One speck on the front element does not demand vigorous polishing. Fingerprints, salt spray or a broad greasy film can matter more, particularly in backlight. Inspect the surface under angled light and decide whether cleaning is needed. Repeated dry rubbing on dirty glass can cause more harm than a small unobtrusive amount of dust.
Remove loose particles without rubbing
Work in a clean, calm place. Start with a suitable hand blower to remove loose particles. Keep its tip away from the glass. Do not blow with your mouth because moisture and saliva can reach the surface. Canned compressed air is not an equivalent substitute for a simple blower.
Inspect again for remaining attached dirt. A cleaning tool that has collected sand in an open bag is unsuitable. Store cloths and brushes protected and do not use the same ones for dirty camera bodies and optical surfaces. A cloth that looks clean can still contain small hard particles.
Lift grease and smears carefully
For attached marks, use a cleaning product suitable for the optical coating and a clean intended cloth according to manufacturer instructions. Do not apply liquid uncontrollably to the lens where it can run into edges and seals. Use little pressure and repeat a gentle pass rather than scrubbing firmly.
Household cleaners, kitchen paper or a used sleeve are not dependable choices for coated optics. If a protective filter is mounted, check whether the dirt is on it rather than the front element. Even a clean filter can add reflections in backlight; a comparison without it helps distinguish cleaning from optical effects.
Know the limits of cleaning
Do not dismantle a lens to remove internal dust. Internal haze, suspected fungus or damaged coatings need assessment by an appropriate service. Sensor cleaning is also a different procedure from wiping a front element. After cleaning, replace the cap and use a normal photograph to check whether the original problem has disappeared. More rubbing without a visible reason does not automatically improve the image.
