Getting a Sigma 2x Converter for Sig 70-200. Focal length?

[devilla101]

Hey guys
I'm planning to purchase the above TC for my Sigma 70-200 for Zoo shots. I have a Canon 10D and if attached to the lens will the true focal length at the long end be 640mm (200 x 1.6 x 2)?

Also is the 2x overkill or will the 1.4x suffice? I'm just worried about the image quality and the camera shake even though I'll be using a monopod.

[sirhc55]

I use this combination, normally on shutter priority with a least 1/1000th sec and it works very well

[hart]

If you're talking about the Sigma APO 70-200mm F2.8 EX DG/HSM then you're going to double the maximum aperture out to 5.6 which isn't too bad - as for the crop factor, don't consider that an increase in "true focal length", although it will "look like it".

There's often a difference of opinion about crop factor and whether or not it represents an increase in focal length or decrease in resolution, or increase in pixel size, or if it is a cause of acne.

Personally? I'd consider myself equipped with a 140-400mm f/5.6 lens and take the crop factor into consideration as far as "what you'll see in the viewfinder" is concerned (like you do already with any other lens).

If you're talking about any other lens (with a larger maximum aperture) then you're going to start having problems with auto focus not wanting to work properly.

Cheers

Leigh

[moz]

I use a Sigma 2x TC on my Canon version of this lens. It works well, but I'm thinking to getting the Canon 2x so that I can stack the TCs (I have a Canon 1.4x). But since Poon only wants $280 for a new one, I'm not sure that it's worth upgrading... the Canon is much more expensive and on a crop camera the difference is negligable.

[devilla101]

Thanks for the reply folks. What kind of image quality can I expect with a 1.4x and a 2x?

[moz]

Image quality... terrible. You're starting from ok-ish with the Sigma 70-200, and you're dropping it further with the teleconverter(s)

With my lens I find it fairly hard to tell the difference. There's a slight loss of contrast, and tests I've seen show loss of sharpness as well. Allegedly the Sigma 2x is slightly sharper in the centre of the frame than the Canon, so I bought that. But now I'm looking at going full frame it seems better to get the canon and lose the slight colour cast and loss of edge detail.