2

I've got a Canon 1100D camera which is maybe getting on a bit at about 12 years old, but it's performed great up to now. I took it out recently though to do some long exposure night shots, and noticed a sea of stuck pixels that seems to have appeared from nowhere. Here's a zoomed in portion of a 30 sec ISO 3200 shot I took with the lens cover on that shows the problem. This is the same all across the sensor:

Stuck pixels

Looking back at some similar dark frames I did over a year ago, there are zero stuck pixels. Since then, the camera's mostly been in storage with the battery out, save for maybe 3 or 4 daytime sessions where I didn't notice the problem.

So is there a reason why a camera might suddenly pick up a load of stuck pixels like this even when it's barely being used? And is there anything I can do about it (I've tried running the built in sensor clean a few times and it does nothing). Or maybe it's time to finally get an upgrade.

el_zilcho
  • 21
  • 1
  • Did you check that you get the same stuck pixels in different dark frames? – xenoid Sep 30 '22 at 10:46
  • @xenoid Yes, just did another shot and compared to yesterday's - exactly the same pattern. – el_zilcho Sep 30 '22 at 11:47
  • Are you saving raw files or JPEGs? How are you viewing them? Do you have Long Exposure Noise Reduction (LENR) enabled or disabled? What happens if you take a very short exposure with the lens cap on when the camera is first turned on after having been off for several hours (and cooled to ambient temperature)? – Michael C Oct 03 '22 at 16:19
  • Related: What's the best way to deal with hot/stuck pixels in long exposure night photographs? and Hot, stuck, or dead pixels. What's the difference? – Michael C Oct 03 '22 at 16:35
  • Does the time/date remain correct when you store the camera for months with the batteries removed? – Michael C Oct 03 '22 at 16:39
  • @MichaelC I've done both Raw and Jpeg - it appears the same on both formats. I've viewed them on the camera screen, and on two different laptops - all the same.

    I have LENR disabled - this would probably fix it, but I don't like the delay it causes and I prefer to do dark frame processing manually. Also I've been using this camera a lot with bulb exposures.

    For typical daytime settings (e.g. 1/100 and ISO 400) the issue doesn't appear at all. Can also confirm, looking through my recent daytime shots, no stuck pixels appear. It only seems to become prominent for longer shots at high ISO.

     – el_zilcho Oct 04 '22 at 08:27
  • @MichaelC ...and the date/time has drifted with the battery out. – el_zilcho Oct 04 '22 at 08:32
  • If they do not show up in a lens cap shot at 1/100 ISO 400, they're not stuck pixels, they're hot pixels that are affected by the heat created by the long exposures. I suspect it might be possible that your previous "clean" long exposures had LENR turned on? – Michael C Oct 04 '22 at 10:24
  • Does the time/date "drift" (off by a few seconds or one or two minutes) or "reset" (off by days/months/years)? – Michael C Oct 04 '22 at 10:25
  • @MichaelC Oh I see, good to know - I also just tested it in live view, and during movie shooting, and they don't show up at all there either. The old shots definitely didn't have LNER - they are dark frames from a session where the camera was attached to a telescope, doing 3 minute exposures on Bulb with a remote timer. I've had LNER turned off as long as I can remember.

    With the date/time, I can't remember fully but I think it did completely reset, then earlier this year I put it back to the right value, then after a few more months of storage it has drifted out by a couple of months.

     – el_zilcho Oct 04 '22 at 11:09
  • If the date completely reset, the camera's volatile memory probably also lost the most recent pixel mapping that had been stored. If the 1100D/Rebel T3 has a user replaceable backup battery, you probably should replace it. – Michael C Oct 04 '22 at 20:55
  • I find it incredible that you can take three minute exposures with any Canon camera from a decade ago and not wind up with a noticeable number of hot pixels. My 5D Mark III has quite a few that show up, even with fairly short Tv (1/60, 1/160) at ISO 3200 in dark environments where there are a lot of dark areas in the scene. With longer exposures (15-30 seconds or more) doing astro work, they're even more noticeable without LENR. – Michael C Oct 04 '22 at 20:59
  • Yes it is quite strange that I haven't had the problem until now. Maybe it's because I was doing the long shots on cold nights, often below zero. Also I've always stacked a bunch of frames with darks and bias added, so if anything was there it would have gone by the time I actually saw the result. – el_zilcho Oct 05 '22 at 08:51
  • That makes sense with the battery. On the 1100D they've placed it so that the case has to be taken apart to access it - but looking at the datasheet for the cell they use (MS614SE) apparently it's rechargeable and can do 100 deep discharge cycles. Maybe I just need to leave the main battery in for a day or so and it could be back to normal. Either way, it doesn't look like I can re-map my hot pixels using the manual clean method as they don't show up on short exposures - so probably have to rely on subtracting darks from now on. – el_zilcho Oct 05 '22 at 08:55

1 Answers1

2

I'm not aware of any common cause for stuck pixels appearing.

Many report that Canon bodies attempt to map out hot pixels during manual sensor cleaning. The method is to place the camera into manual sensor cleaning mode for ~ 10 seconds. It may help, and it may take a few attempts... there are a lot of videos/etc about it online.

The other potential fix is to record raw images; because some (most?) raw editors look for hot pixels during demosaicing the raw data and automatically map them out. Adobe Camera Raw does this (LR/PS/Bridge); but only for single stuck pixels in isolation (because pairs could be scene detail).

Steven Kersting
  • 17,087
  • 1
  • 11
  • 33
  • 1
    To remap hot pixels with the camera (Canon 1100D), the manual sensor cleaning mode must be left open for at least 30 seconds. One should also use a body cap in a dark room. If light strikes the sensor during manual cleaning mode most hot pixels will not be mapped out, because the entire sensor will have full well values. – Michael C Oct 03 '22 at 16:54
  • 2
    I've tried the manual cleaning thing many times now - all with the body cap on, sometimes for 30 seconds, sometimes for 2 minutes and longer. It makes no difference at all on my camera sadly. Yes I normally shoot in Raw, and the issue doesn't affect images with daytime settings - only long exposures. Maybe I will just have to always take a dark frame afterwards and manually subtract it. – el_zilcho Oct 04 '22 at 08:33