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I have a Canon 70D body with Sigma 150-600 lens. I am thinking of buying Sigma's teleconverter 1.4tc but I dont know if it works in canon70D.

  • It depends on how you define "works" – Michael C Nov 29 '16 at 14:30
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Any teleconverter/extender made for the Canon EF mount will work with your camera. Your question should be, "Which teleconverter would work with my lens."

The short answer: It depends on what you consider as "working."

You'll probably think, "No." Here are the main reasons why:

  • You lose maximum aperture and thus auto focus. A 1.4X converter costs you one stop of aperture, a 2X converter costs you two stops. Because your 70D limits your auto focus system to lenses with maximum apertures of f/5.6 or wider, even a 1.4x teleconverter will disable your AF system when using your 150-600mm f/5-6.3 lens. Adding a 1.4X effectively makes your lens a 210-840mm f/7.1-10 lens. A 2X teleconverter narrows the maximum aperture another stop. Your 150-600mm f/5-6.3 becomes a 300-1200mm f/10-13 lens.
  • You lose image quality. Don't expect the image quality to be as good with the additional glass of a teleconverter between the lens and the camera. In addition to the imperfections added by the additional lens elements, the flaws in the center of your lens will be magnified by the teleconverter. Even the best and most expensive lenses combined with the best extenders will demonstrate some drop in image quality. The lower image quality of your consumer grade lens and the lower optical quality of converters that might work with that lens will give you a much greater hit in terms of image quality. You're going to give up a lot of sharpness, lose a moderate amount of contrast, and increase chromatic aberration. You may also create some irregular geometric distortion as the typical pincushion distortion of the long end a telephoto zoom interacts with the typical barrel distortion created by the teleconverter. While a good bit of the pincushion will be offset by the barrel, what remains will be difficult to correct.

For more, please see this answer and this answer.

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