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Elan II wrote:
You actually raise two different issues here.
To check for dead pixels, take a shot with the lens cap on at ISO 200 and very high shutter speed, so light leaks won't have an effect. Resulting 'hot' pixels are dead.
To check how clean the sensor is, shoot the blue sky at f/22. If you don't want to wait until tomorrow, shoot a light gray surface with flash and overexpose a little, again at f/22.
The pic you posted here is not showing dead pixels.
I prefer long shutter speeds for checking sensor cleanliness. Set the camera to lowest ISO and using a wide(ish) lens at small aperture, make the exposure long enough (~1 sec.) so that the camera can be rotated maybe half of a turn during exposure. That will blur the background to prevent confounding dirt/dust with any spots on the wall, ceiling, etc. Of course outdoors with a uniform bright sky works if you have it, but I'm often checking for dirt late in the day or early in the morning in a hotel room for example.
Edited on Nov 28, 2011 at 04:28 AM · View previous versions