[Ed Hurst]

Hello all,

So many of you are probably aware of the frustrating behaviour of the 645D re. long exposure noise reduction (the function where the camera takes a dark frame immediately after the exposure so it can do dark frame subtraction of noise) - the frustration is that the menu offers the option to turn this behaviour off (which is very useful when taking a sequence of shots for star trails), but turning it off doesn't stop the function from activating. It just does it anyway.

That much is well documented.

The limit seems to be 30seconds. If you expose 30seconds or quicker, no problem. Anything above that, and the compulsory dark frame is taken regardless of whether you have that function turned off. Annoying though that is, it is well known.

Now I had something even more irritating happen - compulsory dark frames with exposures of 30 seconds! That never used to happen. I recently took long sequence of 30 second exposures, and the camera started taking the dark frames - not with every frame, but with some of them. Since I was shooting for star trails, very irritating. Anyone know why this happened and how to stop it?

FYI - I have all in camera noise reduction set to off - that for long exposures and that for high ISO.

FYI - I updated my firmware to the latest version just before this happened - coincidence? Not sure...

All help gratefully received!

Ed