Can you use RF extender with EF Adapter?

You can use an RF extender with an EF adapter, but you will need to use a modified adapter. The Canon-made EF-EOS R adapter is not compatible with RF extenders. However, there are a few third-party adapters that have been modified to work with RF extenders.

Here are a few of the modified adapters that are compatible with RF extenders:

• Commlite EF-RF adapter
• Viltrox EF-RF adapter
• K&F Concept EF-RF adapter

When using an RF extender with an EF adapter, you will need to keep in mind the following:

• The maximum aperture of the lens will be reduced by the amount of the extender. For example, if you use a 2x extender with a lens that has an f/2.8 maximum aperture, the maximum aperture will be reduced to f/5.6.
• The image quality may be slightly degraded, especially at the edges of the frame.
• The autofocus performance may be slower, especially with telephoto lenses.

If you are considering using an RF extender with an EF adapter, I recommend doing some research to see if the benefits outweigh the drawbacks for your particular needs.

I hope this helps!