Buying guide ยท Lenses
Should You Buy a Vintage Lens With Fungus or Haze?
Read enough vintage lens listings and you'll start to see the same phrases: "light fungus", "slight haze", "some cleaning marks", "does not affect images". Some of those lenses are bargains. Others are expensive lessons.
This guide explains what each glass problem actually is, how to spot it, how much it's likely to matter for your pictures, and when a flawed lens is still a smart buy.
:How to inspect a lens properly
You need a bright, small light source and a dark-ish room. A phone flashlight works; a dedicated LED penlight is better.
- Open the aperture fully (on lenses with an automatic aperture, hold the stop-down lever or set the aperture lock if there is one).
- Set focus to infinity and then to close focus while you look, because the elements move.
- Shine the light through from the rear and look in from the front at an angle. Then reverse it.
- Tilt slowly so the light catches each surface in turn. Haze shows as a uniform glow; fungus as threads or spots; dust as specks.
- Check without the flashlight too, by looking through the lens at a bright window. Heavy haze makes the whole view look veiled.
What you're looking at
| Defect | What it looks like | Effect on images | Fixable? |
|---|---|---|---|
| Dust | Specks scattered on or between elements | Usually none visible | Not usually necessary |
| Fungus | Branching threads, spider-web or snowflake shapes, often starting at the edge | Light: minimal. Heavy: lower contrast, flare | Often cleanable; etching may remain |
| Haze | Even fog or milky film across a surface | Lower contrast, more flare, glow around highlights | Surface haze often cleanable; some is permanent |
| Separation | Rainbow-coloured or milky patches spreading from the edge of a cemented pair | Flare and contrast loss | Specialist re-cementing; often uneconomic |
| Cleaning marks | Fine circular scratches in the coating | Usually minor; possible flare | No |
| Scratches | Distinct lines in the glass | Small front scratches: little effect. Rear element scratches: more effect | No |
| Yellowing | Warm tint looking through the lens | Colour cast | Sometimes reduced with UV exposure |
| Bubbles | Tiny round spheres inside the glass | None; a normal feature of some older optical glass | Not needed |
Fungus: the one to take seriously
Lens fungus grows when lenses are stored in warm, humid, dark, still air. Closets, damp basements and leather cases are classic culprits. Over time, the fungus can etch into the lens coatings or even the glass, leaving permanent marks once it's cleaned away.
How much does it matter?
- A small spot at the edge of one element may have no visible effect on images.
- Several patches or webs across an element will usually reduce contrast and increase flare.
- Fungus on several surfaces suggests long, poor storage, and the chance of coating damage is higher.
As a precaution, many collectors store fungal lenses away from clean gear until they're cleaned.
Haze: the ambiguous one
Haze can have several causes. Lubricant from the focusing helicoid or aperture mechanism can evaporate over time and condense on inner surfaces as a film. That kind of haze can often be cleaned off by a repairer. Other haze comes from changes in the glass or coating itself and doesn't clean.
From the outside you often can't tell which kind you've got. A lens with heavy haze is a gamble unless the price reflects the worst case.
Separation and the specialist repair
Many lenses include elements glued together. Older lenses often used natural balsam cement, which can fail with age or heat. Separation looks like rainbow-coloured or milky patches spreading from the edge. Fixing it means splitting the elements, cleaning them and re-cementing, which is specialist work, and for most lenses it costs more than the lens is likely worth. Treat a separated lens as a display piece unless it's rare and the repair makes sense.
When a flawed lens is still worth buying
Yes, probably
Dust, light cleaning marks, bubbles, a tiny fungus spot at the edge, priced accordingly.
Maybe
Light haze or fungus on a common lens at a low price, if you'll have it cleaned or enjoy a softer look.
Only as a project
Heavy fungus, heavy haze or separation, unless the lens is rare and you know what repair involves.
The guiding rule: price a flawed lens as if it will never be fixed. If cleaning works out, that's a bonus. If you're thinking of reselling later, disclose every flaw honestly.
Lenses described as having fungus or haze show up on marketplaces regularly. Read the description closely and ask for photos with a light behind the lens.
Getting a flawed lens cleaned
If you buy a lens with fungus or internal haze, cleaning means taking it apart. That's work for a repairer with the right tools, especially on lenses where element spacing and centring affect sharpness. Before you send it off, ask for an assessment rather than a fixed promise. A technician can tell you after opening the lens whether the fungus has etched the coating, whether haze is a removable film or a glass change, and whether separation is present.
Weigh the cost of cleaning against the lens. For a common, inexpensive lens, buying a clean example is often more sensible. For a rare or optically special lens, or one with sentimental value, cleaning can be well worth it even if some marks remain.
Avoid home remedies that involve opening a lens without experience. It's easy to scratch coatings, lose a spacer, or reassemble an element backwards, all of which do more harm than the original flaw. Outer surfaces are a different matter: a blower, a soft brush and lens tissue are safe for the front and rear glass.
Questions to ask a seller
- Can you photograph the lens with a flashlight shining through it from behind?
- Is there any fungus, haze, separation or scratches on any element?
- Do the aperture blades move freely, and are they free of oil?
- Does the focus ring turn smoothly through the full range?
- How has the lens been stored?
- Can you share a sample image taken with this lens?
Keeping your lenses clean
Once you own a clean lens, keep it that way. Store lenses in a dry, ventilated place, not in sealed leather cases or damp rooms. Many collectors use a dry cabinet or a container with silica gel and a hygrometer. Use your lenses: light and air circulation discourage fungus. Clean the outer glass only with a blower, a soft brush and lens tissue, and never take a lens apart unless you know exactly what you're doing.
The bottom line
For most people, dust and minor marks are fine, light fungus or haze is a price discount, and separation is a pass unless the lens is special. Inspect with a light, ask for photos, and pay for the lens as it is, not as it might be after a repair.
Frequently asked questions
Does lens fungus spread to other lenses?
Fungus spores are everywhere already, and growth depends mainly on humidity and storage conditions. Even so, many collectors keep fungal lenses separate from clean gear as a precaution, and everyone benefits from storing lenses in a dry, ventilated place.
Can lens fungus be cleaned?
Often the fungus itself can be removed by a repairer who disassembles the lens. But fungus can etch the lens coating or glass, and those marks remain after cleaning. Whether cleaning is worthwhile depends on the lens and how far the fungus has gone.
Will a hazy lens still take good photos?
It can, especially in soft or backlit-free light, and some people like the lower-contrast look. But haze tends to cause flare and washed-out results in bright or contrasty light. Look at sample images taken with that specific lens if the seller can provide them.
What is a yellowed vintage lens?
Some older lenses made with certain types of glass turn yellow or brown over time. The tint affects colour images, but the lens can otherwise be sharp. Some owners reduce the yellowing with prolonged UV exposure. Some of these lenses contain mildly radioactive thoriated glass, so follow general safety guidance: don't disassemble them and don't store them against your body for long periods.