How to Spot Dust on Your DSLR Sensor

Are you getting frustrated with seeing small dark spots in your images that seem to show up in every image? If you see them consistently in the same location (the size and darkness of the spots can vary depending on aperture), you are most likely dealing with dust particles on your camera’s sensor. In this short article, I will show you a quick and easy way to identify sensor dust when shooting outdoors.

What is sensor dust?

If you own a DSLR, you will at some point have to deal with sensor dust, whether you like it or not. Dust is a normal fact of life and it is all around us, even at our homes that we try to keep clean at all times. The dust lands on both the lens and the camera body and due to the “breathing” mechanism of the lens while zooming in/out and focusing, the small dust particles end up getting sucked into the camera body. All lenses breathe one way or another or else the internal elements would not be able to move for autofocus and zoom functions. If you use more than one lens, the dust might be able to get into the camera body during the process of changing lenses.

Once the dust is in the camera body, it will either fall on the bottom of the camera or move around until it lands somewhere. Some dust particles land on the mirror inside the camera and others might end up getting stuck on the camera sensor. So, as you can see, there are three main areas where dust might settle in:

  1. The camera mirror – when dust ends up being on the camera mirror, you will not see it in your images, but you will see dust particles when you look through the viewfinder. This one is just annoying and it can be easily cleaned either with a small brush or a blower like Giotto’s Rocket Blower.
  2. The lens exterior, front and/or its back element – while very small dust particles will not affect image quality, the larger ones and dirt/grease will decrease contrast and might even possibly degrade image quality. Always make sure that both the front and the rear elements are clean and dust/dirt free.
  3. The camera sensor – the worst case scenario, because the dust particles will show up in every image, especially when stopped down to small apertures like f/10. Cleaning the camera sensor is not easy and the process requires special tools that need to be used with extreme care.

The first one is not a big deal – if you see some dust inside the viewfinder but you do not see it in your images, do not worry about it too much and only clean the mirror if it is too annoying for you. The second and third are the ones that can spoil your images and have a negative effect on affect image quality. Let’s talk about lens dirt first.

Dust/Dirt on the lens

How does dust, dirt and grease affect the image that comes out of your camera? Dust and dirt on the front element will rarely be visible, unless there is too much of it. Even then, you will not actually see any dots in your image, but rather will notice that your images are a little “hazy” or “cloudy”, which photographers simply call “decreased contrast”. If only a part of the front element is affected, for example an oily finger touched the front element, then you will see something like this:

Grease on front of the lens

Note the white area inside the circle – that’s how oil/grease would affect the image. In many cases, you might see a color shift in addition to decreased contrast.

What about dust on the rear element? Take a look at the following image:

Dust on the rear lens element

See that large dark spot on the top of the frame? When I took the shot and looked at the viewfinder, I immediately knew that the rear element of the lens had a large dust spec on it, because neither the dust on the front of the lens, nor on the camera sensor looks anything like the above. I changed lenses in a very dusty and windy area (not a good thing to do) and something large ended up landing on the rear lens element before I mounted it on the camera. The result is a large dark circle in the frame!

Dust on the camera sensor

What about dust on the camera sensor? Dust on the camera sensor can be quickly identified from the following:

  1. The size and visibility of the dust particles will change as you change lens aperture. At maximum apertures on fast lenses such as Nikon 50mm f/1.4G, you might not even notice the dust particles in your images, which does not mean that they are not there. They will only be visible at smaller apertures such as f/4.0-f/5.6 and higher. As you increase aperture to a larger number, the dust will appear darker and more pronounced and the size of it will also get a little smaller.
  2. Dust particles will always appear in the same spots.
  3. Sensor dust can never be seen through the viewfinder, it only shows up in images. Even then, you might need to zoom in to 100% to see it. Larger dust particles and hair can be visible right away without having to zoom in (see example image below).

