I need some help! I want to buy a converter for my Canon 350d, i now Canon has a AF Apo tele converter 2* but does it work for my Sigma 170-500mm Apo DG & 150mm Apo macro DG ?
In general you will want to get a converter that matches your lens. Since your lenses are both Sigma, I would consider getting the matching Sigma converter.
2x converters in general will visibly degrade images. 1.4x converters will usualy give you much better image quality.
As far as AF, I believe the 350D can autofocus with a maximum aperture of f/5.6 or faster. Since the largest aperture on the 170-500 is f/5-6.3 my guess is it will not autofocus on your camera with any converter.
Guy, when you say that a 1.4x converter will usually give much better image quality, do you mean that the quality degradation that results from the use of the converter is offset by the fact that you don't need to crop the frame as much? I have the Canon 1.4x converter which I occasionally use (though I lose AF functionality on my 100-400 L lens). Thanks.
Jason, yes - that's a more accurate representation. A good 1.4x converter will still have sufficient resolution to provide more detail than a cropped image without it.
Thanks for the clarification Guy. Although I rarely use the converter due to the loss of AF, I should probably work on my manual focusing skills and it might come in handy when shooting large, relatively stationary subjects like elk. I just moved from the 30D to the 5D and I miss that 1.6 crop factor!
Discussion
5 replies2x converters in general will visibly degrade images. 1.4x converters will usualy give you much better image quality.
As far as AF, I believe the 350D can autofocus with a maximum aperture of f/5.6 or faster. Since the largest aperture on the 170-500 is f/5-6.3 my guess is it will not autofocus on your camera with any converter.
Guy
Jason
Guy
Kees