Hot pixels

Back in June I noticed that we had a bunch of large-aperture/high ISO exposures with a bright pink dot in the middle of the frame.  It was consistently reproducible at ISO 800 or higher at f/1.8, but there was no problem evident at lower ISO or small apertures.  A quick google search revealed that this was what's known as a "hot" pixel, and is an inevitable and common problem with digital cameras sensors.  I then did a long exposure   of the back of our lens cap (with long-exposure noise reduction turned off), and found that we had a whole bunch of bad pixels, though it was just the one magenta one that was particularly noticeable.  Once a hot pixel develops, there does not seem to be any way to fix the sensor itself.  However, sensors have millions of photosites, and so hot pixels can be individually mapped out, with the value for that pixel then interpolated from nearby photosites.

Our camera was still under warranty, so I sent it back to Nikon to have the hot pixels mapped out.  UPS Ground to the service center cost about $20, but the camera returned about 10 days later in absolutely perfect condition.  Nikon cleaned it so well that I would have sworn it was a brand new camera if it hadn't had the same serial number.  And of course, all of the bad pixels were mapped out.

Since we got the camera back, we've been taking plenty of wide-open high-ISO shots with no hot pixels to be found... until last night.  Another bright magenta pixel, right in the middle of the image!  Our camera is just out of warranty now, and I didn't want to be without it for another week-and-a-half anyway, so I searched for another solution.  I quickly stumbled across some great free software.  Pixel Fixer will automatically detect hot pixels, remember the locations of them, and then conveniently map those out of your raw files, in batches of a directory at a time, with filters for shutter speed and ISO (among other things).

See that little dot on Ashley's shoulder?  That's our new hot pixel.