Hello all,
I went out shooting with my mother last night (me on a 7D, her on my older XSi), we were shooting long exposers if this makes a difference. When we uploaded the photos I found about a dozen pixels that we stuck on in every shot taken on the XSi. A couple red and a couple blue. I looked at some of my mother's older shots (normal exposure times) and found the same problems. Any idea what may be causing this? Perhaps any ideas of what I can do to fix it?
Thanks.
Sometime this works and sometimes it does, but give this a try:
Turn the ISO as high as it goes and take a 30 second exposure. And then with the lens cap on turn on manual sensor cleaning for the same length of time.
You can also try taking a long exposure (3 to 5 seconds) of a wall or something unevenly illuminated while moving the camera around during the exposure.
Sometimes they work, sometimes they don't
I have the same thing with my Rebel T1i - at long exposures (> 1 sec) there can be a few red & green annoying dots. I detected this when my camera was still under warranty but didn
Whether you know it or not, hot cold stuck or even dead pixels are quite common with CCD and CMOS Sensors. However, most people don't even notice it until they take a long exposure low light image where they will stick out like a soar thumb on a dark background. This is common in astrophotography and is just one reason for stacking multiple shots as well as shooting and extracting dark frames in the image stacking process.
Some raw converters include a feature to fix these hot/dead pixels. Adobe does it automatically, for example (except when using sRAW), Bibble allows you to customize the parameters. It
my 5D2 has like 6 dead or red hot pixels. I just learned to deal with it and quickly clone them out if they are really visible.
<div>Originally Posted by cls
The mentioned method is far from hokus pokus. Soon after getting my 5DII and 7D, a few hot pixels showed up. By putting on a lens cap and covering the eye piece and switching on manual cleaning for 30 seconds to a minute, the hot pixels went away. I only had to do this once on my 5DII and twice on the 7D, and at the moment I have no hot pixels. I'm sure if another comes up, this method will clear it.
Apparently the camera looks for hot pixels and turns them off, filling in their value with the average of those around it. Doing this makes a lot of sense. I'm sure it's very difficult to manufacture a sensor with 18 or 21 million pixels and have every one be perfect. Using the values of others around a hot or dead pixel is certainly reasonable.
As Daniel mentioned, some RAW converters such as Lightroom and Aperture automatically fix hot pixels, so you might not even notice. I didn't notice one hot pixel for a long time until I randomly noticed it just before Lightroom fixed it (there is a brief moment the first time looking at an image in Lightroom that you can notice hot pixels, but you better be looking in the right spot). Then when taking an all black exposure on the camera I could see it when reviewing the image on the camera. A quick round of manual cleaning with the lens cap on took care of it. Honestly it hardly matters, since my results are the same - now the camera just fills in a value for that pixel instead of Lightroom.
If the aforementioned method doesn't work for you, perhaps there's something more complicated going on or maybe your particular camera doesn't support it. I'm not sure when Canon implemented the ability for the user to map hot/dead pixels. I know it's annoying to think your image isn't perfect (I can be a little OCD at times, so believe me, I know...) but since software like Lightroom and Aperture take care of them so easily, don't sweat a few hot/dead pixels.
</div>
- Trowski
tkerr, thank a bunch. It worked like a charm.
I had the same problem on my 7D, easily noticeable on ISO800, 10-20 seconds (which is easily doable for some high-f macro shots and pinhole).
Tried the
An awful lot of electrons were terribly inconvenienced in the making of this post.
Gear Photos
Posting Permissions
Reply With Quote