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12-13-2013, 06:57 AM   #1
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Interval shooting with K-30 question

I am taking pix of the meteor showers and having a problem with the Interval shooting mode.
I am doing 15 sec. shots with an 18-135wr, iso400, f4.

I have the interval set at 10sec, set for 50 images.
When I start the shots, it only takes 10 pix and then says its done. When I switch to my 50mm 1.4 , lower the iso and use F2, I get about 20 shots and it says it's done.

There is plenty of battery and room on the memory card. Is it because I'm using a long exp. or ?

12-13-2013, 07:06 AM   #2
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Could it possibly be related to the Long Exposure Noise Reduction filling up the buffer?
12-13-2013, 07:32 AM   #3
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QuoteOriginally posted by tomwil Quote
Could it possibly be related to the Long Exposure Noise Reduction filling up the buffer?
I'm starting to think that's the reason. After searching some more threads it looks as if I need to set the interval time between shots at least as long as the exp. time or the buffer will get full and end the interval session.
12-13-2013, 10:42 AM   #4
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The interval time is the time from the start of image N to the start of image N+1, NOT the time from the end of image N to the start of image N+1. The actual selected shutter-open time (eg 10 seconds) + any other processing time (NR and/or lens correction that occurs) must be included in the interval time. This could easily be double your selected shutter-open time. Add a few seconds to allow for variations in the "other processing time".

This just the way Pentax does it.

12-13-2013, 11:08 AM   #5
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QuoteOriginally posted by TedH42 Quote
The interval time is the time from the start of image N to the start of image N+1, NOT the time from the end of image N to the start of image N+1. The actual selected shutter-open time (eg 10 seconds) + any other processing time (NR and/or lens correction that occurs) must be included in the interval time. This could easily be double your selected shutter-open time. Add a few seconds to allow for variations in the "other processing time".

This just the way Pentax does it.
So if I want to take a 15 sec. exp every 10 seconds I would need the interval to be set at 40 seconds give or take a few?
12-13-2013, 11:55 AM   #6
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Sounds like it. But it will not be a photo every 10 seconds but a photo every 40 seconds in that case
12-13-2013, 12:18 PM   #7
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QuoteOriginally posted by Kendigitize Quote
So if I want to take a 15 sec. exp every 10 seconds I would need the interval to be set at 40 seconds give or take a few?
The real killer for long exposures is the "Slow Shutter Speed NR", which is actually a second exposure, of the same time as your original exposure, with the shutter closed (total exposure time now is 15 + 15 = 30). This sensor noise image is then subtracted (negating sensor noise) from the original exposure. Your camera cannot take the next regular exposure until this is accomplished, as there can be no overlap of these exposure operations. Note that you should be able to turn "Slow Shutter Speed NR" OFF, but I'm not sure for the K-30 (I use K-5, where it's a Record Mode setting). Then there would be no 2nd exposure time required.

Filling the buffer is not the problem. It's having the total exposure (some hidden for NR) time being greater than the interval time, and the "Slow Shutter Speed NR" has a default of AUTO, with exposures of 1 second (K-5) adding on the 2nd sensor noise exposure.

Take 1 image at your desired exposure time, without using the interval record mode setting, and look at how long it actually takes before the camera is fully ready for another. Enabling Instant Review will show you that time, when the image pops up on the LCD. Set the interval to be a bit greater than this. Try a couple of interval exposures to ensure that there is no overlap. Then take your interval images. That's what I do for my star shots, where a minimum interval time is not required.

Other processing time (lens correction, SD card write time) can add to the problem, if the camera cannot perform these operations in parallel with the next exposures. That's why tests may be needed to ensure that the intervals don't end up overlapping. Overlap will reduce the number of shots from the expected (shots are skipped), and the actual images will not be uniformly time-spaced. Pentax doesn't give you much automatic help in avoiding this overlap. If your camera can overlap these processing operations with the next exposure times, you can reduce the interval time, but getting to a minimum interval time will require the testing.

And try explicitly turning off "Slow Shutter Speed NR" to see if your images even need it or not. That would enable you to speed up your interval, but may increase the noisiness of your images. Your choice. Star shots may need it. Long exposures to get silky ocean waves during a sunset probably don't.
12-13-2013, 12:55 PM   #8
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" Note that you should be able to turn "Slow Shutter Speed NR" OFF, but I'm not sure for the K-30 (I use K-5, where it's a Record Mode setting)."

The Slow Shutter Speed NR is is Rec Mode 3. There are 3 options: Auto, On, Off.

Regards

12-13-2013, 02:08 PM   #9
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Thanks for the help. I think I get it now. Here's a sample of what I came out with and you can see the gaps where I was tring to figure out the settings. Tonight I hope to catch some meteors from the Geminids. I saw plenty that streaked into my shots, but they were barley visible in the photos.

Last edited by Kendigitize; 02-15-2014 at 09:42 AM.
12-13-2013, 02:18 PM   #10
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QuoteOriginally posted by bluenose Quote
" Note that you should be able to turn "Slow Shutter Speed NR" OFF, but I'm not sure for the K-30 (I use K-5, where it's a Record Mode setting)."

The Slow Shutter Speed NR is is Rec Mode 3. There are 3 options: Auto, On, Off.

Regards
Yes, you can turn it off on the K-30 too.
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