You Can't Get Any Shallower!
I spent most of my time shooting in Texas using the TC-20e3 and I couldn’t have been more pleased with the results. And while it provided a bigger subject in the frame, the trade off was basically NO DOF! What do I mean?
You’ll see a line in the photo, that’s the focus plane. I focused in the middle of the back on the dragonfly. I was at f8 (f4 w/2x) but has an effective f/stop of 6.7 and was shooting 17′ away from the critter. If you look at the photo, you see most of the stick is sharp since it was in the focus plane. If you look just a 1/2″ in front of the focus point and 3/4″ of an inch behind it on the wings, you’ll see the focus is gonzo! That’s just how narrow the DOF is with the 600VR / TC-20e3 at 17′.
Now this can be a good thing or a bad thing. If you want a lot of DOF, this is a bad thing. If you want the background to just disappear, it’s a good thing. Can you work around the narrow DOF? In a way you can things happen. If you have the subject on the same plane as the plane of focus, then the entire subject will be sharp. As like this butterfly, it is flat to the plane of focus so its wings are all in focus. But anything in front of or behind those wings are gone. You as the photographer have to decide first what’s the subject then where to focus the lens and lastly how much will be in focus with DOF. There are plenty of tools to go either way, use them all to your advantage!