Gene Walls

Gene Walls

Williamsport, United States

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What Is "Lens Fungus"? Can It Really Affect My Camera Gear?

I just discovered that a tiny amount of fungus is growing inside my Canon 100mm Macro lens! I should have found it sooner, because I am quite familiar with this insidious problem. The growth in my lens was just located as I was editing this tutorial, when I decided to take my own advice and check all of my “glass”. I am well aware that I must get my lens into the shop as soon as possible. The fungus will never just go away on its own. Fortunately, I found the growth at a very early stage, so I’m pretty sure that the contamination can be removed. This terrible condition can happen to anyone’s lenses, even to an avid lens fanatic like me. I’m hoping that people will read this article and possibly find the problem before it can cause permanent damage to their own photography gear. This is serious stuff!

Lens fungus contamination is caused by a combination of moisture and dust (containing fungus spores) that can get inside your lens’s interior elements. Some dust gets inside every lens, especially if it’s a lens that isn’t fully “weather sealed” like the very expensive professional models. The dust specks are usually not a problem, by themselves. However, add a little moisture, and very bad things can happen!


This is one of the worst cases of lens fungus I have ever seen

When moisture gets inside your lens, either because of direct moisture exposure (like rain) or simply because of very high humidity in your local climate, fungus can begin to grow. Some lenses that I have examined, that came from very humid “tropical” areas like Hawaii and Florida, have had the worst cases of fungus growth that I have found. Not all of them, of course, but there is a noticeably higher percentage of lenses from these very damp areas that are affected. Very few lenses from arid climates suffer from this problem.

An unexpected situation can be created when a lens is exposed to extreme cold and then brought into a nice warm environment, like your own home sweet home.  The normal ambient atmospheric moisture inside a cold lens can condense into liquid water droplets or “fog” on the chilled interior surfaces in the lens. This happens especially when the lens is allowed to warm up very quickly. The best way to control this is to leave the chilly lens in its closed protective case and allow it warm back up very slowly, whenever it has been brought inside after prolonged exposure to sub-freezing conditions.

Overall, one of the best ways to control moisture is to keep small packets of “Silica Gel” desiccant inside the case with each lens. (Most new lenses come with a Silica Gel packet inside the box. Keep it and use it!)

When moisture does find its way inside your lens, it provides a rich medium for the fungus spores that are often mixed in with dust particles (remember, the dust was probably already inside your lens). The fungus then begins to grow and it multiplies in a moist environment. If this problem is recognized quickly, a professional lens technician can clean it. However, if it is allowed to multiply over time, it causes permanent “etching” in the lens coatings. This condition is not usually reversible and it can permanently affect the image quality of the lens.

Fungus Behind the Front Lens Element – This problem was solved and the lens was saved

The preferable solution is always PREVENTION.  However, if you find the signs of fungus when you look through your lens, have it inspected by a professional at as soon as possible. Hopefully, you can have it cleaned before the problem becomes much more serious. If left untreated, fungus will continue to grow and grow until the lens becomes unusable.

Please note that a single infected lens can be like the proverbial “bad apple”. Fungus can actually spread to all of the other lenses in your camera bag! Don’t let this happen to your gear. Inspect you lenses regularly and have the problem solved immediately if you find any sign of “hazing” or water spots inside your lenses.

It is very easy to inspect you SLR lens. Simply dismount the lens from the camera, remove both lens caps and any mounted filters. Be sure to inspect the lens very carefully from both ends. Look straight through the lens, directly into a bright light source. It could be a bright sky or a light bulb. You will probably see some specks of dust in there, that’s OK, it is quite normal and usually has no noticeable effect on the lenses optical performance. However, if you see “water spots” or any haziness, or worse, actual fungal growth, it’s time to isolate this lens from the rest of your gear and get it to a repair shop as quickly as possible.

This 50mm Macro Lens Couldn’t Be Repaired, It Was A Total Loss

In really bad cases, you might find actual fungus growing inside the lens. Fungus can look like tiny spider web patterns or odd white splotches on the glass elements inside the lens. At its worst, the fungus will have small filaments growing beyond the glass surfaces, like little “whiskers” (like the lens that is pictured at the top of this page). Obviously, this would have a serious negative effect on the lens’s performance, eventually causing very fuzzy images and major color shifts. The lens cannot be saved at this point.

Do yourself a huge favor …pull out your lenses and take a quick look inside each of them right away. Do this inspection procedure at least once every season. It takes so little time to do, but it could save you the cost of having to replace your precious lens (or lenses)!

Your lenses are probably just fine, but wouldn’t it be better to know for sure?

Let’s take care of the tools of our trade …they could make us or brake us, if we’re not careful.

Any reports about your own lens inspection findings, or any questions that you may have, can be left as comments to this journal. All comments and questions are welcomed.

Please note that this tutorial is fully copyright protected work by Gene Walls (AKA ProfAudio)

© 2010 Gene Walls

All copyright and reproduction rights are retained by the author. None of this text and / or any of the photos may not be copied, reproduced or altered by any way without the express written permission of the author. This includes my images AND THE 100% ORIGINAL TEXT. An invisible copyright watermark is embedded to guarantee successful prosecution, in the event of any violation.

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