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Support Seamless Focus Gear Ring FAQ

How can I measure and find the right focus gear ring for my lens? Last modified 01/10/24

We recommend measuring your lens to get the right fit for your Seamless Focus Gear Ring. It only takes a couple tools and a minute to measure the circumference of your lens and calculate the diameter. Use the calculator at the bottom of this page once you get your circumference measurement.

What is your lens model?

For example, Canon EF 70-200mm 2.8L ISII

What is the perimeter / circumference of the focus ring on your lens?

How to measure perimeter / circumference:

Cover the entire focus gear with a slip of paper and pull the two ends together tightly. Mark down where the two ends meet with a pen. Make sure to mark or be aware of both ends.

measure your lens
Spread the paper slip and find the marks. Measure the distance between the two marks with a ruler in millimeter. For example, 255mm.

Divide 255mm / 3.14 (π ) to get the diameter, which is 81.2mm in this case. The 81-83mm ring size will fit your lens.

Find Your Seamless Gear Size

mm circumference

Contact us with any questions or with your lens name and measurements if you’d like to have it added to our database.

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