 PM
I have an RF 24-105mm F/4
Excellent standard zoom. I wish they would make that at f/2.8, but I guess I have to live with 24-70mm. If yo have that lens, than I would definitely want to expend my focal lengths given a choice. I still say go for a 70-200mm.
Of course, the RF mount lenses is probably the best way to go, moving forward. If your budget says EF 70-200mm f/2.8, instead of RF 70-200 f/2.8, then go for the EF mount.
I would not recommend the budget priced EF 50mm f/1.8 STM on a 30MP body. Although, it is inexpensive enough to give it a try. If it cannot resolve well enough for the sensor, return it.
12-26-2019 05:42 PM
"I have an RF 24-105mm F/4"
Then this advice is what needs to guide you.
"The industry seems like it wants to go mirrorless. But you seem to think buying old tech and adapting it to the new is the least expensive way to go."
Get the "R" model of the 70-200mm zoom. It will prove to be cheaper and the best choice in the long run. My intuition tells me the days of the "EF" mount has already been written.