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enter image description hereI'm using 18-55 canon kit lens on Canon 700D body, the lens works fine with f/3.5 to f/14 , when increase that to f/16 , f/22 a black dot appears on the image, I have tried cleaning lens and body body. Please help.

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  • \$\begingroup\$ What part of the body did you clean? \$\endgroup\$
    – null
    Commented Sep 9, 2016 at 9:36
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    \$\begingroup\$ Could you also please post a sample image? \$\endgroup\$
    – Philip Kendall ♦
    Commented Sep 9, 2016 at 10:03
  • \$\begingroup\$ Sounds like a piece of dust on the sensor. \$\endgroup\$
    – Zenit
    Commented Sep 9, 2016 at 10:18
  • \$\begingroup\$ Sounds just like several existing questions about sensor dust. \$\endgroup\$
    – Michael C
    Commented Sep 9, 2016 at 11:09
  • \$\begingroup\$ photo.stackexchange.com/questions/34718/… \$\endgroup\$
    – Michael C
    Commented Sep 9, 2016 at 11:14

1 Answer 1

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The surface of the image sensor is easily damaged, so it is protected by a glass cover. The cover glass is susceptible to accumulating dust. This happens when we dismount and mount lenses.

Now the lens projects a miniature image of the outside world onto the surface of the image sensor. The image-forming rays must transverse the protective cover glass. Should dust motes be in the path, they shadow the image sensor. The result is a black spot as you describe.

Most of the time, tiny particles cause little harm. They image, but the impairment is so small that it often goes unnoticed. They become more obvious if they are in a uniform area like blue sky etc. They show up strongly when the setting is a tiny aperture. This is because the rays are arriving nearly collimated (nearly straight on) so the dust now shadows most strongly. Consult your camera manual or the web for best method to clean your camera’s sensor.

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  • \$\begingroup\$ I'm not familiar with the Canon 700 but many modern DSLRs have a sensor shake system of one sort or another to try and remove dust. If your camera has this, it's the easiest and safest first thing to try. \$\endgroup\$
    – Joseph Rogers
    Commented Sep 9, 2016 at 15:25
  • \$\begingroup\$ I have already tried cleaning sensor, also camera auto cleans the sensor when power off occurs , also cleaned mirror and lens, its still the same and only happens with low aperture value and starts to show after f/16 \$\endgroup\$
    – Vivek
    Commented Sep 10, 2016 at 12:39
  • \$\begingroup\$ I still think the problem is a foreign object on the cover glass. Inspect the best you can with a magnifier under bright lights. You may need to have the camera professionally cleaned. Or, uses a more aggressive cleaning method. A well washed Tee shirt with a drop of ethyl alcohol. You can use vodka, do not use denatured alcohol. If this stresses you out, send the camera out for cleaning. \$\endgroup\$
    – Alan Marcus
    Commented Sep 10, 2016 at 13:52
  • \$\begingroup\$ @AlanMarcus, I have tried cleaning with lens pen, and cleaning solutions. Should I go to canon service center for cleaning lens ? \$\endgroup\$
    – Vivek
    Commented Sep 12, 2016 at 9:37
  • \$\begingroup\$ Objects on the lens likely do not image. If they are large, they may image as a blob without distinct borders. Black spots are likely objects on the cover glass of the sensor or damaged photo receptors integral to the image sensor. Send both the camera and lens out for service. \$\endgroup\$
    – Alan Marcus
    Commented Sep 12, 2016 at 14:42

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