Using the right technique
Here are the steps you should consider when deciding just how aggressive you should be when cleaning your lens.
1. Check for dust and fingerprints. Do this under good light for both ends of the lens. If you don't see either, you're done. Put the lens cap back on and put the lens back on the camera.
2. If you've found dust: use compressed ("canned") air or a blower brush to try to blow the dust off the lens. Aim the air source from a low angle so it blows dust off the side of the lens rather than into the lens element. If you're using canned air, angle the lens so you can keep the canned air upright otherwise you may shoot solvent onto your lens element requiring even more cleanup. If you've found a fingerprint go to step 4.
3. If some dust remains: use a lens brush to gently whisk the dust off the lens. Use an upward flicking motion rather than dragging the brush across the lens surface.
4. If you've found a fingerprint: take some lens cleaning fluid or isopropyl alcohol and put a drop on the center of the lens (in a pinch, you can just fog the lens with your breath). Then take a microfiber cloth or optical lens tissue (NOT regular facial tissue or toilet paper) or cotton balls and gently move the cleaning fluid around the lens element. Use a circular motion working from the center outward until you reach the end of the circle. Do not press the cleaning material into the lens element, gentleness is the key.
5. If, after all this, your lens is still dirty, throw it out and buy a new one (Just kidding!). Still, if the above steps don't do a satisfactory job of cleaning your lens, it is time to consider professional cleaning through your local camera store or the lens maker.
A couple of other pieces of advice:
- Don't be too aggressive with the cleaning fluid.
- Use too much and you can end up with the excess getting into the lens making things worse.