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I just bought a cheap action-camera and start experimenting with RAW format. The output file has some defective pixels. I know that they can be "removed", but it seems to me that they are too many. I would like to know if this is normal or not. See here a test image (10 seconds exposure). And a second one (automatic exposure, cap on).

The sensor is Sony IMX078.


Thank you.

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  • \$\begingroup\$ When working with long exposures, hot pixels are common \$\endgroup\$
    – Janardan S
    Commented Feb 22, 2017 at 17:43
  • \$\begingroup\$ @Janas You mean the number is increasing with exposure? \$\endgroup\$
    – The Failure by Design
    Commented Feb 22, 2017 at 17:52
  • \$\begingroup\$ What camera are you using? If it's a low-quality camera, then perhaps lots of hot pixels is common. \$\endgroup\$
    – scottbb ♦
    Commented Feb 22, 2017 at 18:08
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    \$\begingroup\$ Those look like hot pixels, not stuck pixels. They're normal for longer exposures on all sensors. There's a process called dark frame removal that is often used automatically in cameras to remove them on long exposures. \$\endgroup\$
    – StephenG - Help Ukraine
    Commented Feb 22, 2017 at 21:17
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    \$\begingroup\$ It's not a defect. It's quite normal - the best DSLRs have these issues in long exposures. \$\endgroup\$
    – StephenG - Help Ukraine
    Commented Feb 23, 2017 at 15:43

1 Answer 1

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With any image sensor you will get some hot pixels and these will be noticeable in long exposures - but easily fixed in post processing. Unfortunately what is a 'normal' amount is very subjective, most sensor manufacturers do mention a percentage of pixels that may or may not work as no manufacturing process is 100% perfect, the more well known manufacturers Sony, Canon etc will have higher quality control than less known or knock off brands.

1) You may have an older / cheaper Sony sensor in your camera that may have a few dodgy pixels 2) You could have a dodgy camera

If you are concerned and the camera is within warranty have a chat with the manufacturer and you may get it replaced or repaired.

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  • \$\begingroup\$ Do you have an opinion on the posted image? Normal, too many? \$\endgroup\$
    – The Failure by Design
    Commented Feb 22, 2017 at 20:20
  • \$\begingroup\$ Well personally, if I didnt pay too much for the camera I would keep an eye on the issue and if it didnt get any worse then I'd live with it. However if I'd paid a reasonable amount I'd personally contact the manufacturer. The old 'you get what you paid for' may apply here :) \$\endgroup\$
    – LMP2016
    Commented Feb 22, 2017 at 20:40
  • \$\begingroup\$ I didn't have high expectations from camera; I was surprised to see so many defective pixels from a Sony sensor. Thank you. \$\endgroup\$
    – The Failure by Design
    Commented Feb 22, 2017 at 20:51
  • \$\begingroup\$ To get a feeling of how many in total there might be, you could find something pure black like a sheet and do a long exposure, this way there will be no distractions in the image and you can better make the call on whether to return the camera or not \$\endgroup\$
    – LMP2016
    Commented Feb 22, 2017 at 20:58

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