Here is an example of sensor dust:

Sensor Dust

Those three sensor dust specks ended up being on my sensor after a long day of driving through a very dusty area. As you can see, the dots are quite obvious and are much smaller than the earlier example of dust on the rear lens element. I used a small aperture of f/10 for this shot to get the bird in perfect focus, so the dust specks showed up right away.

How to see sensor dust

If your camera has dust on its sensor, you can quickly spot it by doing the following:

  1. Set your camera on Aperture Priority Mode.
  2. Set your metering mode to Matrix/Evaluative Metering.
  3. Set your camera ISO to the lowest number such as ISO 100 or 200.
  4. Turn off Auto ISO.
  5. Turn off autofocus and set your lens on manual focus.
  6. Set your aperture to the largest number available for your lens by rotating the camera dial. For example, the minimum aperture on the Nikon 50mm f/1.4G is f/16, so if I were shooting with this lens, I would set my aperture to f/16.
  7. If you are outside, point your camera up at the clear blue sky and take a picture. If you are indoors, find plain white paper, zoom in all the way so that the paper fits the whole frame, then make sure that the lens is completely out of focus and take a picture. If you are in front of a computer, open up a text editor such as Notepad, maximize it to the screen and then get as close to the monitor as possible so that only the white color is visible in the frame. Make sure that your focus is way off (completely out of focus) – that way only dust particles will be visible.
  8. Zoom in on the image (rear camera LCD), scroll from left to right and top to bottom all over the image and see if you can find any dark spots.
  9. If you cannot see any, your sensor is clean. If you see dark spots like in the above example, then your sensor has dust on it.

Here is a shot of the sky that I took at f/16 after seeing dust in my image:

Sensor Dust Test

The large dark circle is dust on the rear element of the lens, while the dots and hair are both on the camera sensor. As you can probably tell, I had to do some cleaning of the sensor after I saw the above. I obviously did not do it on location, but in a dust-free environment as soon as I got back home.

I will go over the process of cleaning camera lenses, DSLR mirror and sensor in a separate article very soon, so stay tuned!

Comments

  1. 1
    ) Gyula
    July 31, 2010 at 4:46 am

    Another useful article…thanks for sharing it with us!

    • August 18, 2010 at 1:03 pm

      You are most welcome Gyula!

    • 31
      ) shekhar
      January 15, 2013 at 11:30 am

      i got my dslr sensor cleant at mata cameras and my lens had fungus also , now my complete set is perfect. this i guess is very good service in bangalore at mata cameras. contact details 9035871324. this service centre is at sp road bangalore

  2. 2
    ) Pasquier
    August 1, 2010 at 3:06 am

    Hi Nasim
    this will be avery useful series – cleaning dust from the sensor is not a fun thing to do – keen to see what tips you offer. Best, P:)

    • August 18, 2010 at 1:04 pm

      Pasquier, yes, except I have not had time lately to write a guide on cleaning sensors yet ;-) Too much gear to test, too little time!

  3. August 1, 2010 at 4:58 am

    I’m curious as to why the aperture would matter to sensor dust. Why would it be clearer at a smaller aperture if it’s on the sensor? I would think the further the distance, the more the aperture would matter (like the rear lens element for example), and that it would make very little difference on the sensor. Are the filters in front of the CCD that thick that aperture would play that big a role in sharpness? Just pondering how things work… :-)

    • 4
      ) Rodrigo
      August 1, 2010 at 9:30 am

      Hey Aaron maybe this can be the reason,

      You need light to hit on the sensor to be able to see the different colors, no light means black. You are already eliminating the possible blacks/shades by picking a nice plain, lighter, color background. So the last piece of the puzzle is a thin beam of light (minimum aperture) that can illuminate the sensor without being too bright/strong so that the glare could hide the “dark” specks. If I remember correctly the larger the aperture more light gets in, the harder it is to control because it will more easily bounce in all the lens surfaces.

      But maybe I’m wrong.

