2X Extender/convertor

[mark_razler]

<p>Can you use a 2x extender with a Canon 40d and a 70 -300 IS USM f4-5.6 zoom lens</p>

[jeff_bubis]

<p>Yes, but AF won't work.</p>

[alan_bryant1]

<p>The Canon extender won't mount on that lens. You could probably mount a third-party extender - from Kenko, Tamron, Sigma, etc - however the aperture will be dismal (f/8 to f/11), autofocus won't work, and the viewfinder will be very dark.</p>

[elliot1]

<p>This is a link to a list of compatible lenses with the extender:</p>

<p>http://reviews.ebay.com/Canon-1-4x-and-2x-Extender-Compatibility-List_W0QQugidZ10000000002121088</p>

<p>IQ will be unacceptable with any converter you use with this combo and have the issues Alan lists above.</p>

[bobatkins]

<p>If you stick with a 1.4x 3rd party TC (like the Tamron), the image quality isn't bad. With a 2x it would likely be pretty poor. Don't get greedy, stick with the 1.4x if you want a little longer focal length.</p>

<p>I've got a couple of sample images using a 1.4x TC with the 70-300is at <a href="http://www.bobatkins.com/photography/reviews/canon_EF_70-300_II.html">http://www.bobatkins.com/photography/reviews/canon_EF_70-300_II.html</a></p>

[mike_hitchen]

<p>I have used the Tamron 1.4x tc on that lens with the 30D. The autofocus does work but will only be really effective in good light where you can use an aperture of f5.6 - it sort of works at f8 but can hunt a lot. On the 30D I found no problem manual focussing even in overcast conditions. Bob's comment backs what I have read selsewhere that when considering the cost-zoom-quality matters, the 1.4x seems to be a better bet than the 2x (of any manufacturer).<br>

Alan - I thought the 2x physically fitted on the lens but just did not retain AF.</p>

[alan_bryant1]

<p>I don't have either one, so I can't say from experience if they fit or not. But I do have the Canon 1.4x, and I know it doesn't fit on lenses which are perfectly capable of having an extender - like my Sigma 150/2.8 macro. The Canon extender doesn't fit because the glass portion actually extends some distance outside of the extender tube, toward the lens. So, the lens has to have a cavity sufficiently large to contain that glass. I don't know about the 70-300, but many lenses do not have that space. Third-party extenders are smaller and fit more lenses.</p>

[philip_wilson]

<p>Your better option is probably to spend slightly more and buy a longer lens You can find used Tamron and Sigma lens that will work well (e.g. 170-500, 200-500 etc...) for about $500 ish. this is about $200 more than the TC but is a much better solution.</p>

[mike_hitchen]

<p>Hi Alan - you were correct. Bob's review of the 70-300 specifically mentioned that it did not physically fit that lens. Lord knows which Canon engineer designed that one!</p>