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05-29-2014, 07:48 PM   #1
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K3 , Bulb setting, and file transfer to SD

I have a K20D, have owned several film bodies (PZ-1 being the latest).

I've done, and continue to do, a lot of time lapse night-time shots. Star Trails, special effects, etc.

The K20D had this annoying 'feature' of taking 1:1 time to transfer the image to the SD card as the shot took. Ex. A 30 minute time lapse on B takes another ~30 minutes to transfer to the SD card = 1 hour per such shot. And yes, I use the fastest supported SD card that the K20D can handle.

Q. Does the K-3 have this same issue?

05-29-2014, 07:52 PM   #2
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This isn't an issue, it's a feature called slow shutter speed noise reduction aka dark frame subtraction. It can be disabled via the menu.

I recommend keeping it on for any exposures longer than 30 seconds. It works by taking a photo with the shutter closed for the duration of the original exposure, thus revealing noise caused by heat. The noisy pixels are then subtracted or removed from the original image. Hence the wait
05-29-2014, 09:54 PM - 1 Like   #3
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WestCoastGuy, consider the shooting of fireworks with a 30s shutter speed. DFS-in-camera greatly extends the time waiting between shots. The way to reduce this delay is to turn DFS off in camera, take just 1 shot with the lens cap on for 30s for a 30sec-dark-reference-frame and then subtract this in PP. The dark frame should be taken in the same session so the ambient temperature is the same. Since some sensor self-heating will occur, particularly in Sony Exmor sensors used in the K-3 & K-5, where thousands of ADCs are included around the edges of the sensor, I'd take the dark frame at the end of the session rather that at the very beginning.

https://en.wikipedia.org/wiki/Dark-frame_subtraction


The freeware raw converter, RawTherapee, has such an option:

http://50.87.144.65/~rt/w/index.php?title=Dark_Frame


If in a session you were taking both 15min & 30min exposures, then you would need to record two different dark frames.

Dan.

Last edited by dosdan; 05-29-2014 at 10:13 PM.
06-07-2014, 10:05 AM   #4
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QuoteOriginally posted by dosdan Quote
WestCoastGuy, consider the shooting of fireworks with a 30s shutter speed. DFS-in-camera greatly extends the time waiting between shots. The way to reduce this delay is to turn DFS off in camera, take just 1 shot with the lens cap on for 30s for a 30sec-dark-reference-frame and then subtract this in PP. The dark frame should be taken in the same session so the ambient temperature is the same. Since some sensor self-heating will occur, particularly in Sony Exmor sensors used in the K-3 & K-5, where thousands of ADCs are included around the edges of the sensor, I'd take the dark frame at the end of the session rather that at the very beginning.

https://en.wikipedia.org/wiki/Dark-frame_subtraction


The freeware raw converter, RawTherapee, has such an option:

http://50.87.144.65/~rt/w/index.php?title=Dark_Frame


If in a session you were taking both 15min & 30min exposures, then you would need to record two different dark frames.

Dan.
Dan / Adam,

Thank you for the comments. I had called Pentax Canada back in 2008/9 about this & was told word to the effect of "Yes, that is how it works. There is nothing you can do to change the 1:1 operation."

So, many thanks on a new technique!

I'll be trying this tonight...

06-07-2014, 02:06 PM   #5
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WestCoastGuy, good luck with your long-duration night shooting.

In the K20D, DFS was non-defeatable. In later cameras you can switch it off. In the K-3, the DFS control is under Camera menu icon, 2nd screen, Slow Shutter Speed Noise Reduction.

Dan.

Last edited by dosdan; 06-07-2014 at 02:17 PM.
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