      Cheers,

      • August 1, 2010 at 9:44 am

        Rodrigo, you might be on to something! I did a little more research after reading your comment and thinking about it. I found this: http://www.dmcphoto.com/Articles/SensorBrushes/ Quoting a few sentences:

        “The surface being photographed should be no more than a few feet away. The idea is to make the item being photographed extremely out of focus so the only details in the final image will be dust spots and not features of the item being photographed. The small aperture makes the light rays between the back of the lens and image sensor parallel to one another and perpendicular to the glass sensor cover. That causes any dust on the glass cover to cast more distinct shadows on the image sensor. The long focal length makes it possible to assure the image is completely out of focus at the lens’s smallest aperture, which would be impossible with a very wide angle lens.”

        • August 18, 2010 at 1:11 pm

          Oops, looks like you already found the answer ;-)

    • August 18, 2010 at 1:11 pm

      Aaron, sorry for a late response!

      The primary reason is the shape and direction of light – when you use a large aperture, the light spreads from the aperture all over the place, hitting dust particles on the sensor filter from different angles. When you use a small aperture, the light is perpendicular to the sensor and the dust spec is hit from a much narrower angle, which then exposes dust particles more by casting hard shadows vs soft.

      Hope this makes sense :)

  4. 6
    ) Vivek
    August 7, 2010 at 2:13 am

    excellent.. need to check out mine today itself!

  5. 7
    ) Mymy
    August 13, 2010 at 12:49 pm

    Nice article.Waiting for your “how to clean camera lenses”, i will defiinitely stay tune….

    • August 18, 2010 at 1:13 pm

      Mymy, sorry, but I have not had time to write the article yet. It is still in my “to-do” list.

  6. 13
    ) Vivek
    October 10, 2010 at 10:25 pm

    Hi Nasim,

    I have got fungi on my 18-55 nikon kit lens.. Is ther any way I can clean it by myself ? Think its on the outer side of the lens.

    Thanks,
    VIvek.

    • October 22, 2010 at 1:17 am

      Vivek, when you say that it is on the outer side of the lens, can you be more specific? Is it just on the front element or can you actually see it inside? If it is the latter, then you will need to send your lens to Nikon for repair.

  7. 15
    ) Nikhil
    March 28, 2011 at 7:39 pm

    Hi,

    I got a Nikon D7K. When I photographed blue sky, i noticed one darker patch on it. I have done the test detailed here and found that a dark spot is there on the top left corner. But what I am confused is that, the same dark spot is visible on both LIVE VIEW and VIEW FINDER. So I changed the lens and verified, but still the dark spot is there. I checked my lens and they are clean and spotless. Can you please help me out to figure whether it is a sensor dust or some other problem

    Thanks
    Nikhil

    • 16
      ) Rahul
      April 25, 2011 at 11:36 am

      hi,

      If the spot remains in both the viewfinder and in live view, it is most like the lens. The spot could be somewhere other than the front element. Have you tried zooming at different focal lengths , the optics might dilute the anomaly at different positions of the lens elements.
      Try another lens if you can, as well.

      • 17
        ) Nikhil
        April 25, 2011 at 7:52 pm

        Hi Rahul,

        Thank you for your reply. I tried with different lens also. But the spot was still there. So i took it to the service center and the told me that it was sensor dust. I was surprised because, it was only a month I bought the camera and also I rarely change lens during any travel. They cleaned it in 5 mins and now everything is fine :)

        Thanks
        Nikhil

        • 18
          ) Rahul
          April 26, 2011 at 8:40 am

          That’s good, but it doesn’t explain why the spot was visible in the viewfinder as well.

          • 19
            ) Nikhil
            April 26, 2011 at 9:37 am

            I am currently in Shanghai and bought the camera from here. I gave it to the service center here. I asked them whether it was a sensor dust or something else. The service engineer there speaks only little English and he did not understand my question properly. After making certain desperate attempts in making him understand my question , I retired :) Anyway service was good and fine, and it was a 5 mins job.

        • 30
          ) Rakshnna
          January 5, 2013 at 10:50 am

          did it cost you anything? Because I just inquired and they told me it would cost me 800 and odd :P They said they might want to replace it! Scary!

