How do I measure my lens?

This section will guide you through the measuring process to make sure you select the correct lens gear.

To measure your lens' focus ring circumference, do the following:

1. download one of the ruler files here: US is for US 8 1/2 x 11" paper A4 is for Europe paper size IMPORTANT: Make sure to print out the ruler at 100% size, do not scale to fit.

2. Cut out the ruler and wrap around the focus ring of your lens. Make sure to wrap it around the focus ring, not other parts of the lens such as the filter

3. Record the measurement of your focus ring's circumference. The following chart will help you understand which ring to purchase:

If your lens circumference is within Your Redrock Lens Gear Size is
180mm-220mm 32-A
211mm-250mm 32-B
241mm-280mm 32-C
280mm-320mm 32-D

If your focus ring circumference can be used with more than one Redrock lens gear, you can select either lens gear.


Canon EF Lenses

Here are some common Canon EF (EOS) lenses and their corresponding lens gear size (if more than one is listed, you can use either):

Canon EF Lens Diameter mm Lens gear
14mm f/2.8 L 75 B
16-35mm f/2.8 L  76 B,C
16-35mm f/2.8 L II 76 B
17-35mm f/2.8 L 76 B
20-35mm f/2.8 L 77 B,C
20mm f/2.8 75 B
24mm f/1.4 L 80 C
17mm f/4.0 Tilt Shift Lens 88 C
24mm f/3.5 Tilt Shift Lens 79 B.C
45mm f/2.8 Tilt Shift Lens 78 B,C
90mm f/2.8 Tilt Shift Lens 73 B
24mm f/2.8 67 A
28mm f/1.8 73 B
28mm f/2.8 66 A
24-70mm f/2.8 L 84 C
28-70mm f/2.8 L 83 C
24-105mm f/4.0 L IS 82 C
35mm f/1.4 79 C
35mm f/2.0 67 A
50mm f/1.8 65 A
50mm f/1.4 74 B
50mm f/1.2 86 C
50mm Macro f/2.5 67 A
100mm f/2.0  75 B
100mm Macro f/2.8 USM 79 B,C
100mm Macro f/2.8 75 B
135mm f/2.0 76 B,C
85mm f/1.2 92 D
85mm f/1.8 75 B
70-200mm f/2.8 L 83 C
70-200mm f/2.8 L IS 86 C
100-400mm f/4.5-5.6 L IS 90 D
180mm Macro f/3.5 L 78 B,C
200mm f/2.8 L 75 B