Extender or adaptor?

Hi.
Sorry for my bad english!
I have Canon EOS 50e (Elan II e) and Sigma 70-300 DL Macro Super.
I am satisfacted of this lens.
I want to photograph animal and birds and I think about to buy
extender 2x for Sigma lens.
The question is: does extender work with Sigma?
Which brand is better with my Sigma? For example: Canon, Kenko,
Tokina, Tamron, Sigma, ....
In alternative I have this scope:
http://www.telescope-service.com/spo...art.html#20x80
is preferible to buy adaptor for Canon EOS?
Thanks for suggestions!

Francesco

Felix wrote:
Hi.
Sorry for my bad english!
I have Canon EOS 50e (Elan II e) and Sigma 70-300 DL Macro Super.
I am satisfacted of this lens.
I want to photograph animal and birds and I think about to buy
extender 2x for Sigma lens.
The question is: does extender work with Sigma?
Which brand is better with my Sigma? For example: Canon, Kenko,
Tokina, Tamron, Sigma, ....
In alternative I have this scope:

http://www.telescope-service.com/spo...art.html#20x80
is preferible to buy adaptor for Canon EOS?
Thanks for suggestions!

Francesco
The 2X extender will almost certainly be better than the spotting scope
as spotting scopes usually are not corrected very well off axis. Any
of the converter brands you mention should be of acceptable quality.
The Canon converters are excellent. Check to make sure there are no
interference problems with the lens elements that protrude from the
front of the Canons into the back of your lens. I would avoid the
Canon if you can't try it out in the store. Most of the third party
converters will fit any lens but they sometimes come in two grades, say
4 or 7 elements. Get the better one if you can afford it. I have a
Tamron that I like. The better grade Kenko would be fine too. The
Sigma APO converters are NOT recommended for the 70-300DL according to
the Sigma web site.

Felix wrote:
Hi.
Sorry for my bad english!
I have Canon EOS 50e (Elan II e) and Sigma 70-300 DL Macro Super.
I am satisfacted of this lens.
I want to photograph animal and birds and I think about to buy
extender 2x for Sigma lens.
The question is: does extender work with Sigma?
Which brand is better with my Sigma? For example: Canon, Kenko,
Tokina, Tamron, Sigma, ....
In alternative I have this scope:

http://www.telescope-service.com/spo...art.html#20x80
is preferible to buy adaptor for Canon EOS?
Thanks for suggestions!

Francesco
The 2X extender will almost certainly be better than the spotting scope
as spotting scopes usually are not corrected very well off axis. Any
of the converter brands you mention should be of acceptable quality.
The Canon converters are excellent. Check to make sure there are no
interference problems with the lens elements that protrude from the
front of the Canons into the back of your lens. I would avoid the
Canon if you can't try it out in the store. Most of the third party
converters will fit any lens but they sometimes come in two grades, say
4 or 7 elements. Get the better one if you can afford it. I have a
Tamron that I like. The better grade Kenko would be fine too. The
Sigma APO converters are NOT recommended for the 70-300DL according to
the Sigma web site.

thank you