Canon EOS 20D teleconverters

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M P - 31 Jan 2005 04:47 GMT

Hi All!

It's great to find a group like this! After using a Canon EOS Rebel film
camera for years, I just upgraded to the EOS 20D. I would like to know what
your opinions are on the various teleconverters? I am wanting to get a 2x
converter. I've used a Tamron 1.4x on my film camera 75-300 lens with
excellent results for years. However, Canon says that their 1.4x and 2x
converters only work with full autofocus on a few lenses, with f/2.8 or
larger. Phoenix and Kenco both make 2x converters that apparantly work on
any lens f/4.0 of larger. Any ideas, help, recommendations would be greatly
appreciated! Also, cam someone please explain what the number of groups and
elements mean and which is "better"? Thanks very much!

Marc
glaucus@earthlink.net

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Randall Ainsworth - 31 Jan 2005 05:31 GMT

> It's great to find a group like this! After using a Canon EOS Rebel film
> camera for years, I just upgraded to the EOS 20D. I would like to know what
[quoted text clipped - 6 lines]
> appreciated! Also, cam someone please explain what the number of groups and
> elements mean and which is "better"? Thanks very much!

When it comes to teleconverters, there is no such thing as "better".

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Alex - 31 Jan 2005 12:57 GMT

>camera for years, I just upgraded to the EOS 20D. I would like to know what
>your opinions are on the various teleconverters? I am wanting to get a 2x
>converter.

Just note that any magnification more than 1.4 will earn you much
lower quality shots (e.g. lower resolution, distortion, fringing).

> I've used a Tamron 1.4x on my film camera 75-300 lens with
>excellent results for years. However, Canon says that their 1.4x and 2x
>converters only work with full autofocus on a few lenses, with f/2.8 or
>larger. Phoenix and Kenco both make 2x converters that apparantly work on
>any lens f/4.0 of larger.

That's because those TCs don't report the aperture to the camera. If
you do buy one of those TCs and use it on a f4.0 camera, expect lots
of hunting (for focus) - and not all of the hunting will result in
success.

> Also, cam someone please explain what the number of groups and
>elements mean and which is "better"?

AFAIK, the less elements, the better. But, really, that's something
that I wouldn't worry about as much as the quality of the glass. The
50 1.8 has only 6 elements and, although a good value, its quality
doesn't compare to the 70-200 2.8L IS which has 23 elements.

Read the reviews over at http://www.fredmiranda.com/reviews/ to see
what photographers think of the stuff you want to buy. And, if you're
asking for advice on *what* you should buy, please tell us what you
want from the lens and what you expect to shoot with it.

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Alex
atheist #2007

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