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After half a year of use of the camera I found my first hot pixels. It was always present but in normal photos you probably wouldn’t see it out of 5 million pixels. It was a cluster of always-green pixels. The image is taken at 1/30 second, with the lens cap on.

Last month I’ve been reading about programs who could read the pixels and about a program remapping the dead pixels. And after a successful firmware upgrade, I decided to give it a try.

The first utility is the DeadPixelTest program. This program can find do two things:

1. Hot pixels. Hot pixels are pixels that become bright on your photo. On my tests these are visible as green, blue, magenta and red/yellow blobs that fade away. This is a bit depending on the CCD type. The issue is that with longer exposures the individual red/blue/magenta photo sites, they cannot keep the charge and leak this. On professional cameras like the Nikon D1h/D1x the sites are much larger, can contain more charge and result in less noise and hot pixels. Because of the fact that the green sites are double of the other, the possibility of a green hot pixel is much higher then any of the other color combinations. So hot pixels are caused by long exposures but note that they also appear much faster under warmer conditions.
2. Dead pixels. This is a non functional picture and turns up white even if there is no light on the CCD.

The utility requires a photo with the lens cap on. With an excellent CCD, it would turn out completely black. Hot pixels will turn up with a certain color. Depending the length of the exposure, the more pixels will probably turn up as the photo site cannot contain the amount of charge. The photo should be stored as tiff as a jpeg can contain additional artifacts and it may look much worse. I took a number of exposures, starting with 1/30, 1, 4, 8 and 30 seconds. Do this using shutter priority mode (S). The 1/30 calculated 4 hot pixels, 1-second exposure resulted in 12 hot pixels and the 30-second expose gave me 96 pixels. I set the max resolution to cover the complete CCD, sharpening of, ISO 100. Note that under long exposure there will always be hotter pixels and the same is true for high ISO values. So you need to decide for yourselvs when you think a pixel is really hot. ALso if it snot visible on you photos, you should probably not bother.

But how to get rid of these pixels!? Should I replace my ccd? Fortunately not, there are at least two options to fix this issue. One is to send your camera to nikon repair. The other options is this little neat program, cpix map v0.12, from this Russian guy. It uses the algorithms in the Coolpix 5700 to check and remap the hot pixels. It takes between 5 and 15 minutes to read the pixels (625 seconds on mine) and around 20 seconds to program the map that maps out hot pixels. This map is used so the software eliminates the hot photo sites and the resulting pixel is replaced by the average of the surrounding photo sites.

I took a 4-second picture after the remapping and run it through the DeadPixelTester and got zero, zip, non hot pixles out of the camera. So, quite successful operation!

After the hot pixels are remappend, you can sometimes still see them in the viewfinder. This is because the re-mapping algorithm is applied after the shot. So in the evf you see that actual ccd image. After the shot the sharpening, contrast etc are applied and is taken care map out the hot pixels and use the average of adjacent ones.

This is a log of the program when reading the ‘defective’ pixels:

NIKON   NIKON DSC E5700 1.00
FIRMWARE: v583-80
S/N: 000004024402
Reading the defect pixels.
Elapsed time:   627 sec (100%).
Read  512 defect pixels.
1	350	865
2	560	424
3	2492	1484
4	2334	1158
5	747	529
 :
511	1163	1158
512	679	1885

The program stops as soon as 512 entries are found as that is the limit of the pixel map in the camera. When remapping the pixels, the utility shows this:

NIKON   NIKON DSC E5700 1.00
FIRMWARE: v583-80
S/N: 000004024402
Remapping the defect pixels.
Remap complete. (18 sec)
It's been found 512 defect pixels.

Its been doen is just over 20 seconds, you also hear the shutter so I think what actually happens is that the software starts the Coolpixes internal hotpixel detection algorithm by taking a shot with the shutter closed! Very clever!