When I put a 2x AF converter on my Canon EOS 300 the autofocus hunts and wont focus clearly. Is this a common problem or is it the converter.

Jeff

-- Jeffrey Alan Herrington (jeffreyherrington@hotmail.com), April 06, 2002

Answers

Adding a converter cuts back on the amount of light entering the camera. Unless you've got a fairly fast lens to start with, this problem with AF is normal. Your camera can only AF if the lens and TC combination has an f-stop of 5.6 or faster.

So let's say your lens has a fastest aperture setting of f/5.6. Putting on a TC means that the lens is now too slow to work with AF correctly.

You can use third-party TCs or tape over Canon's extra two pin connectors and see if you can force your camera to AF with your lens, but AF will probably be unreliable anyway.

-- NK Guy (tela@tela.bc.ca), April 06, 2002.

As said, this is a normal problem. With a 2X TC, you loose 2 stops. That means that if the lens you started with is F5.6, you're dealing with an F11 lens. This is a smaller aperture than F5.6, and so AF on the EOS 300 does not work correctly.

In order to correctly use a 2X TC on an EOS 300, you need a lens of at least F2.8 or faster. It is unlikely that you will have such a lens with this camera body.

-- Isaac Sibson (isibson@hotmail.com), April 07, 2002.