On the surface, teleconverters seem like a fantastic way to help a lens pull double duty by allowing you to extend its focal length for a lot less than it would cost to buy another entire lens. While they can be quite useful, they also have some drawbacks you should be aware of before you buy one. This helpful video will show you their pros and cons as well as some other options to help you decide the best approach for your work.
Coming to you from David Bergman with Adorama TV, this great video will show you the pros and cons of using a teleconverter to get more reach from lenses you already own. Teleconverters generally come in two flavors, 1.4x and 2x, named for the factor by which they increase the focal length. The main drawback is one of physics, as the 1.4x teleconverter reduces a lens' maximum aperture by one stop and a 2x teleconverter reduces it by two stops. However, you also may encounter issues like reduced image sharpness and slower autofocus speeds. That being said, modern teleconverters (particularly 1.4x options) are quite good and will generally be more than satisfactory for most applications. Check out the video above for the full rundown from Bergman.
I added the 2x TC to my 800mm RF lens and Canon RP. I have no regrets.
Using a teleconverter successfully depends a lot on the image quality of your primary lens you are mounting it on. Second is the usage. In my personal application I use a 1.4X on my RF 100-500 zoom. I use this combination for song birds: small target at close distance. The goal is to fill the frame with your subject, not to have to crop afterwards. There is a drop in image quality with this setup but in my experience it is totally acceptable. If the subject is still too small with this setup it is because the subject is too far and I must close the gap physically. A longer lens or a 2X extender is usually not the answer because of atmospheric distortions and/or unacceptable image quality in the weather conditions I usually shoot.
When I know I will not be shooting a target more then 30ft away, I'll toss some extension tubes (with auto focus) on my 200-500 lens to get a little extra reach without sacrificing any quality (no glass). Great for small birds that favor a small area or bush.
One downside of extension tubes is you can't focus to infinity, the more you add the closer objects have to be.
Correct. I mentioned that in an indirect manor.
Though I should have used the word "magnification" instead of "reach", doh! The up-side is that I rarely find myself shooting at infinity at 500mm. Most of the time 50ft and under; so no worries loosing that infinity focus. 🙂 At least for where I shoot, everyone's needs differ of course.