Review on EF 1 4X III Teleconverter Extender by Sean Young

I like Yongnuo products and this teleconverter is no exception. It's well made and works great with both Canon 5D Mark IV and Canon 6D. I mainly use it with a Canon 300mm f/4 lens when photographing birds (mainly eagles and hawks in flight) to get a little more coverage with just an aperture loss. I am very satisfied with this product. It worked well and saved me a significant amount of money compared to buying a Canon teleconverter.