Sony FE SEL20TC

The Sony SEL20TC doubles your focal length and costs two stops of light. Build quality is excellent, but optical performance drops to the bottom third of our database. Worth it if you own the 70-200mm f/2.8 GM and need 400mm on a budget.

The build quality is a standout. It sits in the 89th percentile for construction, and it feels like it. The stabilization is solid too, around the 72nd percentile, which helps when you're shooting at effectively double the focal length. But the optical score is the weak link here. It lands in the 36th percentile, which means you're giving up sharpness and contrast compared to shooting without it. The aperture score is middle of the pack at the 69th percentile, which makes sense since you're losing two stops. Autofocus is about average at the 54th percentile. It works, but it's not going to feel as snappy as the bare lens.

Comparing a teleconverter to zoom lenses like the Sigma 18-50mm f/2.8 or Tamron 17-70mm f/2.8 is a bit apples to oranges. Those are general purpose zooms. This is a specialty tool for one job: more reach. The Viltrox 35mm f/1.7 and Nikon 17-28mm f/2.8 are also completely different beasts. The real comparison is against Sony's own 1.4x teleconverter, which costs less and loses only one stop of light. If you can live with 1.4x magnification, that's the smarter buy for most people. The 2.0x is for when you absolutely need the longest reach possible and can't afford a super telephoto.

This thing isn't cheap. US listings run from $540 to $598, and Newegg has the best deal at the lower end. For that money, you could almost buy a decent prime lens. But if you already own the 70-200mm f/2.8 GM, this is the cheapest way to get 400mm of reach. A dedicated 400mm lens would cost you thousands. So in that context, it makes sense. Just know you're paying for convenience, not optical perfection.

The Sony SEL20TC is a 2.0x teleconverter for E-mount full-frame bodies. It doubles your focal length and costs you two stops of light. That's the deal, plain and simple. It's built for the FE 70-200mm f/2.8 GM OSS, and it keeps autofocus, metering, and stabilization working. Weather sealing is a nice touch for outdoor shooters.

It's small and light at 209g. You barely notice it in the bag. But it's not a magic trick. You lose light, and optical quality takes a hit. Our database puts its optical score in the bottom third. That's the trade-off for reach.

Skip this if you don't own the Sony FE 70-200mm f/2.8 GM. It's not a universal teleconverter. Also skip it if you're a pixel peeper who hates soft corners, because the optical quality drop is real. If you only need a little more reach, get the 1.4x teleconverter instead. You'll lose less light and keep better image quality.

Buy this if you already own the Sony FE 70-200mm f/2.8 GM and regularly shoot wildlife or sports where you need more reach. It's well built, weather sealed, and gets the job done. But if you're picky about image quality, the optical hit will bug you. And if you don't own that specific lens, this is useless to you. It's a niche product for a niche need.