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11-29-2013, 11:00 AM   #1
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Long exposure hints needed

Hi all,

I just got a shutterboss for my K-5 and plan to so some astrophotography.
When I tried a long exposure I put the camera in bulb mode.
This indicates that shake reduction is disabled.
So when I did the shot I could hear some noise inside the camera...not very loud but noticeable.

So my question is does this hurt the camera?
If I do a twenty minute exposure will this drain my battery?
I'd like to do several on a session if I can.

thanks,

Vince

11-29-2013, 11:06 AM   #2
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The SR mechanism always stays on to keep the sensor locked in place, so no, this won't damage your camera. A 20 min exposure won't kill your battery, I don't think, but I would definitely recommend bringing an extra battery to a long shoot.

Adam
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11-29-2013, 11:48 AM - 1 Like   #3
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QuoteOriginally posted by Lloyd_Christmas Quote
... If I do a twenty minute exposure will this drain my battery? ...
Why such a long exposure? If you are trying to get star trails, you can use multiple shorter exposures and stack them with free software from www.Startrails.de-Home. If you are on a tracking mount and trying to capture dim objects, see DeepSkyStacker - Free
11-29-2013, 01:00 PM   #4
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I don't think anyone does 20 min exposures for astrophotography? They might do many short ones, up to a couple minutes, but I doubt they get over 5 min for a single shot? Everything would be blurry and overexposed. I think they just take many short photos and then use software to combine them and reduce noise.

I took this photo in a city to get some stars:
http://500px.com/photo/50888178
It was under 25 seconds and that's not even the milky way, just random sky. It was almost overexposed. I think a 20 min exposure would be dangerous to the sensor (overheating) rather than the battery.

Btw, you can try the Pentax O-GPS with its astro tracer function, apparently its pretty great.

11-29-2013, 01:42 PM   #5
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Thanks for the help guys,
Sorry for the confusion, I need the long 20 minute stuff for the foreground which I will have to combine with another exposure for the stars.
11-29-2013, 02:15 PM   #6
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QuoteOriginally posted by Lloyd_Christmas Quote
Sorry for the confusion, I need the long 20 minute stuff for the foreground which I will have to combine with another exposure for the stars.
Depending on where you are and how far away the foreground is, you can sometimes get the stars and foreground in a single exposure by shining a flashlight onto the foreground. This obviously won't work if the "foreground" is a distant mountain.

20 minute exposure shouldn't damage the camera, though. The sensor may heat up a little and increase noise but there's no harm in trial-and-error to find the best combination of ISO and exposure length.
11-30-2013, 12:15 AM   #7
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If you're looking to blend a foreground image in then just set up earlier before the last ambient light fails and collect your foreground shot. Then you wait for your stars. This way you don't have that odd and unnatural looking flashlight lit foreground.
11-30-2013, 08:01 AM   #8
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QuoteOriginally posted by DeadJohn Quote
Depending on where you are and how far away the foreground is, you can sometimes get the stars and foreground in a single exposure by shining a flashlight onto the foreground. This obviously won't work if the "foreground" is a distant mountain.

20 minute exposure shouldn't damage the camera, though. The sensor may heat up a little and increase noise but there's no harm in trial-and-error to find the best combination of ISO and exposure length.
Thanks!
I must say the sensor noise is unsettling but there's nothing I saw in the manual that says you cannot do really long exposures. I'll do one at home to see what it does to the battery. I only have two battery packs.

11-30-2013, 11:47 AM   #9
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QuoteOriginally posted by Na Horuk Quote
I think a 20 min exposure would be dangerous to the sensor (overheating) rather than the battery..
OK, you have my attention on this! I will be in a cold environment as I'll be in the outdoors in California trying to photograph what's left of the comet Ison.
I think I'll consult the manual one more time about long exposures..

BTW, this is my source of how to do the combination of sky and foreground shots:

Introduction to Landscape Astrophotography


Note: the manual said there is no limit on how long the shutter can be held open but it also recommended to use the AC adapter because it drains the battery...

Last edited by Lloyd_Christmas; 11-30-2013 at 11:54 AM.
11-30-2013, 12:24 PM   #10
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Well I don't have any empirical data to back up my fear, but sensors get hot during long exposures. I think this causes hot spots and extra noise. There is also the little warning that the camera can give you when it senses temperature is too high (little thermometer icon). I've only ever seen this icon when I was using a lot of live view and taking photos on a long hike on a very hot summer day. I just connect these things and think that there might be a point where its too much. But again, I don't actually know and have heard of no such cases.
Either way I would be really interested in seeing some results from your project, it sound great
11-30-2013, 05:39 PM   #11
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A stack of shorter exposures is preferable for a variety of reasons which include:

- less shot noise per image
- ability to shoot in more light polluted skies without overexposing the sky
- less reliance on perfect tracking of mount + camera
- a large stack removes most of the noise

The K series cameras are noted for their low readout noise already which means they are very suited to astrophotography usage. Having said that a stack of shorter exposures is preferable, it should be noted that dim deep sky objects will still need a long cumulative exposure to image well. The minimum exposure benchmark used by veteran astrophotographers is 5 minutes but it is often much longer than this for distant galaxies. Chopping it up into shorter exposures just makes it easier (except for the stacking processing times!).

Too bad ISON didn't make it through perihelion intact. Any remnants will be quite dim.

Jack
11-30-2013, 06:58 PM   #12
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A little off topic, but does anyone know if the k5 series does the noise reduction post shot like my k7 does with exposures longer than 30 seconds?

I looked for info in the k5iis manual but couldn't find it.

Thanks,

Bill
11-30-2013, 10:39 PM   #13
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QuoteOriginally posted by Snydly Quote
A little off topic, but does anyone know if the k5 series does the noise reduction post shot like my k7 does with exposures longer than 30 seconds?

I looked for info in the k5iis manual but couldn't find it.

Thanks,

Bill
There's a menu setting for that. I think it's called "Slow Shutter NR".
12-01-2013, 01:22 AM   #14
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From the K-5 and on, this can be turned off by deactivating the "Slow shutter speed NR".

Jack
12-01-2013, 05:17 AM   #15
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Got it guys, thanks. Didn't put 2+2 together in my head when I set those the first time. There's a term more often used I was thinking would be in the menu's. I think it's DFS, Dark Frame Subtraction?
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