No, not a new place to fuel your addiction for nude pictures, we are talking sensors here! D’Arcy Norman just bought a brand new Canon 350D and was shocked to see some strange lights appear in his night time scene. Unfortunately they were not a signal from extra-terrestrials. See the thread at Flickr
I just did a test 30 second exposure with the lense cap on, taking a few shots to see if it’s a pixel thing or an internal light leak or something. Each one has the exact same 10 spots – some blue, some red, some grey. This will make night photography (esp. stars) basically useless…
These hot pixels are unfortunately a common problem and well worth checking your camera for. They appear as bright pixels in an otherwise dark scene. While not normally a problem in normally lit photographs, long exposure photographs can be spoiled by these errant dots. Hot pixels are caused by “charge leakage”.
So D’Arcy had a faulty camera? Yes and no. Hot pixels are normal and very common, but the Canon 350D in the way D’Arcy was using his camera should not have exhibited this problem to this degree. To know if it is normal or not you have to compare against another identical camera, I know my 350D camera does not do this so D’Arcy was right to return his for an exchange. Some people say ambient temperature can have an effect too.
How to check your sensor for hot pixels
To check for hot pixels, or should I say excessive hot pixels, you need to take a long exposure of a dark scene. In the thread “Rockies” recommends you take a long exposure photograph with your lens cap on. For best results you should also bump up the ISO, doing this increases the sensitivity so the signal is amplified. Do not mistake “noise” for a hot pixel though! Also if your errant pixel appears white or black in daylight shots that is not a hot pixel but a defective pixel.
Hopefully if your camera has this problem the pixels will make themselves known, if you can’t force them with this test a normal shot should look ok. If you get lots of green, blue or red spots, better get your camera checked now especially if it is still in warranty.
Fixing hot pixel affects in Photoshop
In the Flickr thread a user recommends an article that explains how to remove hot pixels from your photograph with photoshop. Personally this approach seems long-winded, I would rather paint the pixels out or get the camera repaired. There are also products that do this job for you.
Should you worry?
If you just or recently bought your camera then you should be happy with your purchase and swapping it for a less prone model is probably the right thing. If you have had your camera a while consider
- How extreme the problem is
- How often does it occur
- How expensive to fix it will be
In many cases one or two pixels will not be worth fixing and would probably not be worth bothering the repair centre for unless you routinely take night time/astronomy photographs. For most of us a couple of clicks of the brush in photoshop will more than suffice.
Technorati Tags: photography, hot, pixels, camera, problems, tips
