At least a dozen times a week I get emails from prospective lens buyers asking me if there was dust in the lens I am selling.

I always answer that question with a yes and that’s because the vast majority of used lenses will have dust. Just like death and taxes, dust in a used lens is something that should be expected. I have owned and sold OVER 8,000 used lenses for Maxxum film and digital SLRS and Sony digital SLRS and it is extremely rare that I come across a used lens that has no dust. Note: I buy my lenses from sellers all over the country and it makes no difference whether the lens comes from Alaska, Kansas, Washington State, or New York, virtually all used lenses will have dust inside the optics.

Even new lenses will often have dust inside them and it is understandable—the lens is assembled in factories, often by humans. Humans and factories have dust in and on them. Lenses are not made in the same strict dust free environments that computers chips are made in. If the person working on the lens goes outside (for a smoke, a break, lunch, etc.) he will be carrying dust back into work with him (or her).

Recently I purchased a brand new in box Sony Alpha 50mm F1.4 D lens and I saw two specks of dust inside it—and it was a new in box lens. Did I take it back? No. The dust specks have never shown up in any of my shots and most likely I would be exchanging it for another lens with dust in it so why waste my time?

So let me tell you MY FEELINGS about dust.

WHERE DOES IT COME FROM?

Dust is everywhere. Unless you are shooting in outer space (highly unlikely), or in a vacuum (even more unlikely), there is dust where you are shooting.

It’s in your home, in the factory where the lens was assembled, in the store that sold you the lens, in your workspace, on your clothes, in your camera bag, in your hair, and ultimately on your camera equipment.

HOW DID IT GET INSIDE YOUR LENS?

If you are like most people, you are guilty of at least one of the following. Most likely you are guilty of several of these problems:

You do not clean the inside of your camera before you attach a lens. Yeah, I know, your Sony Alpha has the ability to shake off any dust from the chip when you turn the camera off, but where does that dust go? There is no bag to collect the dust that you empty every few days or months. The dust stays inside the lens mount opening where it migrates to the rear of the lens and gets sucked into the lens when you focus or zoom the lens. A good hand squeezed dust remover like a Giotto Rocket can be very helpful in getting the dust out of your camera’s lens mo7unt opening.

There is dust on the inner barrel (that inner tube that extends out when you zoom oir focus) that YOU do not clean off. Every time you zoom or focus, that dust gets inside the lens.

Look at the design of your lens. If it is a zoom, there are at least two areas (above and below the zoom collar) that have seams. Any fixed/non-zoom lens has at least one seam at the focus ring. Dust gets into those seams and then into your lens. Do you ever clean those seams out? I doubt it.

You do not clean off the lens rear mount before attaching the lens to your camera. Well, you can thank yourself for adding dust to your lens since you have just put that off dust inside your camera opening and it will eventually get sucked into your lens. Last I looked, Minolta instructed every owner of a Maxxum DSLR to clean of the lens mount before attaching it to the camera.

You take far too long attaching and removing a lens from your camera. You can blame yourself again since the longer you take, the better chance you have let dust inside your camera and it will get inside your lens.

You remove a rear lens cap and put it in your pocket or inside your camera bag while you are using your lens on the camera. Smart idea--your pants pocket has enough lint and dust inside it to choke a horse and your camera bag is most likely not much cleaner. So, by doing this you get dust on the inside of the lens cap and you then attach that cap (without looking) to the lens. Now you have dust on the rear of the lens and you bring it into your camera the next time you attach that lens because you most likely do not blow off the dust as mentioned above.

You clean your camera (outsides) but do not think about how dirty your clothing is. I constantly see camera users wearing clothing that is a dust mop. If you know your Charles Shultze Peanuts characters, you may recall one named Pigpen who claimed to be carrying the dust from ancient Mesopotamia in the cloud that followed him. People are dust magnets and that dust easily migrates from the camera shooter to the camera and lens.

Then there are other sources that you have less control, over. Dust from the factory, the store, etc. are things outside your control and you can not remove it from the world you shoot in.

HOW SHOULD YOU CHECK A LENS FOR DUST?

I get so many emails from prospective buyers claiming that they do not want the lens I am selling if there is dust inside. They are purists who claim to have no lenses with dust in them. Most claimed they checked every lens they own and there is no dust. Yeah right.

I can almost guarantee that if you have a used lens, it will have dust in it. I can almost guarantee that if your used lens is a zoom, IT WILL have dust in it. If you have checked your lenses for dust, check again, and this time do it the right way.

Clean the front and rear glass carefully (breathe on the lens with hot breath, then clean this off carefully using a CLEAN micro fiber cloth and then a blower like a Giotto Rocket) removing any dust, dirt, fingerprints, etc. from the outside of the glass. Next, take a pen tip and open the lens diaphragm by pushing the aperture tab all the way to the end of its movement. With the diaphragm blades held open with the pen tip, look from front to rear and then from rear to front while tilting the lens towards a bright light source. Do this a couple of times and you will be amazed at the dust you missed just by looking through the front and rear optics with the diaphragm open versus looking through the lens with it closed.

So do you now feel silly for thinking your lens had no dust? You probably paid more for it, thinking it had no dust. I am sure you found some dust in some (if not all) of your lenses.

WHICH LENSES ARE MORE PRONE THAN OTHERS?

The older the lens, the longer it has been exposed to dust and dirt and the more chance it will have visible dust inside.

Zoom lenses are far more prone to dust than fixed lenses and this is easy to understand if you just take a look at the rear of your lens (when it is off camera) and observe what happens when you focus a lens or zoom a lens. Every time you focus a lens you move inner parts of the lens. Every time you zoom a lens you move inner parts of the lens. This movement exposes areas inside the lens where the dust migrates to and ultimately it ends up inside the lens. No lens is perfectly sealed when you zoom and/or focus it and even it they were, those seals will eventually break down and dust will get by them. In fact, if you look at the rear of most lenses, there are huge cavities where dust will get into when you manipulate the inner mechanisms.

Fixed lenses have only one set of mechanicals inside that move. Zoom lenses have two (the focus mechanism and the zoom mechanism).

Push-pull zooms are great vacuum cleaners and great for dust collecting. The push-pull technique used in these lenses works just like the a tire pump and you can actually hear them sucking air when you zoom. That noise you hear also means that lens is now sucking dust from inside your camera opening into the insides of the lens.

Long zooms and macro fixed lenses are often worse than shorter zooms and non-macro fixed lenses. The longer the zoom travel, the more movement of the inside mechanicals and the better the chance for migrating dust getting inside the lens. Macro lenses have long inner barrels and those long travel barrels work similarly to long zoom movement, giving dust a good chance to enter.

WHAT IT MEANS TO YOUR SHOTS?

Usually nothing. Unless the amount of dust specks is great, or unless the particles inside the optics are large. Most, if not all specks will never reproduce.

If you have ever owned a Minolta or Sigma APO lens and have read the Owner’s Manuals for those lenses you will see a note regarding air bubbles inside the lenses. The APO coating technique often leaves some of the optics with air bubbles on them and these bubbles are always a lot larger than any dust speck. Both Minolta and Sigma claim these bubbles (and I have seen APO lenses with air bubbles as large as 1/8”!) will not reproduce so why would a far smaller dust speck?

If you are like most camera users, you are not a professional, and you are most likely NOT blowing up any of your shots larger than a 4’X6”. If you fit that group, most dust specks will never be seen in your shots.

So, rather than wasting your time looking for a lens without dust (a search no easier than one for a 4-leaf clover, or the proverbial needle in a haystack), use that time and effort having fun with your camera and lenses.