How can I find which lenses have “Continuous manual focus”?

Question

Canon lenses with USM auto focus can be called "continuous manual focus" (at least some). By this I mean that you can override the AF without switching it off. I've found this very handy, and I often miss this option when it's not there.

I know Sigma have HSM AF on several lenses, but I've encountered at least one of these which still requires me to "turn off" AF with a switch before I can manually focus. Does anyone know where I can find a comprehensive list over lenses from Sigma (and others) which have "continuous manual focus"?

Answer

This is known as full-time manual focus override (FTM).

If you look at the Sigma product catalogue (PDF) it mentions within each lens description if it has that feature.

Tokina AT-X PRO series lenses have what they call a Focus Clutch mechanism that allows you to override the AF. The only lens I'm familiar with is the 11-16mm f/2.8 which has this feature.

The only Tamron lens I know of is the 70-300mm Di VC. The 17-50mm VC unfortunately doesn't have it.

Canon USM lenses have the feature as pointed out in the original post.

Nikon AF-s lenses have the feature. Set a switch on the lens to M/A and you can manuall override focus.

You may need to have your camera's autofocus setting to single AF rather than continuous servo (or whatever your brand may call it) otherwise it will not let you adjust, or will override your manual adjustment.

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