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Can my EOS 1200d autofocus with1.4x canon teleconverter and canon 300 mm f4 lens. What will be my maximum aperture using both of these.

marked as duplicate by mattdm, inkista, Michael C, John Cavan Dec 28 '15 at 15:32

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    Did you read the specifications of the 1.4x canon teleconverter? What do they say? What exactly in those specifications is missing in order to answer your question? – Dragos Dec 26 '15 at 11:49
  • Welcome to the site. Please use our search functionality before asking new questions. Also, it is highly advised to use your manual for basic questions. – dpollitt Dec 26 '15 at 16:39
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According to Canon's website, the 1.4x Extender III is compatible with EF 300mm f/4L IS USM and

*When Extender EF 1.4x III is attached, the lens maximum aperture will be reduced by 1 stop. Refer to the camera and lens instruction booklets to see if there are any AF compatibility limitations due to the reduced max aperture.

Autofocus will also work given that you have enough light for the camera to be able to focus and you are using the largest aperture possible.

As far as I can see, the camera limits the autofocus to a 5.6 aperture

You will also get a lot more information from this answer: https://photo.stackexchange.com/a/16400/26160

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