2x teleconverter with autofocus for Sigma 50-500mm lens?

crawshs · May 2, 2007

Hi, Does anyone know of a 2x teleconverter that I can use with my Sigma 50-500mm f/4-6.3 EX DG HSM lens which will support auto-focus? Am I expecting the impossible?

Cheers,

Simon

fmw · May 2, 2007

I hope you aren't expecting excellent image quality. In my experience the 1.4X or 1.5X converters are a bunch better. You can crop the images to the angle of view of a 2X and still do better than you would with a 2X. Get a heavy tripod.

lostprophet · May 2, 2007

AF isn't possible with a 2x converter with that lens and from memory not even with a 1.4x

Big Mike · May 2, 2007

Welcome to the forum.

Typically...most cameras need the light equivalent of F5.6 for autofocus to work. A 2x teleconvertor will steal about two stops of light....so if you look at your lens, with a max aperture of F3.5-4.5...then subtract two stops, you will have less light than F5.6...so auto focus probably won't work. You could still manually focus...but going back to what Fred said...it's probably best to forget about the 2X converter anyway...it will just hurt your image quality too much.

crawshs · May 2, 2007

hey guys, thanks for the advice. know i'm pushing things quite a bit with that setup. i'll try playing with a 1.4x as you suggest.

forzaF1 · May 2, 2007

I have a Nikon 2x teleconverter and it has been nothing less than great, but I use it with my 70-200mm f/2.8 VR, so I still have decent aperture. With that 50-500mm lens, you will not have very much light to work with, due to the teleconverter taking 2 whole stops away from you. The 2x teleconverter will only work really well on a lens with a sub f/2.8 level for the most part. With this said, the 1.4x and 1.7x teleconverters are also nice pieces of glass.

JDP · May 2, 2007

And hey, if you have $8,000 you can always pick up an AF-S Nikkor 400mm f/2.8D IF-ED II That'll use a 2x teleconverter and still allow AF.

And when you're done with it, I'll take it off your hands - how's $1,500 sound?