Canon EOS Tele-convertor lenses

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I have seen advertised tele-convertor lenses for Canon EOS lenses. As they are about £ 75 ($ 105), it seems a cheap way of increasing your zoom power. Are they any good? Is it worth it?

I base my assumption on a x1.4 convertor with my 70mm to 210 mm zoom which would give me a 100mm to 300 mm (ish) lense. Or can someone tell me where to buy a similar lense for the same money?

-- bill quinn (bill.quinn@btinternet.com), September 18, 2001

Answers

A £75 TC is not going to be worth buying. If you look at the Canon lens range, you'll see that they sell teleconverters, and that there are not many lenses that they can be fitted to (ie generally only the telephoto L series lenses). There's a good reason for this.

The original lens used needs to have a high level of resolving power, because you're magnifying the fine details, and can't add in any more resolving power. See the teleconverter as taking the middle section of the picture the lens gives, and blowing it up 1.4 times, cropping off the edges.

AF operation will also start to become a worry, because (at a guess) a 70-210 is F3.5-4.5, which will drop to 4.5-6.7 with a 1.4X TC, and that will not AF reliably. If the 70-210 is F4-5.6, then you really will run into AF problems, as it will drop to F5.6-8.

A much better solution would be to sell your 70-210 and buy a 70-300 (eg Sigma 70-300mm APO Macro). This will give you much better results than any consumer zoom + consumer TC combo, as well as a faster lens (F4-5.6) and less hassle over changing lenses and teleconverters.

I have a mint Sigma 70-300 APO Macro for sale at the moment, so if you want to go that way...;-).

-- Isaac Sibson (Isibson@hotmail.com), September 19, 2001.


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