How do I clean a camera lens safely?

Blow, then brush, then wipe — in that order — and the household products that permanently damage lens coatings.

Difficulty: beginner
Time: 10 min
Read: 3 min
Safety: caution

Short answer

Blow the loose dust off first with a blower, then use a soft brush, and only then a microfibre cloth or lens tissue with a drop of proper lens fluid. Wiping first drags grit across the coating and scratches it.

Almost all lens damage from cleaning happens because someone wiped before removing the loose particles. The order of operations is the entire technique.

Safety

Never touch a camera sensor with anything rigid, and never use compressed air cans on a sensor — the propellant can spray liquid onto it. If a sensor mark will not clear with a blower, a professional clean costs less than a replacement sensor assembly. Lens coatings are soft and permanently scratched by grit dragged across them.

What you'll need

A rocket blower
A soft lens brush
A clean microfibre cloth or lens tissues
Proper lens cleaning fluid

Step by step

Blow the loose dust off first.A rubber rocket blower, held with the lens facing down so gravity helps. This removes the grit that would otherwise be dragged across the glass.
Do not use canned air on optics or sensors.It is much more forceful than needed and can eject propellant as a liquid onto the surface. A rubber blower does the job with no risk.
Brush gently next.A dedicated soft lens brush, used lightly, for anything the blower left. Keep it in a case so it does not collect grit itself.
Only then wipe.A clean microfibre cloth or a lens tissue, in gentle circles from the centre outwards. Fresh cloth every time; a cloth carrying grit is a scouring pad.
Use fluid on the cloth, never on the lens.One or two drops on the cloth. Liquid applied directly can run into the barrel and reach the internal elements and electronics.
Use the right fluid.Proper lens cleaning fluid, or nothing. Household glass cleaner, alcohol wipes and washing-up liquid can strip or cloud the anti-reflective coatings, which is irreversible.
Clean the rear element and contacts carefully.The rear element affects image quality more than the front. Wipe the electrical contacts with a dry cloth only.
Blow the sensor, and stop there.Use the camera's sensor cleaning function, then a blower with the camera facing down. Anything beyond that — swabs and fluid — is easy to get wrong and a professional clean is not expensive.
Work out whether marks are on the sensor or the lens.Photograph a plain white surface at f/16. Dark spots in the same place across different lenses are on the sensor; marks that move with the lens are on the glass.
Prevent rather than clean.Lens caps on, a bag that closes, and change lenses facing down and out of the wind. Most cleaning is avoidable.

Tips

Blow, brush, wipe — in that order, every time.
Fluid on the cloth, never on the lens.
A little dust on the front element has essentially no effect on the picture. Fingerprints and smears do.

Common mistakes

Wiping the lens with a shirt or a tissue — Fabric and paper tissue carry grit and are abrasive, and the coatings on modern lenses are soft. The result is a permanent network of fine scratches that reduce contrast.
Using household glass cleaner — Ammonia and other solvents attack anti-reflective coatings, producing cloudy patches that cannot be removed and permanently degrade the image.

If it doesn't work

Hazy, low-contrast images

Cause: Smeared front element or a cheap filter — Fix: Clean properly with lens fluid, and remove any low-quality filter.

Same dark spots on every photo

Cause: Dust on the sensor — Fix: Run the camera's sensor clean, then use a blower. If it persists, have it professionally cleaned.

Fine scratches on the front element

Cause: Wiped without removing grit first — Fix: Not repairable. A clear protective filter prevents recurrence, and light scratches affect images less than people fear.

Fungus-like threads inside the lens

Cause: Stored damp and dark — Fix: Needs professional attention. Store lenses somewhere dry and occasionally in daylight to prevent it.

Questions people ask

Should I keep a UV filter on for protection?

It is a trade-off. A good filter protects the front element at a small cost in flare; a cheap one visibly degrades the image. A lens hood protects nearly as well and improves contrast.

Does dust inside the lens matter?

Usually far less than people expect. A few specks inside have essentially no visible effect. Fungus does matter, because it etches the coatings over time.