70-300L with extenders on R series body?

[dickgrafixstop]

Canon states that the 70-300L in not compatible with either the 1.4 or 2.0 lens extender. I understand this is because the back portion of the internals extends too far into the body that it causes contact with the mirror. Since the R series have no internal mirror, does that mean the the 70-300L could be used with either of the extenders along with the ef-rf adapter?

 

[neuroanatomist]

Canon states that the 70-300L in not compatible with either the 1.4 or 2.0 lens extender. I understand this is because the back portion of the internals extends too far into the body that it causes contact with the mirror. Since the R series have no internal mirror, does that mean the the 70-300L could be used with either of the extenders along with the ef-rf adapter?

Your description of the problem is not correct. The mirror inside the body, or lack there of, is irrelevant in this case.

The extenders have a protruding front element, and with 70-300L, the rear element of the lens is placed far enough back that the protruding front of the extender interferes with it. At least, at the short end of the zoom range. Technically, the EF extenders can be used with the EF 70-300L at the long end of the zoom range. It’s not officially supported by Canon although the reality is the RF 100-500 functions in exactly the same way with the RF extenders, and that is officially supported by Canon.

The RF extenders have the same protruding front element, and that does not allow you to use the extenders behind the EF-RF adapter (the opening in the adapter is too narrow to permit the extender to fit inside).

If you want to use an extender with 70-300L on an R body, you have two options. 1) use an EF extender in front of the adapter, with the caveat that you can only use the long end of the zoom range. 2) physically modify an EF-RF adapter to enable using an RF extender behind the adapter with the EF lens mounted in front of the adapter. I would not do number two on the Canon adapter, instead use the Commlite Adapter which has the largest hole of any of them to start with, and is cheaper than the Canon one in case you screw up the mod.

When I did it, I used a Dremel to increase the size of the opening and it worked just fine.

RF and EF extenders on the EF 600/4L IS II

After getting both the RF extenders to use with my RF 100-500L, I became curious about whether they would perform better than my EF MkIII extenders when used with my EF 600/4L IS II on my EOS R3. As most will know, the protruding elements of the RF extenders do not fit into the Canon EF-RF mount...

www.canonrumors.com