      • 36
        ) mo
        June 4, 2013 at 5:17 pm

        Hi! First of all thank you very much for these quite understable explanations. I was suspicious about dust on my camera sensor because of some white spots on some phtos, so I followed the rules and did the test with the withe paper twice, one for each lens. I found 14 (fourteen!!) dust spots and also fine shades here and there.
        I also noticed a little spot when I look through the viewfinder, that spot is not on any lens because I looked through it without the lens and the small spot is there near a focal point mark. I bought my camera for about 5 months and I am very careful with it, also when changing lenses which I don’t do too often. What do you suggest, I mean, what is your advice? I’m a bit afraid of touching the sensor as well I don’t think I can afford take it to a technician. Thank you very much!

  8. 20
    ) veronica
    August 30, 2011 at 8:43 am

    I have a question.
    I’m thinking of buying a used lens. It says that there’s quite a bit of dust in the second element. What it that mean? Does it affect the quality of the photo? I have been looking all over the internet and I can’t find anything about it! Unless there’s a different name for it! Also, would a used lens affect my new camera body? I had always used new lens, so maybe it’s a silly question but the dust ( which I don’t know where actually is) could affect my camera?
    Thanks for your help! I found your posts very very helpful!

  9. 21
    ) Eduardo
    November 4, 2011 at 6:25 am

    Hi Nasim, I wonder if you could help me. I can see a little spot of dust through the viewfinder of my D5000. I believed it was in the lens but I changed it and nothing changed. It is not in the sensor since it is not seen on my pictures. Is it on the mirror sistem? I tried to blow some air using an AA1910 Giotto’s rocket air blower but the dust spot remains there. What can I do to remove it? Despite not spoiling my pictures it is bothering me.

    • November 13, 2011 at 11:39 pm

      Eduardo, the dust is either on the mirror, or right above the mirror on glass surface. Try to use your blower on both and hopefully it will be removed.

  10. 23
    ) Peter Creta
    March 15, 2012 at 6:05 pm

    hi nasim,
    a week ago i bought the point and shoot nikon s9100 with 18x zoom. i found a rear element dust on my photos when i zoom. the lens is not removable to clean it by myself . do you think that a technical could open it and clean it?

  11. 24
    ) PRADEEP SWAIN
    August 16, 2012 at 6:39 am

    Dear sir, I have been following different authors from different parts of the globe, who are really really very much talented in Photography profession. But when it comes to you I can say that if anything top award like Novel prize is there in photography, it will go to you. You are the perfect person and I salute your knowledge.

    The most humble part is your attitude to share your knowledge. I think no other author shares this much of knowledge and experience you are sharing.

    I am from India. Last year I purchased a used Nikon D70s camera. But I didn’t know the use of camera. But learning from your blog I am learning lots of things. The simple English language is helping a lot to
    understand your articles. I hope one day I will be able to capture a good photo which will truly satisfy me.

    You are an encyclopedia of photography.
    Thanks and regards,
    PRADEEP SWAIN.
    VIM-278, Sailashree Vihar, Bhubaneswar,
    State- Odisha, Pin Code- 751021
    Country- India

  12. 25
    ) Mike P
    September 14, 2012 at 3:11 pm

    I just tried to clean my D40 with this method and unfortunately, there are still significant dust particles after 4 attempts. I am nervous to do my D700, but I do see a lot of dust on its sensor as well (using the testing method). I may just leave it there!

  13. 26
    ) BOHDAN MAZHAR
    November 9, 2012 at 2:30 pm

    Молодец, спасибо. Мы с женой многому у тебя научились.

  14. 27
    ) shiva
    November 30, 2012 at 11:32 pm

    While checking your test photo in a computer screen,. please clean and double check the dust in your computer moniter screen. you may be fooled by the dust which is already there in your computer screen..

  15. December 15, 2012 at 7:59 am

    Oh my god! I am seeing so many spots on my sensor.. In the first attempt, I didnt believe there could be so many. But when 2nd and 3rd attempts on different white surfaces also showed same spots at same places, I had to believe it.. :( Thanks for opening my eyes!

