Cleaning your Sensor
Are those spots you're seeing, or have the dreaded dust bunnies inhabited your camera?
article applies to all Nikon-based digital SLR bodies (D1, D1h,
D1x, D2h, D2hs, D2x, D2xs, D3, D3s, D3x, D40, D40x, D50, D60, D70, D70s, D80, D90, D100, D200, D300, D300s, D700, D3000, D3100, D5000, D5100, D7000, S1, S2, S3, S5 Pro, 14n, 14nx, and SLR/n). It probably also applies to other DSLRs, as well, but since I don't test them I won't speak to applicability of this information for them.
This page was first put up soon after the D1 came out and professionals started coming to me asking what those black spots they kept seeing in their images were. When Nikon essentially punted on cleaning ("don't touch your sensor"), I wrote the original of this page mocking Nikon with my famous Wendy's Knife cleaning trick (see "Some History" in right column). While my tongue was heavily in cheek with that article, the technique I described worked. Indeed, it worked better than any other solution on the market at the time and was copied without attribution by others, including at least one commercial product.
But a lot has changed over the decade that we've all been shooting Nikon DSLRs. And today things are even more complicated than ever before (and Nikon still tries to disclaim in the US that you can clean your sensor by touch despite selling products that show you how to do just that in Japan).
With the introduction of the D300 (and now also the D3s, D60, D90, D300s, D700, and D3000, D3100, D5000, D5100, D7000), we have yet another variant in cleaning: a camera that purportedly cleans itself. It does a modest job at that, but you'll still have to clean it by hand at some point. Moreover, all of the sensors Nikon uses now have a special tin oxide coating, which some claim can be removed by using the wrong products or techniques. Thus, I've revised this page again. Please read it in its entirety, even though the basics are all boiled down into five simple steps in the middle of the article. And away we go...
It happens to all of us: eventually you'll find an image that, on close inspection, seems to have gotten the freckles (see example, below). No, you don't have bad photosites on your sensor, you have dust on the filter that sits over the sensor.
Don't go trying to eyeball the dust on your sensor filter, though (I'll have more to say on that later in the article now that items like the Sensor Scope are available). Most small spots that show up on your lens are not visible to the naked eye (the largest Nikon photosite is less than 10 microns in size, and several hundred of those could fit on this hyphen: -. Or put another way: if you made your 6mp D70 sensor as big as a football field (100 yards long) each individual photosite would be about an inch square in size. You're just not going to see an individual dust particle with your bare eye (though you may see bigger things, like hairs and pollens). Simple put, it doesn't take a giant glob of dirt to make your camera exhibit the dreaded spots--itsy bitsy and invisible dust particles can be just as annoying as something you can see.
You cant send your camera back to Nikon, Fujifilm, or Kodak every time you get a dust speck on your sensor. If you did, youd pile up quite a freight bill and be without your camera for significant periods of time. And these days, those companies usually charge for the service, as well.
While Nikon Capture (and now Capture NX2) have the ability to use a "dust reference" shot to remove dust from NEFs, this doesn't help you much with most JPEG images (this changed with the D200, which does allow JPEG dust reference photos, but you still have to process the image with Capture or Capture NX2 to take advantage of that). The Capture Dust Off correction is done similar to cloning (i.e. copying neighboring data) but automatically. One problem is that this can sometimes obscure fine detail (cloud threads). Nor does the Dust Off reference photo idea work well in the kinds of environments I shoot in, where the dust accumulation on my sensor changes daily (I'd have to take several reference photos a day and then carefully track them, adding yet more complexity to my already complex workflow). Finally, Nikon's software has an upper limit to the number of dust bunnies it can "erase," and I've encountered plenty of situations where I exceeded those limits. So the dust off reference function in your Nikon DSLR isn't going to help you much. I personally suggest that you avoid using it: it produces too much extra work for too little potential gain.
Eventually youll come around to the decision we all have: that youve got to learn how to clean the sensor yourself.
Oh, one last thing: you're not really cleaning the sensor, you're cleaning the anti-aliasing and IR block filter that sits just above the sensor (on the Kodak DSLRs, this was just an IR block filter).
First, dont be put off by Nikons disclaimers (both Fujifilm and Kodak endorsed user cleaning that touches the sensor if done properly). The Lithium Niobate filter over the Nikon sensors is somewhat difficult to scratch if you use the right tools (on the MHOS Scale of Hardness table that ranges from talc at 0 to diamond at 10, Lithium Niobate is a 5, the same as Apatite, and a bit lower than Orthoclase and Quartz; Fujifilm and Kodak don't identify the material they use [nor does Nikon on the latest cameras], but it seems just as durable). While it's possible to scratch the filter surface, it's also not at all easy to do if you're using the right tools.
Nikon currently uses filters that have a special additional coating on them (Indium Tin Oxide, or ITO for short). This coating is there to help the filter "shed" dust more easily (it essentially blocks some of the static charge that can build up and attract the dust). As with any coating, it is possible to damage it, and when you do so, the filter essentially needs to be replaced. When ITO first became known, it was perceived that an ITO-coated sensor was easier to damage than a non-ITO one. In theory, that's probably true, but in practice it doesn't appear to make any difference. Photographic Solutions dropped their special ITO-only cleaning fluid and now has gone back to Eclipse as their only sensor cleaning solution. Photographic Solutions honors their "no sensor damage" guarantee regardless of whether you clean a non-ITO or ITO filter with Eclipse.
