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11-04-2010, 10:52 PM   #1
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Interval shooting on the k-7

Hi all,

I set up my camera tonight in an early experiment to try making a star trail image. I used the onboard interval shooting function to tell the camera to take 98 successive exposures at 25" each pointed at the sky from my backyard, and walked away for 40 mins for it to do its thing. It seems it only took 51 of them though. For clarification, the camera battery did not run out of juice; the interval shooting apparently just aborted halfway through.

Does anyone have any experience with this or understand what's going on?

Thanks!

btw:



11-04-2010, 11:04 PM   #2
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If AF is turned on it tries to autofocus for each picture. If it fails because there is little to focus on it can also drop that picture. If you haven't done so, try with camera set on manual focusing.
11-05-2010, 12:30 AM   #3
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run out of memory?
11-05-2010, 02:24 AM   #4
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I gather you set the shooting interval at 25 sec.
What was your exposure time setting, and what was your Long Exposure Noise Reduction setting ?

If it was On, and your exposure time was set at, more than 13 seconds (more than 1/2 of 25 secs) at some point DFS NR could have kicked in and locked your camera for more than 25 secs. When camera tries to take the Interval shot at the 25th second, it will fail...and Interval shooting stops there.

Just sharing a previous experience. The solution I found was to make sure Long Exposure NR is Off, with a bit more work needed on Noise Reduction in PP.

11-05-2010, 07:43 AM   #5
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QuoteOriginally posted by kittykat46 Quote
I gather you set the shooting interval at 25 sec.
What was your exposure time setting, and what was your Long Exposure Noise Reduction setting ?
No, my interval shooting was set to 2 seconds. Okay maybe this is the problem; can someone help clarify? Does the interval you set represent the space of time between the beginning of exposures or is it the amount of time the camera waits after finishing one exposures before beginning the next?
11-05-2010, 09:10 AM   #6
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Hello,

To understand what's going on, I'd suggest playing around with various configurations 1) expT > I, 2) expT = I and 3) expT < I where expT is exposure time and I is interval. I think you'll find that this is at the root of your issue. Basically the intervalometer is independent of your exposure time, they run in parallel. So if your exposure time (or exposure time + NR if you have it on) exceeds your interval, your cam gets upset and misses some out because 'hey I'm already busy'.

Sorry I'm at work so don't have my notes with me but I think offhand the # of images recorded if expT > I is (n/2) +1 where n was the # you set. Or maybe it's (n/2)-1, I just can't remember. But what's going through the cam's head is something like this:

1) start intervalometer
2) wait I
3) do expT
(4) (if next I encountered during expT then miss out on that exposure and I {ie #2 in that I series), wait till expT done, the go on to the next I{ie #3 in that I series})
5) resume I
6) do expT
(7) (if next I encountered during expT then miss out on that exposure and I {ie #4 in that I series), wait till expT done, the go on to the next I{ie #5 in that I series})
etc

FWIW, for startrails I personally use 'continuous' shooting mode (30s shots continuously pumped out one after the other), forget the intervalometer.

Last edited by Nass; 11-05-2010 at 11:35 AM.
11-05-2010, 02:15 PM   #7
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When does the dark-frame noise reduction kick in again? At 30s exposure and above, right?
11-06-2010, 12:38 AM   #8
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QuoteOriginally posted by fewayne Quote
When does the dark-frame noise reduction kick in again? At 30s exposure and above, right?
Depends on the Slow-Shutter NR setting.
If its Off, on the K-7 it will be forced above 30 seconds.
If its On, it is unpredictable - it will kick in when the software logic considers the noise to be above a certain threshold - the K-7 manual mentions factors such as shutter exposure time, sensor temperature, ISO setting...

11-06-2010, 04:25 AM   #9
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QuoteOriginally posted by v5planet Quote

... for 98 successive exposures at 25" each pointed at the sky from my backyard, and walked away for 40 mins for it to do its thing. It seems it only took 51 of them though.

... the interval shooting apparently just aborted halfway through.
1. Presumably you mean 25 seconds duration each exposure?

2. And what delay interval between? (sufficient for DFS to do its antics, if it deemed reqd? Surely the sensor would cook on that heavy job, or would it?)

3. Aborted "halfway through"? By that do you mean after 51 * (25 + interval) in succession, then it went to sleep, or ... ?

4. Have you plotted the Exif timestamps of each of the 51 over the possible 40 minutes unattended duration automated cycle to get indication of dropoff frequencies, or absolute dropout time, etc?

.R.

Last edited by Hypocorism; 11-06-2010 at 04:35 AM.
11-06-2010, 01:24 PM   #10
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On the K7 the DFS can not be disabled, and it should start at around 10 seconds of exposure. So if your exposure time is 25 seconds, you will have the main exposure and the DFS exposure (50 seconds total), which after 40 minutes would be around 50+ frames.

I do not see any gaps in the star trails in the image so, I get the feeling that this was a stacked set of somewhat near continuous frames.

You can also use and external shutter release systems such as this. You can set the number of images, interval time, etc.

Pentax uses the same connector as Canon. Also, even if the camera turns it self off between images, the camera will turn itself on and take the next image when initiated by this unit (or any external shutter release).

11-06-2010, 02:19 PM   #11
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Hello,

In fact on the K-7 DFS can be switched off at <30 seconds. So it's perfectly possible to machine gun 30s exposures one after the other continuously with no DFS gap in between. The only gap is the shutter going up and down. In B above 30s DFS can't be switched off though.
11-06-2010, 02:56 PM   #12
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I went out again last night, and I think the problem is the cache overflowing... my interval between shots is apparently short enough that after several tens of photos, the K-7 can no longer finish processing the last image before the next exposure is initiated, which cancels the remaining interval shots. I troubleshot the other potential issues -- autofocus is off, dark frame subtraction is off -- and it seems it just takes a continuous series of exposures until it hits that wall and then stops. This is a bit of a bummer, because even with my widest lens, there are noticeable gaps in the star trails when there is as little as a 2 second interval between exposures.

Maybe it's time to invest in a remote and shoot in continuous mode so it takes a break to catch up processing without giving up altogether.

Thanks all for your help!
01-16-2011, 10:58 AM   #13
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I'm in a similar situation, shooting at 25" but with a 1 sec interval between shots. Averaging 36-40 shots before the camera says that interval shooting is complete. From my understanding of Nass' post, should my interval be 26"? I am not having a problem w/ buffer speed (camera can shoot while buffering or why would burst mode work, right?)

Never realized that locking down the remote in burst mode would do the same job. Thanks. I could just go that route.

Last edited by John Araki; 01-16-2011 at 11:09 AM.
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