Have you ever had this: While shooting out in the middle of nowhere, you notice a phenomena on your photograph in the sky. As it turns out, this phenomena sits on every photo in the exact same spot. From here on you can go the safe route and have your DSLR cleaned. But what if there is no time, or what if there is no place to have it serviced nearby and you did not bring any cleaning gear? In this post I will show how to clean your DSLR sensor using just a cotton swab.
Even though I think it is VERY difficult to damage your camera using a cotton swab, I must warn you that all things you do based on the information in this post are at your own risk. If you are not comfortable with steps described here, just have your camera serviced at a Canon service point.
That said, I think you do have a chance to damage your camera if you manage to have the mirror collide with a cotton swab. I do not think you have to worry about the sensor itself: You will not be touching the actual sensor, but merely the filter that sits in front of the sensor. And that filter is a glass surface. So go out with a cotton swab, and try to scratch a window of your house; I think you will not succeed, just as you will not manage to scratch your sensor. There is one important exception to the rule though: If you manage to have a grain of sand on the swab or your sensor, then you obviously will risk scratching it while cleaning. I personally have never seen sand clinging to a sensor though, it must be VERY fine grained in order to be able to, but I just want to make you aware that something like this could potentially happen.
How do you know if your sensor is dirty
For some reasons sensors get dirty. Sometimes they stay clean for months, then all of a sudden it is like someone sneezed directly onto it. I have an example here of a very dirty sensor which I noticed during a macro shoot. The top picture is a shot with flash (so the background is dark) which I overexposed for the purpose of showing dirt, the bottom picture is a shot without flash, which I darkened for the same reason:
As you can see, the arrows clearly show smudges (and even a hair like shape) on the pictures that are in the exact same position for both shots. This is a clear indicator that the sensor is indeed dirty.
The next step is to make a photograph with this camera to clearly show if your sensor is indeed dirty…
Making a photograph that is optimized to show sensor dirt
So how to make a photograph that will clearly show if there is any dirt on the sensor? This is a little different from ordinary photography, as you aim to photograph something stationary on the sensor, and not wanting to photograph anything else (yet you need light onto the sensor). The recipe for creating these photos:
- Use a moderate zoom lens in the 100mm range, or at least above 50mm. For a zoom lens, zoom it over 50mm;
- Find a white piece of paper to take your shot (we want to illuminate the sensor as even as possible);
- Set your lens to manual focus, and turn it complete out of focus from the piece of paper (focus will not matter for dirt ON the sensor, but it will help to hide any spots on the lens/paper);
- Set your exposure mode to Av, ISO to 100 and set the aperture to a very narrow – at least to f/22 (important!).
Now take your test picture. Do not worry if the camera uses 1/2 second as exposure time – that is even better! Motion blur will make sure even more that anything the lens sees will blur out…. And as we are only interested in seeing the dirt on the sensor, motion blur will actually help here.
If you want to show the dirt even better, modify the picture using your imaging software:
- Max out on contrast;
- Underexpose by around 1,5 stop;
- Turn up the black level (if your software features this).
When I looked at my test shot, I got a picture like this:
Now THAT is a dirty sensor! Up next: How to clean it using only a cotton swab…
Cleaning your sensor
So now you have discovered that your sensor is actually dirty. The next step of course will be how to clean it. Once again, if you feel uncomfortable doing the steps described below, DO NOT proceed but have your camera serviced instead. For those willing to continue, read on…
The first thing to do is unmount any lenses from the camera. When you look inside, you are now looking straight into the mirror. We’ll need to lock up that mirror to show the sensor behind it, and to be able to clean it. You could select a 30 second shot, but that is risky as you need to be out of your camera within 30 seconds (or pay for the consequences of your mirror launching itself into your cotton swab). Instead, it is better to use the software inside your camera to select “clean manually”. This option will lock the mirror in the “up” position, and then freeze the camera. Only turning the camera off will release the mirror again (so MAKE SURE your batteries are charged!!):
Once you managed to get the mirror to lock into the “up” position you are now looking straight at your sensor:
You can try to rotate your camera in the light and maybe you’re able to spot the sensor dirt as the reflection runs across the sensor. Most of the time though, the bare eye can hardly see the dirt.
You can now try to clean the sensor using a dry lint-free wipe. Make sure the wipe is clean before you start! You can also use a cotton swab, but be VERY careful when you do: Cotton swabs can leave fibers behind that can jam the mechanics of your camera. Professional camera repair shops will never use swabs for that reason. I myself do use cotton swabs, but again, be very carefull that a swab does not loose a fiber when cleaning. I always clean the sensor using a motion like this:
I start off with pushing the swab over the surface in lanes from left to right, and I rotate the swab a tiny bit after each lane (to get a “clean spot” on the swab for the next lane). This will push all dirt to the right side of the sensor. Finally, I swab the right side from top to bottom to take out any of the accumulated dirt, and I twist the swab as I finish to make sure the dirt will sit on the swab.
This basically completes the “dry cleaning” of the sensor, and this just might be enough to remove the dirt. After this, just repeat the test shot and see if the sensor comes out clean this time. If not, repeat or do a “wet cleaning” described in the next section.
If dry cleaning fails: Wet cleaning
So what if dry cleaning does will not work? I have an example here, where a sensor contained pieces of dirt that were oily:
The way I perform wet cleaning without any tools, is to breath onto the swab to make it moist. If that does not help, I will breath straight into the camera onto the sensor until it is nice and evenly covered and looks like milk glass. Then I repeat the proces, swabbing left to right in lanes and finishing up with a swab from top to bottom in the right corner just like in the dry cleaning process.
This approach has always worked for me. Breathing on the sensor has not left any stains on the sensor ever, and I am happy to be able to clean my sensor without any real tooling at hand.
As soon as cleaning the sensor using my “wet cleaning” technique would not work, I’d probably have it cleaned professionally or I’d start to look for a wet cleaning tool. So far I have been able to do without; as soon as your test shot reveals an evenly grey image, you’re done!