Canon Lens Extender

Started Dec 26, 2012 | Questions thread
Michael Fryd
Senior MemberPosts: 1,723
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Re: Canon Lens Extender
In reply to tonyjr, Dec 31, 2012

tonyjr wrote:

The 2X with my 70-200mm / 2.8 work fine on my 7 D in low light . I use for candid shots at wedding receptions and parties - not a fan of canned smiles . And yes if you were wondering , I have a UV filter on the lens .

According to my 7D Manual, with an f/2.8 lens, all 19 focus point operate as cross-type AF sensors (sensitive to horizontal or vertical lines).  Also the center point operates in high precision mode, and is about twice as sensitive as the other focus points.

When you put the 2X teleconverter on the 70-200 f/2.8 lens, 12 of the focus point lose their cross-type capabilities and become horizontal or vertical line sensitive only.  Furthermore the central point drops out of high-preceision mode.  The manual for the 70-200 f/2.8 recommends that when using a tele-extender, you only use the central focus point.

Even with these disadvantages, there are clearly times when a tele-extender is the right solution.

Tele-extenders are documented as reducing quality.  With a good lens, and a good tele-extender, this reduction is minimized, and you can still get very good results.

The same is true for filters.  Under some circumstances they will not be a problem, and in other circumstances they can render a shot unusable.

I am glad to hear that you are happy with your image quality, and have no issues.

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