That isn't a great option for a telconverter. And the lens isn't really designed for a t/c anyway. There are some options you could do. I would never, ever do a 3x T/C. It just degrades the quality far too much. I usually settle on a 1.4x, and sometimes a 2x. If you want to use your Sigma lens, you can, but it will never be stellar. I would look at the Kenko 1.4x or 2x teleconverter. It is quite good. Sony and Minolta AF t/c's won't work because of..... Sony's choices on the LA-EA4/3 design. It is frustrating.
Myself, I use a manual focus Minolta MD 300/4.5 and the matched 300-L (long, versus the S, which is short) for an effective focal length of 600mm and f/9. Another quite good teleconverter is the Vivitar 1:1 Macro 2x teleconverter. It adds in the bonus of shortening your minimum focus distance so you can use a lens for close up/ near macro photography. I use it with a Minolta MC Rokkor PG 50/1.4, to give me a 100/2.8. I figure it actually gives me a 1:2 magnification.
Another option is the Minolta 500/8 mirror lens. It is much better than most any other mirror lens given its increased diameter giving a true f8 (some are closer to f11 in light gathering) and it has AF. It runs about $325. There is also a manual focus Rokkor version which is a couple of hundred.
jova castle wrote:
mcbroomf wrote
jova castle wrote
https://www.flickr.com/photos/139844455@N07/24663512045/in/dateposted-public/
Anyone please advise me why am not getting a sharp image..? This is on Sony A7 300mm+2+2+3X teleconverter Looks reasonable to me. What were your expectations?
Also;
Diffraction (what was your F stop?)
Lens quality (what lens and converters did you use)
ISO (what ISO?)
Crop (how much is this cropped?) Thank you for the response.
F12, Vivitar converter Sigma lens, ISO 400, uncropped.
Otherwise without the Vivitar adapter Sigma 70-300 is sharp on my Sony A7