I discovered red/blue/white pixels on my night photographs tonight. Trying to confirm this, I took a black image with the lens on and indeed I saw a whole lot of them (I didn't count them but at least a good fifty on the whole picture).

I'm not exactly sure if they are hot pixels, stuck pixels or anything else.

I quickly gave a check to my last exported JPEG files (I get RAW out of the camera) and couldn't find anything. After a quick search, I've seen that Lightroom is caring about those pixels after RAW conversion.

I've read that, with Canon DSLRs, there is a software process that could take care of that directly on my camera. I don't know if I can use it without getting things even more messy.

My question is: Considering my crazy pixels are not visible on my pictures, should I get too emotional about them? My camera is under warranty but is it really worth it to return it to Canon? If it's only to receive it back 1 month later after Canon just used the very same menu to map out the pixels, it's a bit ridiculous. Could this be a sign that my camera has a bigger problem?

It seems related to shutter speed. When shooting a black image at 1/250s I get nothing. When shooting the same setup but 1s, I get a few of them. The more I increase the shutter speed, the more crazy pixels I get.

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    \$\begingroup\$ That looks normal, this is why most cameras have a "long exposure noise reduction" option which performs a dark frame subtraction to remove such hot pixels. \$\endgroup\$ Commented Jul 24, 2015 at 22:16

1 Answer 1


For exposures longer than 1 second, you can enable Long Exposure Noise Reduction (LENR). This is Canon's nomenclature for in-camera dark frame subtraction. When you take a photo the camera will expose the image normally and then use the same settings to create a dark frame with the shutter left closed. The readings for each pixel in the dark frame will be subtracted from the reading for each pixel in the first frame before sending the raw data to your memory card.

Be aware that the time required for a dark frame is the same as the time required for the initial exposure - so if you shoot a 30 second exposure you will then have to wait an additional 30 seconds before you can take another shot!

  • \$\begingroup\$ Actually I've been using this parameter without understanding exactly what it was doing to my pictures :) I guess I just witnessed a phenomenon that have been taking place in my cameras for ages... I'll live with it now I understand what it is :) Thank you for your answer. \$\endgroup\$
    – Andy M
    Commented Jul 25, 2015 at 17:29

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