How to Handle Sensor Dust and Lens Marks: A Guide for New Photographers

If you’ve ever zoomed into a photo and noticed mysterious dark spots or smudges that weren’t there in real life, you’ve likely encountered sensor dust or lens marks. Nothing – with the possible exception of a slanted horizon - looks more amateurish than having sensor spots in your photo. These issues are common, even for careful photographers, and they’re far less scary than they first appear. Understanding how to prevent, detect, and resolve them will save you time, frustration, and unnecessary editing later.

Prevention: Reducing Dust Before It Starts

The best way to deal with sensor dust is to prevent it from getting into your camera in the first place. Dust is most likely to enter your camera when changing lenses, especially in dusty, windy, or sandy environments. Try to avoid swapping lenses in places like beaches, deserts, construction areas, or during strong wind.

When you do change lenses, point the camera body downward. Gravity helps prevent dust from falling into the camera’s sensor chamber. Keeping the camera opening exposed for as little time as possible also makes a big difference.

A very effective habit is to have your next lens ready before removing the current one. Loosen the rear lens cap of your new lens ahead of time so you can make the swap quickly and smoothly. The faster the change, the less opportunity dust has to sneak inside.

Whenever you change lenses, blow air into the sensor using a rocket launcher. Be sure to have the sensor facing downward and the blower facing upward. Be careful not to accidentally touch the sensor with the blower. Never use your own breath to blow into the sensor. There’s a good chance you’ll end up with spit on your sensor, making the problem worse.

To minimize any marks on your lens, always have either the lens cap or the lens hood on your lens.

Detection: Finding Sensor Dust and Lens Marks

Each time you go shooting, do the following before you leave your home. Why before you leave your home? Because you may forget later or something amazing (Sasquatch sighting?) may happen when you arrive at your shooting location, and the cleaning will be forgotten.

Dust and marks are often invisible at wide apertures (low f-stops), but they become obvious at narrow apertures (high f-stops). To check for sensor dust, set your camera to aperture priority or manual mode and choose the highest f-stop available on your lens (e.g. f/22).

Next, point the camera at a bright, evenly lit surface like a clear blue sky or a plain white wall. Look through the eyepiece and determine if you can see any markings at all. Look for small dark spots or blotches—these are usually sensor dust.

If you’re planning on using multiple lenses that day, you may want to repeat this process with each of those lenses. Lens marks, such as fingerprints or smudges, tend to appear softer and more spread out, while sensor dust usually looks like sharp, well-defined dots.

Detection: Sensor and/or Lens?

Before cleaning anything, it’s important to determine whether the issue is with the lens or the sensor. One simple method to determine this is to look through your eyepiece and slowly rotate the lens as if you were unscrewing it (without fully removing it). Note that this is not to be confused with zooming in or out with your lens. Do this rotation while looking through the eyepiece. If the dot moves, then the issue is with the lens. If the dot stays constant, then the issue is with the sensor. It’s possible that you have multiple marks, and some move and some do not. Obviously, in this case, you have an issue with both the lens and the sensor.

Resolution: Fixing the Problem (Sensor)

Many modern cameras include a built-in “Sensor Cleaning” function that vibrates the sensor to shake off loose dust. To run this, remove the lens from your camera and point the camera at the ground (which is always the case whenever there’s no lens on your camera).

This feature is usually found in the camera menu and is worth trying first, as it’s safe and easy. Many cameras can create your own “Favourites” menu somewhere in the menu system. If your camera has a sensor cleaning function and a “Favourites” menu, I suggest you put the sensor cleaning menu option into your “Favourites” menu. Then there’s no excuse for not finding it in the menu later when you need it.

If dust remains, a manual air blower—often called a rocket blower—is the next step. A rocket blower is like a turkey baster for photographers. I’ve seen two sizes and recommend not skimping on the size (i.e. buy the bigger one). This will likely cost you ~$20. With the lens removed and the camera pointing downward, use short bursts of air to blow dust off the sensor. Never use compressed air cans, as they can spray propellant onto the sensor.

For stubborn dust that won’t come off with air alone, a dedicated sensor cleaning kit may be necessary. These kits typically include sensor-safe swabs and cleaning fluid designed specifically for camera sensors. Follow instructions carefully and only use products made for your sensor size. Note that the swab size for full-frame cameras is different than the swab-size for APSC cameras (because the sensors are different sizes). Presumably, Micro Four Thirds sensors require a unique swab size as well. To be honest, I have the liquid that comes in a sensor cleaning kit and have never used it because a dry swab has always worked. To be honest again, these swabs are meant to be single-use, but I often reuse them.

The first time you clean your sensor is scary. But it’s really a simple process and takes about 30 seconds. If you’re not comfortable doing this yourself, most camera stores will provide this as a service. If in doubt, take your camera to a store that you trust, and they may demonstrate how to do it. Or ask any of the OCC mentors, and we can walk you through the process.

Resolution: Fixing the Problem (Lens)

If you’ve identified a mark on the lens, it’s useful to determine which piece of glass has the problem. Usually, it’s the lens glass that is farther away from the camera. But don’t forget that it could also be the glass at the end of the lens that is attached to the camera. Since you’re cleaning glass, you may as well clean both ends of the lens.

If you have a filter on your lens (e.g. an ND filter that’s usually used to protect your lens glass), then that will introduce two additional sides of glass (filter front and filter back) that could need to be cleaned.

I use Zeiss lens wipes. They are currently $30 for 200 at Henry’s. There’s nothing overly special about them. They can also be used for cleaning reading glasses. I hope it goes without saying, but never (never, never) use a wipe or cloth of any sort on your sensor.

Sometimes, your cleaning efforts could move marks or even add additional marks. So, you must repeat the high f-stop test to see if the marks have disappeared. You may have to repeat this cycle of check/clean/check/clean several times.

Don’t give in to the temptation of saying you’ll deal with these issues later in editing. The future you will thank the current you if you eliminate the problem before taking your first shot.

Anti-Dust Function

Some cameras have a feature where you can specify if you want the shutter to close whenever you turn off your camera. This is marketed as a way to protect the sensor from dust. On my Sony A7IV, there’s a “Shutter When Pwr OFF” menu option to perform this.

If your camera has this feature, I suggest you do your own research to determine if you want to use it. Many photographers argue, and I tend to agree with them, that it doesn’t make sense to use a fairly fragile shutter to protect a fairly sturdy sensor. If this feature is turned on in my Sony camera, there’s an additional warning to not leave the camera lying around with the lens pointing at the sky. If you do this, then the sun could shine directly on the now-closed shutter, which could lead to warping and other issues.

I do not use this feature.

Final Thoughts

Sensor dust and lens marks are a normal part of photography, not necessarily a sign that you’re doing something wrong. With good habits, regular checks, and the right tools, you can keep your images clean and your camera in great shape. The key is to stay calm, work methodically, and remember that even experienced photographers deal with dust—it’s just part of the craft.