Canon R7 RF vs RF-S lenses

[Woodbadger]

So, I am quite a neophyte here, so please bear with me.
I have read that the difference between RF and RF-S lenses is the size of the “circle” of light that is projected to the sensor. That is why you have to put FF R series cameras into crop mode when using them. Also that when using RF FF lenses on an APS-C body only part of the scene is projected to sensor, hence resulting in the crop.
Please clear up something for me. Does the above mean that the 35 mm focal length equivalent of an RF-S lens used on an APS-C body 1:1, or is there still the 1.6x crop factor? So, for example, would using a 16mm RF-S lens on an R7 give a different result than a 16mm RF lens?

 

[PKM-UK]

Hi Ian,

An RF-S 16mm lens on a crop sensor R7 would have an equivalent focal length of 25.6mm, the same as the RF 16mm (16 x the 1.6 crop factor).

(The equivalent 35mm - i.e FF - focal length is generally cited, but you must factor in the crop, which with Canon is 1.6x. The caveat to this is that some manufacturers cite the equivalent focal length - e.g. our Sony RX10 IV cites a 24-600mm focal length. This is ‘kind-of correct’. However it has a 2.73x crop, so the lens actually has a focal length of 8.8-220mm).

The Canon RF 100-500mm lens on the R7 has an equivalent (x1.6) focal length of 160-800mm. Often a very good thing!

(An RF-S 100-500mm lens on the R7 would also have an equivalent focal length of 160-800mm).

‘Equivalence’ is a perennial nightmare (and I hesitate to stumble into this minefield), but my understanding is this effects field of view, depth of field and diffraction, but not light falling onto the sensor, i.e f/2.8 on my FF R5 is f/2.8 on our R7 and f/2.8 on our 2.73x crop Sony RX10 IV. (Sensor differences may also blur some of the lines).

(If I‘ve strayed far from the path of truth, I suspect someone will be along to smack me in the teeth very shortly *… )

Phil

(* Hopefully equivalently).