Kit planning
Lens filter size planner
Add your lenses and the filters you own. The planner finds the size that fits everything with step-up rings, and says which filters fit directly.
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3 lenses for the EOS R50
Buy 55 mm filters
They fit RF-S55-210mm F5-7.1 IS STM directly, and the rest through 2 step-up rings.
- RF-S10-18mm F4.5-6.3 IS STM: 49–55 mm step-up ring 49–55 mm ring on Amazon
- RF-S18-45mm F4.5-6.3 IS STM: 49–55 mm step-up ring 49–55 mm ring on Amazon
| Lens | Thread | Your 55 mm |
|---|---|---|
| Canon RF-S10-18mm F4.5-6.3 IS STM | 49 mm | With a 49–55 mm ring |
| Canon RF-S18-45mm F4.5-6.3 IS STM | 49 mm | With a 49–55 mm ring |
| Canon RF-S55-210mm F5-7.1 IS STM | 55 mm | Fits directly |
ND filters: the shutter speed you need
Meter the scene without the filter, then choose the filter: the answer is the shutter speed to set with it on, at the same aperture and ISO.
Metered at 1/125 s, with the ND1000
Expose for 8 s
It passes 1/1,000 of the light, about 10 stops, so the shutter stays open 1,000 times as long.
From about six stops the picture on the screen and in the viewfinder turns dark: frame and focus first, switch to manual focus, then fit the filter.
| ND number | Optical density | Stops | Light passed | 1/125 s becomes |
|---|---|---|---|---|
| ND2 | 0.3 | 1 | 1/2 | 1/63 s |
| ND4 | 0.6 | 2 | 1/4 | 1/31 s |
| ND8 | 0.9 | 3 | 1/8 | 1/16 s |
| ND16 | 1.2 | 4 | 1/16 | 1/8 s |
| ND32 | 1.5 | 5 | 1/32 | 1/4 s |
| ND64 | 1.8 | 6 | 1/64 | 0.5 s |
| ND128 | 2.1 | 7 | 1/128 | 1 s |
| ND256 | 2.4 | 8 | 1/256 | 2 s |
| ND400 | 2.6 | 8.6 | 1/400 | 3.2 s |
| ND1000 | 3.0 | 10 | 1/1,000 | 8 s |
| ND32000 | 4.5 | 15 | 1/32,000 | 4 min 16 s |
How step-up rings work
A step-up ring screws into a smaller lens thread and takes a larger filter, so one set of filters fits several lenses. Rings only go up: a filter smaller than the lens thread would darken the corners. With a ring fitted, the lens's own hood usually will not fit, and a cap needs the filter's size.
Facts from the makers' specification pages. How we check