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06-28-2011, 09:39 PM   #1
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Bulb Mode Problem on K-x

I have a problem with bulb mode on my K-x. This has happened twice. I just took a 10 minute picture of the stars. I waited 30 minutes after that for DFS and nothing happened. The camera apparently froze and I lost the picture. I had to take the batteries out to get my K-x to work again. This is frustrating because I think it would have been a good picture, but I'll never know. Should I contact Pentax? I really don't want to be without my K-x if I have to send it in under warranty. I wish I could just turn off DFS, then I wouldn't have this problem.

06-28-2011, 11:44 PM   #2
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Same thing happened to me on bulb mode, tried to play in the night moon eclipse was (not on the moon). I thought batteries were depleted, changed them but after i got the same freeze. I did not waited though more than 2 minutes, is there a very long waiting time involved after bulb shoot?
06-29-2011, 01:18 AM   #3
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Had that problem too - exact same symptoms...

Turns out the batteries were not quite up to it. I purchased some new Eneloops and it much improved the issue but still not bulletproof for very long exposures.

However I have excellent results using Lithium batteries (like those supplied with the camera). I now keep a set spare ready specifically for very long exposures.

No problems with this since - even hour long!
06-29-2011, 02:08 AM   #4
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QuoteOriginally posted by krp Quote
I have a problem with bulb mode on my K-x. ...... The camera apparently froze and I lost the picture. ......... I wish I could just turn off DFS, then I wouldn't have this problem.
Forced dark frame subtraction seems to be more or less mandatory with modern CMOS sensors. Nikon cameras have always employed DFS and have for the same reason been considered less attractive for atstrophotography.

However, there is a rather brute way of avoiding DFS called "Nikon Mode 3":

Nikon vs Canon DSLR Cameras for Astrophotography

You simply turn the power off while the dark frame is being generated! I tried that on my K200D whith DFS activated and it actually works on my camera too.

That said, quite a lot of power is spent to keep the shutter open for 10 minutes. Thus, for shorter astrophoto sessions I use Energizer lithiums (which are also the best for low temperatures) but for long sessions I would not rely on anything else than an external power supply, (battery pack or DC power supply as circumstances permit).

06-29-2011, 02:48 AM   #5
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This DFS thing is interesting. According to tests I have seen with it turned off (versus on) with K-R and K-5, it makes very little difference.
So little as to wonder why lumber the photographer with the huge delay (could always do a DFS with software later).
06-29-2011, 03:05 AM   #6
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QuoteOriginally posted by kiwi_jono Quote
This DFS thing is interesting. According to tests I have seen with it turned off (versus on) with K-R and K-5, it makes very little difference.
So little as to wonder why lumber the photographer with the huge delay (could always do a DFS with software later).
I'm afraid that we have fallen hostages to a general public demand(?) for no-noise-whatsoever. There are indeed many pixel-peepers out there that are just searching for a bit of hot pixels and luminance noise rather than looking at the pictures as a whole.......
06-29-2011, 04:34 AM   #7
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So the wrap-up seems to be: use batteries like new Energizer Lithiums, or the AC power adapter, when doing important long exposures in Bulb mode.
07-02-2011, 10:35 PM   #8
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I hadn't thought of the battery as the problem. I was using some year old eneloops that were almost fully charged. The first time this happened, I lost a 10 minute exposure, but the 20 minute exposure after that worked.

07-07-2011, 04:13 PM   #9
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i've got the same problem and I am only letting the shutter open for 45 seconds
07-14-2011, 06:55 PM   #10
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Any chance the problem has to do with card write speed?
07-14-2011, 10:22 PM   #11
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actually, i already found the solution to the problem. In fact, there is no problem at all--when the Slow Shutter NR is on, the time it takes for the camera to process the image is the same time that I allow the shutter to be open.

So if I let the shutter open for one minute, the camera needs another minute to process the image.
07-14-2011, 11:56 PM   #12
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Interesting that the nr takes that long to process... doesn't really make any sense to be honest.
07-15-2011, 12:41 AM   #13
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QuoteOriginally posted by HalfDeadTree Quote
Interesting that the nr takes that long to process... doesn't really make any sense to be honest.
Well it does make sense - as long as you are allowed to turn it off:

It is not noise reduction in software but a "physical" noise reduction where you subtract a dark frame of equal exposure time. That way, you subtract hot pixels which would otherwise show up as "stars" in night photography.

In astrophotography and other very low light photography applications with very long exposure times of up to several minutes you would normally much prefer to take just one (or a few) dark frame(s) yourself and make that subtraction afterwards, but manufacturerers usually don't have this kind of users in mind when they design their cameras.
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