|Wouldnít it be great to recreate some of those beautiful smooth focus pulls seen on TV and in films? Itís difficult to achieve with your Canon lens; after all, itís not what they were designed for. These focusing levers provide a simple but innovative solution.
The easy-to-attach lever allows you to adjust the focus or zoom on your lens in a precise and controlled manner. With this additional control you can achieve smoothness and more gentle transitions. Two levers are provided with each F-Ring, giving you a choice of a long or short lever to suit your preference.
The F-Rings come in size bands and can be fitted to either the focus or zoom ring of your lens. The size refers to the lens diameter, not the filter size. We list the maximum diameter of every Canon EF and EF-S lens in our Everything EOS guide (http://www.eos-magazine.com/Magazine/everything-eos.html), but you will need to make sure that this measurement is consistent with the focus or zoom ring on your lens, as they may not be the widest part.
The most accurate way to measure the diameter of your lens is to use a vernier caliper. Otherwise itís back to school for a maths lesson! Use a tape measure (or piece of string and a ruler) to find out the circumference of your lens at the point at which you want to fit the F-Ring. Divide that measurement by pi (3.14) to find out the diameter of your lens.