Long Exposure Noise

[deaner66]

<p>I've had a K10D for nearly two years now. Brilliant camera.</p>

<p>Lately, whenever I take night shots, longer exposures, my shots are filled with noise.</p>

<p>I admit up front, I don't use the NR feature because of the inconvenience of waiting for the "phantom" shot to mix with my shot. That said, the noise I now see, seems worse than ever before. And I have taken a lot of night shots with no complaints.</p>

<p>Has anyone else with a K10D had this problem? Also, I have to say, everything else about the noisy shots is crystal clear.</p>

<p>I'm kind of losing faith in my little buddy, here.</p>

[pbarnes]

<p>Steve, I took my first long night exposure with my K10D just the other night, with only a full moon for light. I did have the NR on, so when the 6 minute exposure was finished, I put the camera in the bag, still switched on, and went home. Voila! One absolutely noise free image. This is a camera that has done a fair bit of work. </p>

<p>I did see on another photo.net forum recently a suggestion that if you were doing a number of the same exposures you could do one with the lens cap on at the beginning, then the others normally without NR, and then eliminating the noise by combining them with the 'phantom' shot in your processing software. Does anyone know how this might be done in Photoshop or Elements?</p>

 

[c_wyatt]

<p>Might be terribly obvious, but I assume you're shooting at a low ISO? Are you using the viewfinder cap?</p>

<p>Peter, what's this about shooting with the lens cap on??</p>

[hagar]

<p>Steve, the only thing I have come across is that whenever I have done any kind of long exposures with a less than fresh and fully charged battery, I have seen more noise. Are your batteries new? If they are on their last legs, they may not be giving out as much juice.<br>

Another factor with long exposures is temperature.. if it's hot outside, the sensor is going to be hotter to start with.<br>

Hope this helps..</p>

[pbarnes]

<p>Camus, as I understand it, noise reduction for long exposures on digital cameras works by using a second, no light 'exposure' to replicate the noise that the sensor would have produced on the original image. So the second 'exposure' is for the same time, (and so at roughly the same temperatures), as the first, but with no light (shutter closed). In theory the second image contains only noise, and it is the same noise as in the first exposed image, so the camera can use the second image to subtract the noise in the first image.</p>

<p>The problem with this approach, and the reason Steve does not use it, is that the second long exposure must be as long as the first to accurately replicate the noise. During that time the camera cannot be used.</p>

<p>The suggestion I referred to (I wish I could find it, but no..) was to get around having to wait for the second long exposure after each shot - turn NR off, take one shot with the lens cap on for same time as your other shots, and instead of the camera using one dark image for each shot, use this one dark image for all the shots you take at that time, assuming they are all similar length exposures. The original poster suggested that this could be done in image processing software, but gave no specifics.</p>

[c_wyatt]

<p>Interesting, be good to know how to do it if anyone has the details</p>