I just took a photo with manual focus and blurred as much as I could a light, but instead of getting a uniform colour, there are dots, like dust :

enter image description here

Do you know what's causing the darker dots?

  • \$\begingroup\$ I take it this is a 1:1 crop from a small portion of the frame? \$\endgroup\$
    – mattdm
    Aug 29, 2015 at 16:06
  • \$\begingroup\$ @mattdm yes, this is a cropped photo (that has by the way also been zoomed with a lens), why ? \$\endgroup\$ Aug 29, 2015 at 16:14
  • \$\begingroup\$ Because it's a big difference whether this is a pixel-peeping magnified view or the whole scene. \$\endgroup\$
    – mattdm
    Aug 29, 2015 at 16:22
  • \$\begingroup\$ Other information that would be useful: RAW or JPEG from the camera? If RAW, processed with what software? \$\endgroup\$
    – mattdm
    Aug 29, 2015 at 16:26

1 Answer 1


Since you're looking at the pixel level, these artifacts are too small to be dust. It's also unlikely that dust would be outlined sharply when you're using a wide aperture.

I think it's most likely that they are random shot noise combined with demosaicing artifacts, possibly then also smoothed out by denoising.

  • \$\begingroup\$ I don't think it's noise since it's always there (and position varies with lens zoom). \$\endgroup\$ Aug 30, 2015 at 4:51
  • \$\begingroup\$ Can you post an example of that? \$\endgroup\$
    – mattdm
    Aug 30, 2015 at 5:23

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