Ever wondered what the fluorine lens coating does on your optics? Why this has typically been a premium coating reserved for professional lenses, often costing thousands of dollars?
Simply put, a fluorine coating is a water- and oil-repellant that is applied to the front element of a lens to a) make it more resistant to liquid and particulates, b) make it easier to clean, and c) protect it from damage due to moisture, dirt, dust and fingerprints.
Not to be confused with fluoride (which protects your teeth from decay, but isn't so useful for protecting your camera lenses!) fluorine compounds repel other atoms. As such, fluorine is one of the key components in non-stick Teflon coatings for kitchen pans – and those same non-stick properties also apply when fluorine is coated on camera lenses.
Not only does this repel oil and moisture in the first place (so, for example, raindrops will slide off the lens element rather than forming droplets), it also makes stubborn particulates (such as fingerprints, mud or grease) much easier to wipe off. As you can see in these demonstration videos from Nikon and Tamron, the coating can protect lenses against everything from water drops to oil paint:
"The coating works in two ways – firstly, it reduces static electricity so that small particles are less likely to be attracted to, and become attached to, the surface. Secondly, it is 'hydrophobic' so it repels moisture and makes cleaning water drops, like rain, off a lens much easier."
That's the explanation from Canon (opens in new tab), which introduced fluorine coatings on the Canon EF 70-300mm f4-5.6L IS USM after using it for years on low-pass filters for DSLR image sensors.
"Cleaning lenses that are coated with fluorine is much easier too. Often you'll find you only need a blower bulb and a soft, dry, cloth to remove any dust that has become attached. In fact, if you use a solvent to clean the lens you may find it harder because the coating will reduce the solvent to very small beads of liquid that are harder to wipe away.
"The fluorine coating is applied over the top of other lens coatings and is added to both the front and rear lens elements as these are the ones most likely to come into contact with dirt."
So the next time you're wondering whether the extra cash is worth it for a fluorine lens coating, you'll know what you're getting!
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