While we're on the subject of coatings, I should mention that if you've had an IR or other filter swapped in place of the regular filter, your cleaning methods may need to vary. Those type of filters are made with different materials and coatings than the antialiasing filter that came with your camera. Thus, they may need different cleaning methods. I can't offer any specific advice here other than to consult the company that provided your filter to see what their cleaning recommendation is.
With that background information out of the way, it's time to look at the tools we use.
What I used to recommend has become a much copied do-it-yourself approach to the tools for cleaning: using Methanol solution with PecPads wrapped around a flexible but stiff improvised holder (my original was a filed down Wendy's knife, but I've used Rubbermaid spatulas and art supply tools from Michael's, as well), advances in available commercial products made the DIY approach no longer necessary. Today, I recommend three products (and you need them all): a common blower bulb, Sensor Swabs (with the correct type of fluid), and the Sensor Brush. Let's look at these in the logical order that you'd use them:
Blower Bulb or in-camera cleaning: Your first line of protection is getting the "loose" dust off the sensor. If your camera has a built-in sensor cleaning function (which vibrates the filter to dislodge dust), then use it regularly (on the Nikon cameras I suggest that you have your camera set to Clean on Shutdown). If your camera doesn't have a built-in shake-it-loose function, then you'll have to blow loose dust out. The most common blower bulb people use is the Giotto Rocket, though there are a wide variety of such blowers available. A good blower can be dislodge casual dust with a few quick puffs of air. A couple of pieces of advice: some blowers have a lubricating material in them that essentially turns into dust. Not good to be using that to blow on the sensor, as you just increase the amount of dust floating around to get attracted back to the sensor. Also, keep your blower bulb clean and well maintained. Throwing it into a dusty drawer and letting it get caked with other materials is going to come back to haunt you. Keep it in an air-free case and clean. I personally use a Giotto Rocket that has been modified by adding a Nikon lens cap to hold its tip precisely and very close to the sensor (but not touching it). This makes the air stream very forceful at the filter due to the close distance to the filter. Again, if you have a camera with a built-in shake dust removal system (D3s, D60, D90, D300, D300s, D700, D5000) you generally don't get any significant benefit from using a blower bulb regularly. Use the camera's built-in system regularly instead.
Sensor Brush: Essentially a brush with extremely fine and soft bristles that have no coatings. You use compressed air (or CO2, or a very strong foot pump) to charge and clean the bristles. You must clean and charge the edge of the brush with air after every pass across the sensor. Light dust (in dry climates) is held onto the sensor by surface tension and static buildup, and what you're trying to do is break that bond and transfer the dust to another surface (the brush). Used correctly, the Sensor Brush works very well on most dust. Indeed, in a dusty, dry environment, it's usually the only cleaning tool I usually need. The biggest issue you face with this product is keeping your brush clean (the original Sensor Brushes come in a protective case; I'm not sure about the latest). The second biggest issue is that it can't remove dust which is welded; but that's why you bought Sensor Swabs, too (see next). Unfortunately, Visible Dust seems to want to push their Arctic Butterfly (see below) and has stepped away from promoting Sensor Brushes. You can still get an 8mm version for US$42, but because it is narrow that means you'll need to do multiple passes on your sensor. Your other alternative is to get the Arctic Butterfly SD800 Pro Kit for US$180, which includes the Arctic Butterfly and a DX and FX sensor sized Sensor Brush. Yes, that's pricey, but it pretty much has all the brushes you'd ever want or need.
Sensor Swabs: These are a simple blade-like swab that you wet with a solution before swiping them across the filter to clean it. The original Sensor Swabs had a fatal flaw--the support mechanism behind the cleaning cloth was not reliable and allowed the edge of the cleaning surface to "break" (bend and reduce pressure, making it not clean well). Moreover, the support mechanism was relatively thick, and if damaged, could produce little plastic pieces that you had to clean up. No more. Photographic Solutions produced a new version that has a full, thin, plastic "blade" behind the cleaning material. It's now possible to maintain even pressure across the edge without it collapsing, even when very wet. The blade itself is a very soft plastic and can't really be forced hard enough to damage a sensor or filter surface. While you can't quite put as much pressure on the edge as with homemade tools, that's a good thing in most ways. The one problem it may create is for some so-called "welded dust" particles (see right column). But this is easily solved by making the Sensor Swab wetter than usual--which might leave streaks that you have to clean up by using another swab). On the plus side versus the home-grown method is that the Sensor Swabs are still made in a clean-room environment and come in sealed packs. Thus, they're ready to go on demand but you won't be having to worry about keeping your cleaning materials clean as you try to wrap them around a home-grown support mechanism. Yes, they're on the pricey side (US$48 for 12), but you won't be using a lot of them because of the other tools you'll be using. Basically, you only use a Sensor Swab when you have a persistent dust particle that isn't removed by blowing, in-camera shake-off, or brush, or you have what I call welded dust. Nikon and Fujifilm users need Type 2 Sensor Swabs, except for the D3, which requires Type 3; Kodak Pro 14n, 14nx, and SLR/n users need Type 3 Sensor Swabs. Note: many Sensor Swab imitations have appeared. Essentially they're all plastic support mechanisms with a lint-free cloth of some sort wrapped over it. While most of those others appear to work fine, I've simply never had a problem with Sensor Swabs, so continue to recommend them.
