The glass of most modern camera lenses is coated (or multicoated) with special chemicals to increase contrast and decrease dispersion of light as it goes from the air into the glass.  Both the glass and the coatings are easily scratched, and some chemicals may remove the coatings.  Keep dirt off your lenses, but if they become dirty, here is what to do:

There are 3 main ways to clean lenses - with dry "lens pens", with special dry cloths, and with cleaning fluid and cloths.  Whatever method you will use, the first steps are always the same:

  1. With the front and rear lens caps on, wipe any dirt off the lens with a clean cloth.  If necessary, the cloth may be dampened with water.
  2. Remove the front (or rear) lens cap.  Holding the exposed lens surface facing down, blow across the surface to dislodge as much dust as possible.
  3. Carefully use a lens brush (or a blower-brush) to remove any remaining dust.  Again hold the lens with the glass facing down so that dislodged particles fall away from the glass.
  4. Turn the lens glass-up in good light.  Examine it carefully for spots and any remaining dust.  Tilt it from side to side to change the light and highlight any remaining dirt.
  5. Be sure you have removed all dust and grit.  If you fail to do so, the next steps will ruin the coatings on your lens.

At this point, your lens may well be clean.  Do the following only if there are visible spots (oil, water, fingerprints) on the lens surface.

Using a lens pen:

  1. Follow the instructions on the pen.  Usually, this involves gently rubbing any spots on the lens with the rubberized end of the pen (which flakes off in tiny particles).
  2. When the spot is removed, invert the lens and brush it clean using the steps above.

 

Using a dry cloth: 

(note - these are special cloths sold in camera stores.  some high tech bandanas and handkerchiefs are made of similar material, however):

  1. Breathe on the lens to fog it slightly and polish the glass with the cloth.  Use small circular motions.
  2. If the cloth becomes dirty, wash it according to instructions.

 

Using a cleaning solution:

(note - be sure to get lens cleaning solution that is compatible with the multicoatings on camera lenses.  Window cleaners, alcohol, and some eyeglass cleaners will remove or damage the coatings):

  1. Place a few drops of the solution on a clean, lint-free cloth.
  2. Use the cloth to gently polish the spots, working in small, circular motions.
  3. Stubborn spots may require more fluid, perhaps even a small drop placed right on the spot.
  4. With the spots removed, gently polish away any remaining streaks using a clean dry lint-free cloth.