  16. 29
    ) Rakshnna
    January 5, 2013 at 10:47 am

    This is exactly what has happened in my case. Thanks for the help. I would like to know where your next article is. The one where you said you will be illustrating about cleaning the sensor, mirror etc.
    Please reply.

  17. 32
    ) Carlo
    January 21, 2013 at 4:18 am

    Wow! I learned so much from your website.
    I got a nikon d3200 last december 2012 and after using it in a dusty environment I found my sensor full of dust. I bought an Eclipse sensor swab and cleaner, sad to say its the only cleaner here in the Philippines.
    I cleaned it the way you taught in your video. And my sensor’s already clean.
    I just want to know how do I know that my sensor was damaged by using the Eclipse cleaner?
    Thank you very much!

  18. 33
    ) ens
    February 9, 2013 at 10:16 am

    what about the mirror(the part where the light hit 1st) and the focusing screen? :\
    i noticed some bluish-marks at certain angle on the mirror…

  19. 34
    ) Dwayne
    February 25, 2013 at 10:02 am

    Thanks! I can see just how dirty my sensor is. Great website for educating photographers of all walks.

  20. March 11, 2013 at 11:38 pm

    This is a wonderful article. I’m dealing with heavy dust issues on my sensor (and self-cleaning has appeared to make it worse) that need to be taken care of.

  21. 37
    ) mo
    June 4, 2013 at 5:19 pm

    Hi! First of all thank you very much for these quite understable explanations. I was suspicious about dust on my camera sensor because of some white spots on some phtos, so I followed the rules and did the test with the withe paper twice, one for each lens. I found 14 (fourteen!!) dust spots and also fine shades here and there.
    I also noticed a little spot when I look through the viewfinder, that spot is not on any lens because I looked through it without the lens and the small spot is there near a focal point mark. I bought my camera for about 5 months and I am very careful with it, also when changing lenses which I don’t do too often. What do you suggest, I mean, what is your advice? I’m a bit afraid of touching the sensor as well I don’t think I can afford take it to a technician. Thank you very much!
    Canon 1100D

  22. December 2, 2013 at 10:11 am

    Hi (:

    Is “Dust off reference” effect the resolution of the shot?

    I’m shots landscape and macro, And sadly I’m using the Nikon D600 that have dust on the sensor every 300-500 shots

    I hope you can help me please about the resolution question?

    Have a great day (:

  23. 39
    ) krishnakumar nair
    December 4, 2013 at 11:30 pm

    very nice article. found it extremely useful. I clicked pictures of my laptop screen after opening NOTEPAD, opened the pictures in PICASA, clicked on I AM LUCKY for better contrast. It is better to click two pictures and toggle between the two. The dust on the sensor looks sharp and is stationary. Also click at higher apertures( like f8,f3.5,f1.8) and observe that the spots just blur and fade away, hence, we do not observe these at the apertures that we normally shoot at.

    • 40
      ) Guy
      December 5, 2013 at 2:41 pm

      But most of the time (in landscape) I’m using f/22…

  24. 41
    ) Pol
    January 17, 2014 at 12:20 am

    This article was so useful, thank you ever so much! I had a spot of dust on the rear element of my telephoto lens, and in 2 seconds using google I found your image explaining what was causing the problem with my image. I will certainly bookmark it for future use.

  25. 42
    ) Rohit
    February 9, 2014 at 8:58 pm

    HI , have got a problem in my camera when ever i click a photograph there is a line coming on top of my pic every time plz help

  26. 43
    ) Munaf
    August 28, 2014 at 11:05 pm

    Great article Nassim.

    I think I can spot 3 specks of dust that match those for sensors using your method (I used a white wall lit by a slightly yellowish light). 2 are faint and blurry, rather like those in your example. 1 is much darker, and more distinct, does this mean that it is a darker spot of dust? I’m hoping it’s not any damage.

    Looking forward to your cleaning article, thanks!

Leave a Comment