So here's the full cleaning regimen:
If the above still leaves a stubborn spot, I think I'd let Nikon handle it. Their method of "scrubbing" uses a cleaning tissue wrapped several times around a small wooden stick (and wet with methanol), which allows them to put more pressure on the area being cleaned. But an amateur cleaner isn't likely to be very effective using this technique without putting his or her sensor filter at risk. Given that replacing a sensor filter can be very costly, since it requires dismantling the camera, that's just not something I'd even begin to recommend. So if steps 1 through 5 don't do it for you, send your camera in to a professional for cleaning. Here's the basic recommendations in tabular form:
In Japan, Nikon actually sells a cleaning kit (for camera body, lenses, and sensor). The kit contains training videos (see still image from one, above) as well as cleaning material. This US$80+ kit (!) apparently is only sold in Japan, but it does provide guidance in cleaning a sensor using Nikon-approved methods (and the ones they use in their repair stations).
By the way, itll probably take you a few tries with the Sensor Swabs to get it right. The usual mistakes I see from first-timers are:
Here's a couple of added tips for cleaning:
Recently, we've had two so-called "sensor microscopes" introduced that you place in your lens mount with the camera set to the sensor clean mode. These LED-lighted devices have modest power magnification that allows you to closely examine the sensor surface. The Delkin version is less clear than the Visible Dust version, but neither are exactly great at picking out really small dust. They are, however, reasonably good for checking for streaks after cleaning, for large dust particles and hairs, and for some exotic larger problems (like wet pollens adhering to the sensor surface). Personally, I don't find them worth purchasing: just do a regular, thorough cleaning and don't get anal about examining it! Besides, the longer you leave that shutter open, the more that dust in the air--and there will be dust in your air--will wind its way into the sensor area, and eventually onto the sensor.
There is one unique product that has made it to the market: Dust-Aid cleaning strips. This product is a sticky wicket (literally). You press it gently against the sensor and it pulls off the dust with its slightly sticky compound (supposedly tested to insure it won't leave any residue behind). As such, it's a substitute for the brush type cleaning you normally do.
Finally, the question that sometimes comes up: what do you do if you actually damage your camera during cleaning? First, make sure you've actually damaged it. I've had a number of people show me cameras they thought had damaged filters from cleaning that simply turned out to be either very persistent particles (in one case, a very sticky pollen), or simply had residue left behind due to a botched cleaning. If you live nearby a Nikon repair center, you can ask them to clean the sensor (most of the time they'll charge for that). But if they hand you back the camera and say that you do have a damaged filter, then your choices are these:
My legal counsel wants me to run even longer legal disclaimers than Nikon, but Ill keep it simple: when you work on your own camera, you do so at your own risk. I try to provide accurate, useful information that reflects the way I work, but I cant be held liable for what you do with that information. Use the procedures listed here at your own risk.
My legal counsel wants me to run even longer legal disclaimers than Nikon, but Ill keep it simple: when you work on your own camera, you do so at your own risk. I try to provide accurate, useful information that reflects how I work, but I cant be held liable for what you do with that information. Use the procedures listed here at your own risk.
Why do only some
photos have dust spots?
But don't get too upset, as this is a worst-case test. Some of what you're looking at won't show up in an image. Your goal in a cleaning is to substantially reduce the amount of detail you see in this test. In other words, because of the way Auto Levels works, any imperfection is going to show up, so unless you have an absolutely perfect surface to shoot, Auto Levels will find something to exaggerate.
Orientation: upside-down, but not reversed right to left. If you see a spot on the upper
left corner of your test shot, the dust that caused it is in the lower left corner of the filter of the sensor as you face it from the back of the camera (that would be the right corner from the front of the camera).
Personally, when new commercial tools appear that allow me to retire my impromptu DIY solutions, I go with the commercial tools. In the case of Sensor Swab, that includes a guarantee against sensor damage due to cleaning. So I've taken all my DIY suggestions out of this article and now recommend the commercially available products instead.
I strongly suggest that you retire your Wendy's knives, Rubbermaid utensils, and wood concoctions. I have.
What About Automatic Sensor Cleaning?
If we're talking about the casual dust that I suggest using a blower bulb or Sensor Brush to remove, the systems do a decent enough job.
But if you get pollens, welded dust due to humidity, water drops on the sensor while changing lenses, or a few other types of things that require wet cleaning, the automatic cleaning methods don't work at all. In other words, if your sensor needed a wet cleaning, the current built-in sensor cleaning systems are not an adequate substitute; you'll still need to do a wet cleaning.