Everything to Know About Camera Lens Fungus

Lens fungus is the mycelium growth of water molds and sac fungi. There are tens of thousands of species.

That’s why fungus can look different, It can look like thin wispy cotton threads, small spots, or a large piece of dust. This can make identification tricky.

A small amount will likely not show up in images. Large amounts can ruin a lens by etching the glass.

Fungus can grow on the surface of a lens, prism, viewfinder, sensor filters, mirrors, or other optics. They feed on organic matter, such as dust, oils, and some older optical coatings.

Avoid Growth Conditions

Avoid these conditions. They can happen in a camera bag, basement, attic, or dark room.

The rule of thumb is, if you wouldn’t be comfortable, it’s a bad place to store camera gear.

Fungal Growth Conditions: (According to Zeiss)

• Relative humidity of 70% or higher
• Little to no air movement
• Darkness
• Temperatures between 10°C and 35°C (50°F to 95°F)

How to Prevent Lens Fungus

In the tropics, or if you experience humid summers, a dry cabinet is the answer.

There are commercially available cabinets designed for cameras and lenses.

A DIY option can be as simple as a plastic bag and silica gel packets while traveling.

There are different desiccants that can be used with a plastic container. Some will even show when it’s been saturated.

Silica gel can be reused after heating it, to release the moister it trapped. A plastic container that seals and a

Fungus will not grow:

• 30% to 60% relative humidity. (Too low can cause problems.)
• 40°C to under 50°C (Dry cabinets can use heaters.)
• Light and ventilation.
• Lenses and gear should be clean and dry. (Microfiber cloth to clean.)

Image Quality?

Minor lens fungus might not be noticeable in images. It will be less noticeable on lens elements that are closer to the front.

Larger amounts of fungus will reduce contrast and sharpness. If the fungal growth is bad enough, parts of the image can be blocked.

Types of Dry Cabinets

Dry cabinets will prevent fungus from growing. They’re the ideal place to store camera gear.

Electronic Dry Boxes

Electronic dry boxes have, surprise surprise, electronically controlled humidity. They will often have a digital hygrometer to monitor and display the humidity level.

They can heat and circular air. Some have lights and locks.

They’re available in all different sizes.

Desiccant Dry Boxes

These dry boxes are easy DIY solutions as all that is needed is an airtight box and desiccant. For travel, a bag and silica gel packets can be used.

Desiccant will get saturated with water over time. It does not need to be replaced. The moisture can be removed by sticking it in a warm oven.

Auto parts stores will have containers designed to be reused. Just follow the instructions.

Cleaning and Removing Fungus

Cleaning and removing fungus from a lens requires disassembly. There is also no guarantee removal will fix the problem as the fungus can etch glass.

It can be difficult to find someone willing to clean lens fungus. The most often situation is where the cost of repair is more than the cost of replacement.

The outer front and rear elements of lenses can be surprisingly easy to remove. Often only lock rings and possibly a few screws hold them in place.

The closer the fungus is to the aperture, the more difficult it will be to remove. The more technology and newer a lens is, the more difficult it will be.

How to Clean and Remove Fungus

First, you have to disassemble a lens to get to the elements with the fungus.

Front and rear elements can be very easy to remove. It can be as simple as unscrewing them.

The name plates of lenses are easy to remove with a rubber “wrench”.

I’m not going to give a tutorial, but here is what I’ve used:

• JIS Screwdrivers
• Lens Spanner
• Rubber Retainer Ring “Wrenches”
• Lint Free Tissues
• Nitrile Gloves
• Naphtha (lighter fluid)

Naptha is dangerous. It’s a powerful solvent. Safety precautions are a must.

It is highly flammable. It produces strong fumes. You need to have active ventilation.

Gloves and eye protection need to be worn.

I would suggest first trying isopropyl alcohol. That can be enough to remove the fungus or mold from a lens element. It’s also less likely to damage a lens coating.

When that wouldn’t work is when I would bust out the lighter fluid. Keep in mind that the element might be etched. Mycelium growth is like tree roots tearing up a sidewalk.

Other Types of Camera Lens Damage

Balsam Separation

Balsam separation is where the bond between lens elements begins to delaminate. Historically, Canada balsam was used, which came from the balsam fir tree. Hence the name.

It will look like white or powdery spots. On old and poorly stored lenses, elements can completely separate.

Modern lenses use epoxies, but those can also delaminate. If the lens elements have coatings, the separation will look like a rainbow reflection.

Haze

Lens haze is where the optical clarity of a camera lens is blocked with minute particles, often dust, or moisture. This can result in photos with reduced contrast, a foggy or milky appearance in images, or a general lack of sharpness.

Mild haze may not noticeably affect image quality, where as severe haze can render a lens practically unusable.

A common cause is exposure to hot temperatures, like being left in a sunny car during summer. The high temperatures can allow liquids such as lubricants vaporize, which get deposited on lens elements when the temperature drops.