Richard Wayne Photography PRO 3:10pm, 7 November 2011
I have an EOS 7D and recently purchased an ef 70-200mm f 2.8l is ii usm lens. I have a question about autofocus procedures for portrait photography using this lens or any zoom lens, for that matter.

Typically, I zoom tight into the face of the subject (200mm) and push the shutter half-way down to set the focus. Then I zoom out to recompose the shot at a shorter focus length, say 85mm, while holding the shutter half-way down, then click the shutter to take the shot.

I have noticed with my new ef 70-200mm f 2.8l is ii usm that it loses focus when I use this procedure. When I zoom out to 85mm or 70mm, the image is blurry. Has anyone else experienced this problem with your zoom lens?

The only way I can get the lens to focus properly at 70mm, is to zoom out to 70mm, then press the shutter half-way down, and then take the shot without recomposing or zooming in or out any further.

By the way, I'm using the spot metering autofocus single-shot mode on my EOS 7D for my portrait photography work. Thanks for your help and advice. I really appreciate it.
amuck lake [deleted] 7 years ago
This is a problem with most zoom lens in general, the focus shifts when you zoom due to the optical elements inside shifting. It's best to focus at 70mm, rather than focus at 200mm and then zoom back to 70mm because of this.
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