Light dirt on a front element often has surprisingly little effect on image quality, so don’t over-clean unless it’s genuinely bad.

For greasy deposits, a mild cleaner that can break down oil is usually more effective than alcohol alone. A small amount of dishwashing liquid can help remove grease, but it’s best only if the glass elements are removed and cleaned separately. After that, a final wipe with pure isopropyl alcohol can help remove residue because it evaporates cleanly.

A dedicated lens cleaner such as ROR is also a good option for very dirty elements; it’s designed to cut greasy film and dry without residue when used sparingly.

Important: avoid getting any cleaner into helicoids, aperture mechanisms, or other moving parts, since those parts need their lubrication. Clean only the glass surfaces, use very little fluid, and work gently to avoid damaging coatings or spreading contamination deeper into the lens.