Hot spots

[Fangman]

Just looking at some images from today having a dark background with the 40D and noticed some white pin-prick looking spots. I presume these are hot pixels. How common is this and what test do I do on my replacement camera when I get it?

 

[Janice]

There is a test here Phil

http://www.photo-freeware.net/deadpixeltest.php

 

[Steep]

How long were the exposures?

 

[RobertP]

Don't know if the 40D is the same but on my camera the noise reduction kicks in for exposures longer than 1 second - if noise reduction is enabled in the custom functions.

If I take a 10 second exposure the camera pauses afterwards to take another 10 second shot with the shutter closed....then subtracts the noise.

Simple answer is hot pixel noise is only a problem if you can see it in normal shots not special test shots with noise reduction off.