I was looking through some photos taken a couple months back and noticed several small colored dots in the images taken with prolonged exposures (red, blue, etc.).
I put the lens cap on and took two exposures. The first was at 1 second @ f2.8 and there were no visible issues at 100% magnification.
The second exposure was at 25 seconds at f2.8 with the same ISO. In this image, at least 5 colored dots are shown on the image and this has been repeated with the same results.
Does anyone know what's going on here and/or have any recommendations?
I purchased the D700 about 6 months ago and would like to get this taken care of but would like to know more about it before sending it in, for example.
Any responses would be appreciated.
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#1. "RE: D700 Pixel Problem" | In response to Reply # 0TiggerGTO Nikonian since 22nd Feb 2006Thu 31-Dec-09 02:20 PM
This is exactly what long exposure noise reduction is for. During long exposures, the sensor tends to heat up which can cause pixels to be stuck on. If you turn on long exposure noise reduction in the shooting menu, this will cause this process to occur for exposures greater than 1 second. When this happens the camera is not usable for the amount of time that the exposure it just took was. So for a 25 second exposure, the NR processing takes 25 seconds.
I don't remember what the threshold is for normal vs problematic sensors, but having some stuck pixels after a 25 second exposure without using long exposure noise reduction does not surprise me. Hopefully there are others that will post with more definitive information than I can provide.
A Nikonian in North Carolina
#2. "RE: D700 Pixel Problem" | In response to Reply # 0FThompson Registered since 29th Apr 2008Thu 31-Dec-09 02:35 PM
Second what Danny said.
The camera uses the second exposure to identify "noisy pixels" which the camera uses to subtract those from your original shot.
An alternative when shooting long exposures (mins, hrs) is to turn the long exposure NR in camera off and just do one "noise" capture at the end. This can be done with the lense cap on so only noise is recorded. The noise capture is then fed to the software package to let the software eliminate the noise. This mimimizes the non-productive time when shooting.
shoot an hour exposure, wait an hour for NR,.....
shoot an hour, shoot another hour,......,shoot an hour with the lense cap on.