cannon Extender EF 1.4x II and a sigma lens

photoj

I have a sigma 70-300 f4-5.6 apo dg lens. I have been considering placing an extender on it but when I researched the sigma site they don't have one for it. Would a Cannon Extender EF 1.4x II work with it? Anyone know?

ziggy53

photoj wrote:

I have a sigma 70-300 f4-5.6 apo dg lens. I have been considering placing an extender on it but when I researched the sigma site they don't have one for it. Would a Cannon Extender EF 1.4x II work with it? Anyone know?

Adding an accessory lens element to any lens, teleconverter or close focus lenses for example, you need to be concerned with two forms of coupling:

1) Mechanical coupling
2) Optical coupling

The first is whether the attachent will physically mount on the host lens, and the second is how the attachment lens affects the optical properties of the host lens.

I suspect that the Sigma 1.4x APO teleconverter wil physically attach just fine to that lens. I also suspect that autofocus and edge definition will suffer, especially at large apertures and shorter focal lengths.

The Canon EF 1.4X II is probably going to be even more problematic, since it is designed for a very few lenses to begin with and part of the front of the Canon teleconverter even extends into the host lens so that I'm not sure about physical coupling.

My own opinion is that the Sigma converter, or even the Tamron 1.4 converters, will be OK for the 100-200mm region on the lens, but then the problems that lens has at 300mm will be exagerated and render a pretty soft image, kind of defeating the purpose. You might be able to stop down and get fair quality, but I doubt you will get results like you probably want.

The Sigma 1.4x and Tamron 1.4x (probably not the SP) are fairly inexpensive, so I suggest you give them a try.

photoj

Thanks
Zuggy,,,thanks for the info. I was suspected that the problem was more on the side of focus than mechanical. Which just means I save up and get a 400 or 500 lense.