Summary: I have owned the Sony 300mm f/2.8 G lens for a long time. I also had the Sony 2X TC but had mixed feelings about the results I was getting. The 2X caused loss of contrast and in low light my A900 would have difficulty finding auto-focus. After years of second guessing myself I finally bought the 1.4X TC. I wish I had bought it sooner. Other than the expected loss of one f-stop, there is no downside!
No downside other than the expected loss of 1 f-stop.
David De Bar, Amazon
20 February 2014
Summary: I use this TC on my Sony 300mm f/2.8 lens mounted on an A900 camera. I bought the 300mm lens at a good price from a photographer who needed to raise money quickly. I bought her Sony 2X teleconverter at the same time. I loved the 300m lens but was consistently disappointed when I used the 2X TC. The softness and loss of contrast of 2X all but negated the advantage of the magnification. I found I could do almost as well or some times better by cropping.
Excerpt: I use the Sony 1.4x with Minolta 200mm 2.8 HS APO G and A900. I don't see optical quality degrade much, only a little lower contrast at wide open, but it is still fully useable. Stop down a little to f/4.5 regain most the contrast back. The pictures look about the same compare to Sigma 100-300mm 4. Only the Tokina 300mm 2.8 stop down to f/4 looks a little bit sharper than the Minolta+Sony 1.4x TC.
Pros: Consistent Output, Easily Interchangeable, Fast / accurate auto-focus, Lightweight, Strong Construction
Summary: I bought this 1.4 teleconverter because I cannot afford the 12,000 dollar 500mm telephoto lens. I thought I'd try this on my 70/400 mm telephoto lens. Problem is I cant manually focus the long shots, which is why I bought this. So I have this expensive piece of gear for moon shots. For now. All the Canon and Nikon guys have them, not sure why they have them, but I'll ask next time I go out. It looks good on my camera!
Excerpt: I am a wildlife photographer. First use at Merrit Island and Vera Wetlands. Works great with 70-200 f/2.8; fast AF. With 70-400G lens no auto focus. It takes practice but works great. With focus peaking, can focus quickly in majority of situations. Use the a77; shoot in RAW and see no noticible difference in output with it on/off. Worth the price. Glad I purchased it.
Pros: Easily Interchangeable, Fast / accurate auto-focus, Strong Construction, Use 70-400 No Af
Summary: This very expensive Teleconverter is not compatible with the 300G 4.56 Telephoto Lens, It will not even connect and allow you to work in Manual Mode. It will connect to the G 400mm lens in Manual mode. I am sending mine back to Amazon. Very disappointed.
The Sony 1.4X teleconverter does not work with the G70400 lens.
Aubrey R. Cruse III, Amazon
26 October 2011
Summary: Much to my surprise, the Sony 1.4x teleconverter does not auto-focus with the Sony G series 70-400 mm zoom. True enough, it says that the Sony 1.4x teleconverter was designed specfically for use with the Sony 2.8 lenses; however, it does not say that it will not allow your Alpha a900 DSLR to autofocus with another G series lens and the T/C.