[Big G]

All,

I've got myself a B+W 10 stop filter to smooth that water and blur those clouds. Everything so far is going well, the first four photos on my Coast set on Flickr show some basic shots:

_IGP5244 on Flickr - Photo Sharing!

However, whenever I want to preview the shot, it takes a good 20 seconds before I can preview the shot after a 30 second exposure. Similarly, I can't activate the shutter again for another 20 seconds or so?

Is this a function of the K20D and I need to live with it? or is there a setting I can change? Is this a memory card function?

Thanks

[alohadave]

That's the long exposure noise reduction. You cannot turn it off on the K20D. I believe it activates on longer than 15 seconds, but your manual will tell you for sure.

[Ash]

Dark frame subtraction requires an equal amount of time that the original exposure went for to perform the noise reducing function for long exposures.

[BPT]

I have wondered why it takes an equal time to do dark frame subtraction. If the dark frame was taken immediately after the sensor should not have cooled much, and if it takes a photo of equal exposure time to do the dark frame it should actually be hotter than the sensor was in the first exposure.

I dont know if that was totally coherent.

[alohadave]

I have wondered why it takes an equal time to do dark frame subtraction. If the dark frame was taken immediately after the sensor should not have cooled much, and if it takes a photo of equal exposure time to do the dark frame it should actually be hotter than the sensor was in the first exposure.

I dont know if that was totally coherent.

It's a reasonable question, but it does the same length exposure to correct for amp noise which won't show up until the sensor has been active for a long enough time. The sensor will cools down pretty quickly if you aren't using it constantly.

The dark frame also corrects for hot pixels which show up in long exposures.

[Black Magic]

I don't have anything to add to the sensor discussion, but I must say the photos on your flickr page are excellent. Did the majority of them require longer exposure times, say longer than 30 seconds?

[kittykat46]

When Long Exposure Noise Reduction (aka DFS) first became available in Digital cameras, they were touted as a marketing point. Clean long exposures !

Before that, the manufacturers just locked away any exposure above 2 seconds, or those that did allow it had noise the size of golf-balls (exaggerating a bit).

[Big G]

I don't have anything to add to the sensor discussion, but I must say the photos on your flickr page are excellent. Did the majority of them require longer exposure times, say longer than 30 seconds?

Only the first four of the shots of my Coast photos use 30 second exposures to ice the water and blur the clouds, the others are all probably around 0.5 of a second or around 1/10 or 1/30 depending on how much light is falling on the foreground.

[WheresWaldo]

Have you tried using the multi-exposure mode to smooth the water and blur the clouds. Works without the huge filter and very slow shutter speeds. No waiting for dark frame subtraction or preview images.

Some restrictions apply, and your mileage may vary.

• Must use a tripod (but you were already doing that if your using long exposures)
• You should use a remote (wired or IR)
• You may only take a maximum of 9 frames (you can take as little as 2)

With camera on a tripod and set to take the image here is how you do it:

1. Press the Menu button
2. Navigate down to Multi-exposure
3. Navigate right to select Multi-exposure
4. Navigate right then down to the number of exposures, press OK to confirm
5. Navigate down if you want to auto-adjust EV
6. Press OK twice to exit menu
7. Press the shutter release on the remote
8. Each successive frame will be added to the next until you have taken the predetermined number of frames
9. Once complete all frames will be saved as a single image.

5 to 9 frames of the same scene with clouds or other objects moving will blur them while stationary objects will be sharply in focus. You can take a series of images at more normal shutter speeds and then combine them to simulate the use of a neutral density filter.