Canon 24-70 f/2.8 L Fungus Cleaning and Aperture Repair
Fungus branching across the glass and a camera that stops recognising the lens at smaller apertures — we fixed both on this Canon 24-70 f/2.8 L for a fixed €250.
Symptoms
- Branch-like fungus filaments visible inside the lens
- Camera stops recognising the lens at higher f-numbers
- Hazy, low-contrast images from the contaminated glass
- Spidery growth spreading between the elements over time
Canon 24-70 fungus cleaning is one of those repairs where timing matters: fungus spreads across the glass, and if the spores are not destroyed it comes back. This case study combined two faults — internal fungus and a damaged aperture — and both were fixed at a fixed price of €250.
The symptoms
A customer contacted us about his EF 24-70mm f/2.8 L USM with two distinct problems. First, the lens showed considerable branch-like ramifications of fungus inside the optics — the spidery filaments you can see when looking through the lens against a light. Second, whenever higher aperture values were set, the camera stopped recognising the lens altogether: fine wide open, dead at smaller apertures.
What causes it
Fungus grows inside lenses stored in humid conditions, feeding on residues on the glass and spreading in characteristic branching patterns. Beyond looking alarming, it degrades contrast and, left long enough, can etch the coatings. Crucially, the visible growth is only half the problem — the spores remain even after the surfaces are cleaned, which is why fungus so often returns a few months after an ordinary cleaning.
The communication failure was unrelated to the fungus: the aperture unit was damaged. It still worked wide open, but when the camera commanded higher f-numbers the lens stopped responding, so the body no longer recognised it.
Can you fix it yourself?
No. The fungus sits on internal elements, so reaching it means disassembling the optical group — and even a perfect surface cleaning at home leaves the spores alive, practically guaranteeing regrowth. The damaged aperture unit can only be replaced with the lens open. The one thing you can usefully do yourself is prevention: store lenses in a dry place and don't leave a contaminated lens sitting next to your other equipment.
How we repair it
Our technicians examined the Canon 24-70mm carefully and confirmed both problems reported by the customer. The lens was disassembled and the damaged aperture replaced first. The optical group was then cleaned of fungus, internally and externally, and reassembled. The final step was the definitive elimination of the spores in our UV chamber.
This UV pass is the step that makes the repair last. If a lens with internal and frontal fungus problems does not go through the UV chamber, the problem can reappear within a few months; the chamber eliminates all the spores definitively, ruling that out completely. The lens left our Canon repair department fungus-free and communicating correctly at every aperture, with the final check included.
Price and turnaround
| Service | Price |
|---|---|
| Aperture replacement + fungus removal with UV treatment, Canon 24-70 f/2.8 L | €250 (fixed) |
| Internal cleaning | Included |
| Final test & calibration | Included |
Typical turnaround is 7 working days. Return shipping is a flat €20 anywhere in the EU.
Ship your lens from anywhere in the EU — diagnosis is free and the repair carries a 6-month warranty. See how it works.
Frequently asked questions
Can lens fungus be removed from a Canon 24-70?
Yes, if it is treated in time. We disassemble the optical group, clean the fungus off the internal and external surfaces, and then treat the lens in a UV chamber to destroy the spores.
Why is UV treatment necessary after fungus cleaning?
Cleaning alone removes the visible growth but not the spores. Without a UV chamber pass, the fungus can reappear within a few months; the UV treatment eliminates the spores definitively.
How much does Canon 24-70 fungus cleaning cost?
In this case study, fungus cleaning with UV treatment plus replacement of the damaged aperture came to a fixed €250, final check included.
Why does my camera not recognise the lens at small apertures?
On this lens the aperture unit was damaged — it worked wide open, but at higher f-numbers the camera lost communication with the lens. Replacing the aperture solved it.
