Sensor Cleaning Guide
Sensor cleaning, for most of us, has always been something of a mystery. One might often feel it necessary to clean one’s sensor, but on the whole, we are all told it isn’t sensible. A ‘don’t-try-this-at-home’ act, if you will. This article serves to dispel some myths about sensor cleaning in the hope that you, the reader, will feel more comfortable about trying it yourself. This article may appear lengthy, but I urge you, if you are attempting to clean your own sensor, this guide will help you to avoid some of the disastrous mistakes I have seen photographers make on their own equipment in the past.
I have been cleaning sensors for Park Cameras for several years now, everything from (the rather impudent) Fuji S2 Pros and EOS D30s right the way through to D3xs and 1DS IIIs. I don’t think it’s a stretch to say that I’ve cleaned hundreds of sensors over this time. From all this I have drawn one solid conclusion: it is difficult to damage a sensor. Provided you take care and treat the sensor like the delicate instrument of precision that it is, you will find it quite hard to damage it. Truthfully, this is because sensor cleaning does not involve the sensor itself, but a thin plate of glass in front of the sensor, called the low-pass filter. This can be compared to the filter placed over an SLR lens, in that it not only serves the function of filtration but also a measure of protection, and this is what you work with when cleaning your camera’s sensor. That said, it is still very delicate and you should always take extreme care, as damage to the sensor can render the camera beyond repair, especially if your camera is a few years old.
The first and foremost point to address is diagnosis. This may seem strange but it could be considered the most important part of the process. Sensors accrue dust at different rates and I’m sure you’ll know if you have a large quantity of dust on your sensor. Dust, however, is not the only substance that appears on sensors. Sand, pollen, flecks of mud and hairs or fibers are also commonplace. Each of these substances require a different method to remove them, and it’s often difficult to tell simply through diagnosis which it is. In order to diagnose whether the sensor requires cleaning your best option is to take a picture of a bright, plain object, e.g. the sky, or a sheet of white paper, at a low aperture. The lower the aperture, the more evident the dirt will become. Choosing which aperture to use for diagnosis depends on the aperture you most commonly shoot with, for example if you normally take shots at high apertures, such as f1.8 or f2.8, then using f8 or f11 will be sufficient to diagnose the state of the sensor. If you often shoot in bright environments at low apertures, such as f7.1 or f11, then f22 is your best bet for diagnosis. The reason for this is that it is possible to over-clean a sensor.
Once you have this test photograph, take it to a computer and zoom in to 100%. To zoom closer into the image than this is unnecessary for the purpose of finding dirt. From here, you will be able to see any grey or black areas on the image that shouldn’t appear normally. These are your specks of dirt. If grey, then it is most likely dust, if black, then something a little more dense. Hairs will appear as a thin black line across the image. As an alternative, or in assistance to test shots, a useful tool is a sensor loupe (7x magnification or greater is recommended). When using a loupe, move your line of sight in and out from the loupe and from side to side. The dirt will often be more visible when you are looking through the loupe from about 4-6 inches away. If you have not looked closely at your sensor before, pay attention and don’t rush. If you are unable to detect dust in a test environment it may well appear at the most inopportune moments.
Once you have established you need to clean your sensor (if you have only a few very faint flecks of dirt it is probably not required), the next step is to access the sensor for cleaning. To do this, take the lens off the camera, put in a fully charged battery, and access the menu option for sensor cleaning (many modern cameras have an automatic and manual option; manual is what we require here) to lock the mirror up and expose the sensor (Nikons generally have the option “mirror lock-up”. If you are unsure, please refer to your camera’s instruction manual).
This is the stage we introduce the tools to perform the clean. The one tool all photographers should have in their kit is the hurricane blower. It is inexpensive and invaluable for the purposes of cleaning a sensor. Before making any contact with the sensor, use the hurricane blower vigorously. You do this by pointing the camera toward the ground so any dirt being removed is assisted by gravity. Now point the hurricane blower up into the sensor chamber, but keeping the nozzle at least one inch from the surface of the sensor, and squeezing it roughly. Show the hurricane blower no mercy and you will be showing your sensor affection. Repeatedly squeeze the hurricane blower at least 10 times, more if there’s plenty of dirt on the sensor. Now you should repeat the diagnosis to see how successful you have been. If dirt has been removed, repeat the clean with the hurricane blower 3, 4 or even 5 times to get as much off as you can. If you have repeated this step 2 or 3 times and have found little or no success, then you should move on to the next steps. If you have removed the worst, there is very little dirt left, or if your sensor is now completely clean, lucky you. You have done the job and can go back to taking pictures. For the rest of us, the next step is to contact clean the sensor. This is when cleaning can be potentially hazardous to the health of your sensor, so remember to be careful.
An important note – and what will be a recurring theme in this guide – is the use of an inappropriate blower. A lens puffer brush is not anywhere near powerful enough to perform the clean, and the brush could potentially scratch the sensor. Some photographers may recommend using compressed air. I do not. Some compressed gas blowers contain chemicals that can harm the coating of the low-pass filter, so keep clear of these. I have known photographers to report success from compressed air canisters, however if you insist on using such a canister, ensure you blast the sensor in short, sharp bursts, not prolonged attacks as this too could damage the sensor’s coatings.
