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I have a Canon Rebel T6. I'm really newbie and know very little about photography. I think I made and big mistake and accidentally let dust enter the sensor area and the mirror area.

To visualize the dust, I took a picture using f/36.4, ISO 200 and 1/40 sec on an illuminated white surface. The first image has enhanced contrast with GIMP. The second image is without enhanced contrast. You can still see most of the dots. The third is a picture of the sky where you can see some of the dots.

dust with enhanced contrast dust without enhanced contrast sky with specks

Is this dust or dirt going to affect image quality? I bought the camera new a month ago. I don't know what is causing this, but I can also see dirt and fabric on the viewfinder. I thought it was something on the upper part (over the mirror) and cleaned it with magic fiber.

What else can I do?

  • I could remove most (but not all) of the spots in the extra images by windexing my monitor. – rackandboneman Jan 27 at 22:39
  • @rackandboneman sorry, I searched the term "windexing a monitor" but I couldn't find any good info about it. What do you mean by that? – eera5607 Jan 28 at 1:17
  • He means that there's more dust on his computer screen than your sensor. – Peter Taylor Jan 28 at 6:13
  • Oh! I understand. But I counted 64 dots on the sky picture and in my opinion they are very noticeable. – eera5607 Jan 28 at 15:56
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The image with enhanced contrast is not very helpful. However, the unenhanced image does show a significant amount of dust that seems likely to affect images taken with small apertures, as you've noticed. Images taken with larger apertures (something like F5.6, maybe also F8, or wider) should not be significantly affected.

It's also possible for dust on the rear lens element to show up at small apertures. It would be worth checking before messing too much with the sensor.

Try blowing the dust out with a bulb blower or air compressor (some people recommend against using air compressors). If that does not help, you'll likely need to use a wet process. Don't expect to ever get a perfectly clean sensor. Aim for "good enough". See What is the best way to clean the sensor on a interchangeable lens camera (mirrorless or digital SLR)?

Another option is to use dust-removal and flat-field correction software. Some cameras are able to do such processing while generating JPEGs. I do not know if your camera is among them.

  • thank you! I think "real life" pictures look fine in general. But for example, if I take a picture of the sky at f/22 - 36 I can see only the bigger diffuse dots on the image, not the smaller and well defined ones. If I take the same picture at f/11 for example, I don't notice anything. But I'm not an expert. What I wanted to know was if those dots can affect image in a way that I don't notice due to my lack of experience. – eera5607 Jan 27 at 18:42
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This is not at all unusual for f/36 and at enhanced contrast, if you actively used your camera outside and frequently changed lenses for a while.

Apart from diffraction issues, this is another reason why apertures smaller than f/11 are unpopular in modern digital photography.

Contamination that just stops light in certain spots will be almost inconsequential to images shot at wider apertures, unless you are strongly relying on certain effects in the unsharp areas of the picture - eg, if you are working with massive bokeh balls, there is a possibility of the dust showing up in each of them.

There seem to be some translucent contamination spots (oil? dried sugar?), these could indeed cause image quality degradation since they might bend light somewhere it doesn't belong, rather than stop it.

If you actually had a single event where you know an unusual amount of dust got in (eg changing lenses while facing a dust cloud), use the knowledge of what kind of dust that was to find the best way of cleaning it - for example, if you know the dust is abrasive, take special precautions not to scratch the sensor. Sensor cleaning tutorials can be found plenty, if you are not confident doing it have a camera store do it but tell them about the situation you got the dust from.

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