Lens filters are optical accessories that change light before it reaches your sensor. To choose well, work out which effect you actually need, then match the filter size, build and optical quality to your lens.
Common Filter Types
Each type has a distinct job, and some are hard to imitate in editing software.
- Clear or UV filters: a thin layer of glass over the front of a lens.
- Circular polarizers: reduce reflections and deepen skies when turned correctly.
- Neutral density (ND) filters: cut light evenly so you can use long exposures or wide apertures in bright conditions.
- Graduated ND filters: darker on one half, to balance a bright sky with a darker ground.
- Colour and effect filters: mostly replaced by editing, though still used by some.
Getting the Size Right
Screw-in filters match the thread diameter of your lens, shown in millimetres on the front or inside the cap. Some people buy a filter for the largest lens they own and use step-up rings for smaller ones. Square filters use holders that fit many lenses with adapters.
Check the maker’s guide to confirm thread size, because a near match will not fit.
Quality and Build
A filter sits in front of all your lens glass, so poor quality can lower sharpness, add flare or cause colour casts. Look for clean glass, good coatings and a slim frame if you use wide lenses, to avoid dark corners.
- Check for coatings that resist smudges and reflections.
- Inspect the frame for smooth threads and a tight fit.
- Read the maker’s description of colour neutrality for ND filters.
- Keep a cloth and a cap case so filters stay clean.
Which Filter for Which Job
| Goal | Filter type | Note |
|---|---|---|
| Cut glare on water or leaves | Circular polarizer | Rotate to adjust the effect |
| Blur moving water in daylight | ND filter | Use with a tripod |
| Balance sky and land | Graduated ND | Place the edge on the horizon |
| Basic front glass guard | Clear filter | Choose good coatings |
Care matters too. Fingerprints and dust on a filter show up in pictures just as they would on the lens, so carry a soft cloth and a blower. Store filters in cases to avoid scratches on coatings, and keep a spare clear ring or cap for the thread. If a filter gets stuck on the lens, do not force it; ask the maker or a repair shop how to remove it without damage.
FAQ
Do I need filters at all?
Not always. Polarizers and ND filters give effects that are hard to copy later, while other types are optional.
Can stacking filters cause problems?
Stacking can add flare and darken the corners on wide lenses. Use as few as you can.
The Short Version
Choose filters by the effect you want, buy for your lens thread size, and favour clean glass with good coatings. A polarizer and an ND filter cover most needs for outdoor photography.
