EF to R Lens adapters

[craigM24]

Do the adapters for using EF series lenses on the new R series camera change the focusing focal length?  I mean do they function like extension tubes?

[deebatman316]

No the adapter makes the lens sit at the correct distance from the image sensor. Just as if you were using it on a DSLR.

[rs-eos]

The focal lengths would not change.

The only current Canon EF to RF adapter that will alter some aspects  would be the special 0.71x adapter for use with the EOS C70.   That will focus the entire area of the EF lens onto the smaller Super 35 sensor of the C70.  Thus, for light gathering purposes, it will give you an extra stop.   And, it will give you a field of view very close to what that lens would give you with a full frame sensor.

Example:  When I use that adapter with my EF 50mm f/1.2L, the focal length is still 50mm.  The field of view is still that (very close) of a 50mm lens (instead of the 80mm field of view if using an RF 50mm with the C70).   Light gathering is that of an f/0.9 lens.   I don't think the depth-of-field values change though I have not confirmed that.