see also:

• Sony FE E-mount full frame lenses
• teleconverters explained

• Sony has released the usual 1.4x and 2x teleconverters but these are only compatible with certain GM lenses although apparently can be used on certain other lenses but you may lose AF capability (eg. Sony 70-400mm F/4-5.6, Sony 135mm F/2.8)

• 6 elements on 5 groups
• 33.6mm long
• 167g
• compatible lenses:
  • Sony FE 70-200mm f/2.8 GM OSS
  • Sony FE 100-400mm f/4.5-5.6 GM OSS
  • Sony FE 400mm f/2.8 GM OSS
• $AU899 / $US548

• 8 elements on 5 groups
• 42.7mm long
• 207g
• compatible lenses:
  • Sony FE 70-200mm f/2.8 GM OSS
  • Sony FE 100-400mm f/4.5-5.6 GM OSS
  • Sony FE 400mm f/2.8 GM OSS
• $AU899 / $US548

• http://kurtmunger.com/sony_teleconvertersid229.html