Good move if you like to degrade the quality of the image...

I didn't know that Canon made an EF-S version of the EF 70-300 DO IS USM
lens.

To give you a useful answer, the Canon teleconverters won't work because
they have a protruding front element that will interfere with your lens.
Generally only the lenses on Canon's list should be used with their
teleconverters.  Sigma's teleconverters are similar and have the same
problem.

I have the new Canon EF 70-300mm IS F4-5.6 (not the DO version) and I
sometimes use a teleconverter with it.  It is the inexpensive Quantaray 2x
AF teleconverter.

http://www.ritzcamera.com/product/261660252.htm

When using the teleconverter, at the short end autofocus confirmation works,
but autofocus itself is unreliable since you are at F/8.  At the long end,
you are on your own with the manual focus since you are at F/11.  The camera
doesn't know you have a teleconverter on so it doesn't show up in the EXIF
data.  You have to manually remember that your real F-stop is two stops
higher (or doubled) also.  The image stabilization (IS) works fine with this
TC however and is very helpful.

Maybe I just have a lucky copy of this TC, but I can get very good results
with it.  The picture isn't quite as good as without it but almost always
better than the results of cropping and upsizing. I have even tried it with
my 50mm F1.8 (works as a 100mm F3.5 with the TC) which works well with full
AF. You cannot mount EF-S lenses however on this TC, only EF lenses.  The
rear element of the EF-S lenses sticks out too far and prevents the lens
from attaching to the TC.

With manual focus, you are relying on your eyes seeing the image on the
focussing screen sharply.  I had to order an eyepiece diopter lens from
canon since the built in adjustment didn't have quite enough range.  Since
then I can manual focus pretty well.  With the TC, the viewfinder is dimmer
by 2 stops though, so it is harder to focus.  Really it is best when you
have very high light levels.

The picture does degrade a little bit.  There is a bit of chromatic
aberration with the TC, but this can be removed with photoshop easily.  The
sharpness is a bit less, but if your prints are not too large it isn't a
problem and photoshop can help a bit here also.

Perhaps others know if the Kenko and Tamron converters are similar.

heathy:

As a general rule, teleconverters only produce good results with lenses
designed for use with a teleconverter. That is because the center of
the image is magnified, and the lense needs to be extra sharp there. A
zoom usually does not have this extra sharpness, and if you use it with
a teleconverter, you get a certain degree of blur in your image.

So there is no cheap way to get this extra reach. Maybe you can find a
used 300 or 400mm prime, and then combine it with a teleconverter.

Thomas

heathy skrev:

Why do you think so? According to this link, it works great´:

http://tinyurl.com/r8n9p

(Scroll way down to the sixth post from bottom, from a user called
"Dante King", and with subject "Kenko 1.4X Teleplus DG Pro 300 TC with
Canon 70-300 DO IS USM".)

Jan Böhme

It is EF, not S.

Canon teleconverters won't fit, but Kenko should fit this lens.

You can try Olympus 1.45x. It goes in the front of the lens. When
stopped down to f/11 (2 stops from wide open), the combo is sharp. And
you keep auto focus.

With a teleconverter that goes behind the lens, with a 1.4x the
aperture is changed from f/5.6 to f/8, and you lose auto focus. If you
stop it down a little to get sharper result, the combo is f/11 (1 stop
from wide open) or dimmer.

http://digitcamera.tripod.com/#slr

It is EF, not S.

Canon teleconverters won't fit, but Kenko should fit this lens.

You can try Olympus 1.45x. It goes in the front of the lens. When
stopped down to f/11 (2 stops from wide open), the combo is sharp. And
you keep auto focus.

With a teleconverter that goes behind the lens, with a 1.4x the
aperture is changed from f/5.6 to f/8, and you lose auto focus. If you
stop it down a little to get sharper result, the combo is f/11 (1 stop
from wide open) or dimmer.

http://digitcamera.tripod.com/#slr