There are various sensor cleaning instruments that allow us to contact clean the sensor. Some are more effective at cleaning certain types of dirt than others. My recommendation for this step is to use a static-charged brush, such as the Visible Dust Arctic Butterfly. This is used by charging the brush (see instructions provided with the unit) and sweeping it across the sensor gently and slowly, just using the very tip of the brush to contact the sensor (the tip is where the charge is stored). It is advisable to place the camera on a work surface at this point so you can hold it securely in place whilst cleaning. I should note here also that any grease on the brush will more-than-likely be transferred to the sensor, so resist the temptation to touch the brush, and don’t place it down without putting the cap back on. Several sweeps with the brush should lift off any dirt that hasn’t rooted itself to the sensor.
There are various brushes on the market designed for this type of cleaning. The Arctic Butterfly is the one I have personally found most effective. It creates the static charge by spinning the brush, and so is efficient in doing so. Many brushes use other methods. In this guide I recommend the Arctic Butterfly, but if you have been recommended something else, do not be afraid to try it. The main point you must remember is that if a brush has not been designed specifically for the purpose of cleaning a digital sensor, DO NOT use it. The risk of damaging your sensor is greatly increased by use of improper tools.
Once again, after cleaning, take another test shot to see if it’s been effective. Repeat this method of cleaning until you feel the dry clean has been utilized to its full effect, i.e. further use is futile or the sensor is completely clean. If your sensor requires further cleaning, a wet clean is the next step. It is important to note, before reading any further, that wet cleaning should be considered the most extreme measure of cleaning the sensor, and as such the most hazardous. It is not complex, but if you are not confident with contacting the sensor by now, I would suggest passing the camera to a professional cleaning service, such as the service Park Cameras provide.
There are many swab and liquid combinations on the market, and most are quite effective. There are surely many I haven’t tried but, from those I have, the most effective and easiest to use I have come across are the Visible Dust Green Swabs and their standard Sensor Clean fluid. As a combination, I have found this to be very good to use, almost never leaving streaks (a characteristic of some of the poorer quality wet clean systems) and removing almost all types of dirt. Some types of dirt, especially lint, will, no matter which system you use, smear the sensor after performing a wet clean. If you do happen to smear the sensor whilst performing the wet clean, do not panic and do not be perturbed. Sometimes this is unavoidable, but can be remedied.
Now for the wet clean itself.
Make sure you have the correct sized swab - this is crucial. There are four commonly used sensor sizes: 4/3rds, APS-C, APS-H and full-frame, which are a magnification of 2x, 1.6x, 1.3x and 1.0x, respectively. If you are not sure which sized swab you will require, please refer to the manufacturer’s technical specification for the model you are cleaning as it will often be listed here. I recommend, before doing anything else, using the hurricane blower on the tip of the swab to remove any dirt or lint that may be there. Next, place small droplets of your chosen fluid across the tip the swab. 2 or 3 droplets should be more than sufficient to cover the whole tip, no matter which swab size you have. Be very careful to make sure you do not over-moisten the swab. Too much fluid on the swab can cause fluid to leak into unseen areas of the sensor chamber and cause the camera irrevocable damage. If accidentally over-moistened, throw the swab away and use another. You may be tempted to touch the tip to check its dampness, but this is ill-advised as grease may be transferred to the sensor by doing so.
To efficiently swab the sensor, hold the swab like a pen, place it on one side of the sensor and move the swab from one side to the other in a single, continuous, slow motion. Do be firm, but do not put too much pressure on the swab; remember, the glass is very thin. Allow the sensor a moment to dry and repeat this, but starting on the other side and moving back across in the other direction. Two sweeps should be enough to remove the vast majority of the dirt. If you can see a smear on the sensor (and this will often be visible to the naked eye provided adequate lighting), a third pass is sensible, just be sure to turn the swab over so that as you move across, whatever may have caused the smear will be unlikely to do so again.
Check the sensor again by taking another test shot. If after the wet clean there is still dirt on the sensor, repeat the process, however this time use a new swab, remembering once again to blow on the tip with the hurricane blower before wetting the swab. At this point you should hopefully have a clean sensor. It is rare, assuming the above steps have been completed properly, that you will still have enough dirt on the sensor to be considered an issue. If you can still see dirt on the test shot repeat this process. Sometimes it can take several swabs before the sensor is thoroughly cleaned. At this stage, if you are not finding success I would strongly recommend passing the camera to a professional sensor cleaning service, where they will be able to clean the sensor to the point that you should be able to maintain the cleanliness of the sensor by using the hurricane blower regularly.
I hope that you have found this guide useful, that you have been successful and are now ready to take your camera out again to photograph the world. Happy sensor cleaning.
If anything in this guide is unclear, or you simply wish for further advise, please call Park Cameras’ Contact Centre on 01444 237070, where someone should be available to help.
*This article is meant for information purposes only. Park Cameras takes no responsibility for any damage that may be incurred to a camera during the course of following this guide.
Hurricane blower should be used first and foremost. Use this regularly to avoid needing deep cleaning often.
Use a static brush and sweep the tip across the sensor.
Use wet swabs with 2 or 3 droplets of cleaning fluid. Blow the tip of the swab before wetting it, and allow time for the sensor to dry before performing another pass.