Re: EOS EF 20-35 with extension tubes

[Jim Davis]

> You may have a problem here. Wide-angle lenses have such small
> depth-of-focus that even a 12mm extension tube may make it impossible to
> focus the lens at all. Try holding the lens partially in the camera's
mount
> and you'll see what I mean. With my Sigma 21-35, even racking the lens out
> by half the depth of the lens mount makes it impossible to focus.
>
> A close-up lens may be your best bet.
>
> Chuck Skinner

    Wide angles have a small depth of focus? HUH?
    Wide angle lenses have inherently large DOF last I checked. If you held
the lens out by hand I guess it was wide open, maybe that gave you a pretty
small DOF...
    I think I need a really small extension tube. Hopefully 12mm will do the
job.



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