2x teleconverters?

[gene_can_sing]

Do any of you guys use teleconverters of any sort? I plan on getting a 7D soon, and I film surfing and can't quite afford a really expensive lens. There seem to be some reasonably price 300mm Canon EF zooms. I was thinking about attaching a 2x converter to it and making it a 600mm. For surfing, the more zoom the better.

What are the drawbacks to Teleconverters? Loss of image quality (how much)? Loss of a stop?

What would be a good one for a Canon EF lens? How much should I expect to spend?

Thanks in advance!

[morgan_moore]

Loss of two stops for a dubler

softer, should worry about vingetting on a small chip cam

you will need a F4 lens at least

S

[rallymatt]

http://cgi.ebay.com/FUJI-FUJINON-T-600mm-5-6-EBC-M42-SCREW-MOUNT-PENTAX_W0QQitemZ230384919213QQcmdZViewItemQQptZFil m_Cameras?hash=item35a402e2ad

[atomick]

I have the Canon 300mm f4 IS and a 1.4x teleconverter. On the Canon 7D, this gives you the equivalent of 672mm with the "crop factor" of its non-FF sensor. I don't find a huge reduction in image quality, although I can't shoot at less than f5.6 - f8 makes things sharpen up a lot. Make no mistake, though: This kind of extreme focal length requires really serious stabilization, so think heavy sticks and a beefy head.

[Ryan Farnes]

1) Any thoughts or experience by anyone with non-Canon teleconverters? Tamron, Kenko, etc....?

2) Seems most comments people make about teleconverters in general has to do with image quality being decreased. I've read that there is some quality lost with 1.4x and more with 2x. I wonder if the image quality is more of an issue for still photographers that are taking 10+ megapixel photographs? Will the difference between 1.4x and 2x converter be significant enough in 1080p video to consider going with the 1.4x instead of 2x to maintain more clarity? Or does the 7D not resolve detail well enough to matter? Also, a lot of photographers talk about edge detail being lost, but with the 7D being APS-C, may not be a problem?

3) Light. 1.4x loses 1 stop of light, 2x loses 2 stops. Auto-focus may not work, which seems irrelevant for video. Anything else I need to know?