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petrus Nov 15, 2003 11:50 AM

Teleconverter for EOS300D
I have the 75-300 Zoom USMIII qnd wonder if a TC does this lens any good. Sometimes a longer lens would be nice to have... Is there any major diff between Canon original and Sigma/Tamron etc? :?: :?:

NHL Nov 15, 2003 12:06 PM

Try them out 1st. Usually with a TC you'll double the aperture hence kill the AF in the camera and end up having to manual focus the lens/TC combo! :wink:

... there's trick in masking a few pins, but the the AF will still hunt and a 300mm @ f/8-11 is usually too slow for the shutter... May be a 1.4x TC is a better buy, or an f/2.8 lens is more valuable for this purpose :?

ursa Nov 15, 2003 8:42 PM

with a 2x TC thats a lot of lens - effectively you'd have a 1020mm lens! But with a maximum aperature of f11 (full zoom) you'll have a hard time with AF and keeping the shutter speed up to minimize camera shake, even with a tripod.

Do you really need that much lens? I'd stay with a 1.4X TC.

petrus Nov 16, 2003 5:30 AM

Thanks a lot! There was something for me to think about!! :)

eric s Nov 16, 2003 10:04 PM

Something else to think about.

Not all lenses can take the Canon TCs. They have a protruding element which can hit a lens that had an element near the back. So you might not be able to put a Canon TC on that lens. I don't have a list of what Canon lens can take a TC, but a quick look at your lens should give you a general idea. Also, any reputable full service photo store should be able to tell you.

I've heard good things about the Kenko teleconverters. Something to think about.

Ursa is right, you'll need a really good tripod & head, along with good long lens technique to get good shots out of 1020mm.


petrus Nov 17, 2003 1:03 PM

Thank you eric s. There really doesn't seem to be many lenses possible to use with Canon's TC.
Is the construction of Kenko/Sigma and others different?

eric s Nov 17, 2003 8:38 PM

Yes, at least the Kenko is different (from what I've been told) and will work with a much wider range of lenses.

I've heard quite good things about the Kenko TCs. I've never used one (I have the Canon 1.4TC) but I've read many good things about them.


NHL Nov 17, 2003 10:08 PM

... Actually there's two types of TC:

o General purpose TC - for general use, ie Kenko as well as others...
o Matched TC - optimized for certain lenses or range of lenses. The Canon, Sigma and Tamron are all matched.

Generally the matched TCs are better optically since they are designed to work precisely with only certains lenses... and do not have to covered an entire range! :wink:

kartracer Dec 4, 2003 7:31 AM

[quote="NHL"]Try them out 1st. Usually with a TC you'll double the aperture hence kill the AF in the camera and end up having to manual focus the lens/TC combo! quote]

I have a Sigma 28mm /f1.8. I got it specifically for the AF being 1.8. I'm currently looking at a used 2x TC so that I can have a bit more zoom instead of getting the 50mm /f1.8. If I do end up getting this TC, can some one tell me what exactly will it do to my AF on this lense. I got this lens to shoot moving objects indoors with poor light.

NHL Dec 4, 2003 7:43 AM

f/1.8 will become ~f/4 with a 2x; slower but fast enough to preserve the AF, but do you really want to do this?

A $70 EF 50mm /f1.8 is usually cheaper than a high quality 2x and still gives you the large aperture (for that indoor shot that you need)! It's not much bigger(or heavier) than a 2x, but is much better optically than the above combo with better de-focus DOF too... :wink:

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