Why This Matters When Buying Used Lenses

When you browse used lenses, you’ll often see terms like “minor haze,” “slight fungus,” or “clean optics.” These small details can make a huge difference in image quality and lens value.

Knowing how to spot and understand these conditions helps you avoid lenses that could ruin your photos — or your wallet.

Let’s break down the two most common issues: lens haze and lens fungus.

What Is Lens Haze

Lens haze is a fog-like film or cloudiness that forms inside a lens, usually caused by evaporated lubricants, aging coatings, or moisture residue on internal glass elements.

It can appear as a soft, diffuse glow when you shine a light through the lens. In some cases, it looks like fine mist or smoke trapped behind the glass.

Causes of Lens Haze

• Old grease or oil from the focusing helicoid evaporating over time.

• Condensation from storage in humid or fluctuating environments.

• Fading or deterioration of anti-reflective coatings.

How Lens Haze Affects Image Quality

• Reduced contrast and color saturation.

• Slight glow around highlights.

• Softness, especially when shooting into bright light.

Can Haze Be Cleaned

Yes, in most cases.
A skilled technician can disassemble the lens, clean internal elements, and restore optical clarity. If haze is mild and only on the surface, it can often be removed completely.

However, if it’s caused by coating degradation, cleaning may not fully restore performance.

What Is Lens Fungus

Lens fungus is a living organism — a type of mold — that grows inside lenses when they’re stored in dark, humid environments.

It feeds on organic materials such as lubricants, dust, and even optical coatings.

When you shine a flashlight through a fungus-affected lens, you’ll see thin, web-like threads or spots, often starting from the edges of glass elements and spreading inward.

Causes of Lens Fungus

• High humidity and poor ventilation during long storage.

• Dust or organic material left inside the lens acting as food.

• Lack of use — lenses that sit untouched for years are more vulnerable.

How Lens Fungus Affects Image Quality

• Early-stage fungus may cause little to no impact.

• Advanced growth can etch the glass surface, permanently reducing sharpness and contrast.

• Severe cases create uneven flare or ghosting in bright light.

Can Fungus Be Removed

Sometimes.
Cleaning early-stage fungus can be done with specialized solutions or UV light, but if the fungus has etched the glass or coatings, the damage is permanent.

Fungus can also spread to other lenses if stored together, so infected gear should be isolated immediately.

Lens Haze vs Fungus: Key Differences

How to Check for Haze or Fungus Before Buying

1. Shine a Light Through the Lens

Use a small flashlight or your phone’s LED. Look through the rear element at an angle.

• Haze looks like a foggy layer or soft glow.

• Fungus looks like threads, spiderwebs, or tiny branching patterns.

2. Check Around the Edges

Fungus often begins at the edges where moisture collects. If you see white or gray filaments creeping inward, it’s a warning sign.

3. Ask for Backlit Photos

When buying online, request a clear backlit image of the lens. Honest sellers usually provide this. If a seller refuses, proceed cautiously.

4. Look for Coating Damage

Even if fungus is gone, etched coatings leave rainbow-like marks or dull patches on the glass — these cannot be repaired.

5. Smell the Lens

A strong musty or earthy odor can indicate past fungal growth or poor storage conditions.

Bonus Issue: Balsam Separation

Sometimes what looks like haze is actually balsam separation, where the optical cement between lens elements begins to separate.

This creates rainbow patterns or edge halos, especially in older lenses made before modern bonding methods. Unlike haze, balsam separation cannot be fixed without major reconstruction.

If you see colored rings or reflective patterns between elements, it’s best to avoid that lens.

Should You Buy a Lens With Haze or Fungus

• Minor haze: Often safe to buy if the price is right. Cleaning usually restores performance.

• Light fungus: Only worth it if you plan to service it immediately and the price is heavily discounted.

• Heavy fungus or etching: Avoid — it’s a sign of permanent damage.

• Combination of haze and fungus: A red flag for poor storage history.

When in doubt, always ask for return policies or inspection options before committing to a purchase.

FAQs About Lens Haze and Fungus

Is haze less serious than fungus?
Yes. Haze is usually caused by residue and can often be cleaned, while fungus may permanently damage glass.

Can a lens with fungus infect my other lenses?
Yes. Fungal spores can spread in humid storage conditions. Keep affected lenses isolated.

How can I prevent haze and fungus?
Store lenses in a dry, ventilated area with silica gel or a dehumidifying cabinet.

Does sunlight help kill fungus?
UV light can slow or stop fungal growth, but it won’t repair etched glass.

Can professional cleaning restore a hazy lens completely?
Often yes, unless the haze comes from coating damage or separation between elements.

Conclusion: Know What You’re Buying

When shopping for vintage lenses, haze is usually manageable — fungus is often not.

A little internal haze might slightly reduce contrast but is rarely a dealbreaker. Fungus, however, can permanently scar optics and spread to other lenses if ignored.

Before buying any used lens, inspect carefully or request detailed photos under strong light. Knowing what you’re looking at can save you hundreds of dollars and a lot of disappointment.