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07-19-2008, 06:47 PM   #1
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Long exposure problems

I have a K100D Super.
I wanted to do a long exposure of 2-3 hours out in the bush one night but ran out of battery power after a short period of time.
With my old Pentax KM (film) I had a mechanical shutter with no problems.
Is it possible to do a 2-3 hour long exposure with a DSLR.

07-19-2008, 09:16 PM   #2
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Use an AC adapter

For an exposure that long, you'll need to use an AC adapter. The camera will keep the shutter open as long as there is juice.

Also, be aware that the NR function will need to operate at least as long as the exposure is. IE 1 hour shot will also require 1 hour for NR.
07-19-2008, 09:42 PM   #3
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Hi wombat,

I tried that a few times and got the same result each time... a perfectly white picture.
Exposures that long seem to overwhelm the sensor with noise and don't give you a decent picture.
If anyone else has gotten good results with such long exposures it'd be good to hear from you.
Otherwise, I think the only way to get things like star trails are to overlay several 30s-1min exposures upon each other.
07-20-2008, 12:03 AM   #4
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Original Poster
QuoteOriginally posted by Ash Quote
Hi wombat,

I tried that a few times and got the same result each time... a perfectly white picture.
Exposures that long seem to overwhelm the sensor with noise and don't give you a decent picture.
If anyone else has gotten good results with such long exposures it'd be good to hear from you.
Otherwise, I think the only way to get things like star trails are to overlay several 30s-1min exposures upon each other.
Sounds like technology has gone backwards when it comes to this.
30s-1m, hell I want 2-3 hours.

07-20-2008, 02:30 AM   #5
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Me too - tried some astro-photography once and gave up I have considered getting the MZ50 out to try it with actually. Some of the shots I have seen are amazing
07-20-2008, 07:53 AM   #6
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CCD and CMOS sensors are linear. Film has a non linear response curve (photons captured vs time) - this is the 'S curve'. What that translates to is this - if you want to do a 2hr or 24 hr integration of photons (the picture you're attempting) just take lots of short exposures and add them together in your favorite photo editor - CMOS and CCD have linear response curves.

Make sure that your short exposures are long enough to caputure a litlle of what you are interested in (say Orion's Nebula in the sky) and not so long as to overexpose the sky itself. Realistically this means something on the order of 20 sec to 300 sec per exposure. Much more detail than this response can go into. Astrophotography is a rather deep and addictive subject.

Last edited by JackBak; 07-20-2008 at 07:57 AM. Reason: typo
07-20-2008, 08:29 AM   #7
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I've done it twice with my K10D

First with 34 minutes exposure and it was taken in the middle of the nothing. I was with some friends on the road and we stopped in the darkest place we found...


Second time it was a small town with almost no lights, but the full moon was a little bright, anyway, 15 minutes exposure... (and polarizing filter)

All you need is a very dark night -with stars of course- The darker, the better


LINK





LINK 2

07-20-2008, 09:17 AM   #8
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Andres,

You have much darker skies available to you than most of us up here in the light polluted States. Very nice. Nice demonstration of how longer exposures can be had without blowing out the sky if you are at a dark site. By the way note that your first image's light trails are about twice as long as the second shot - corresponding to a 34 min vs 15 min exposure. Note also that your first shot caught a nebula or possibly a star cluster (smudge of light 1/3 in from the right edge of the shot).

07-20-2008, 01:14 PM   #9
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OK, now I've seen it!
(Relatively) long exposures on a K10D - and they worked!
Andres - did you need to do much to the images afterwards to remove noise?
I tried even a 30min exposure with my (then) K100D and still got a totally white result - this was trying to just shoot the dark sky (no moon) with a tree taking up a small corner of the photo.
Haven't tried it since, but will now that you've shared these results...
07-20-2008, 02:28 PM   #10
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Would an ND filter be useful to lower the light level for this type of shot?
07-20-2008, 03:35 PM   #11
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QuoteOriginally posted by JackBak Quote
Andres,

You have much darker skies available to you than most of us up here in the light polluted States. Very nice. Nice demonstration of how longer exposures can be had without blowing out the sky if you are at a dark site. By the way note that your first image's light trails are about twice as long as the second shot - corresponding to a 34 min vs 15 min exposure. Note also that your first shot caught a nebula or possibly a star cluster (smudge of light 1/3 in from the right edge of the shot).
Jack, I'm from Buenos Aires, it's the biggest city here in Argentina and the skies are quite lighted up by the city lights, For the 1st we were about 190 Kms (110-120Miles) away from Buenos Aires and for the second... I was beside the Andes mountains in a very small town.
So all you need is Love I mean... To go out a little far


QuoteOriginally posted by Ash Quote
OK, now I've seen it!
(Relatively) long exposures on a K10D - and they worked!
Andres - did you need to do much to the images afterwards to remove noise?
I tried even a 30min exposure with my (then) K100D and still got a totally white result - this was trying to just shoot the dark sky (no moon) with a tree taking up a small corner of the photo.
Haven't tried it since, but will now that you've shared these results...
ASH: the "post" time is the same that the exposure... and it is NOT nice nor funny when you wait 30 min to see the photo and it's horrible or almost empty of stars :P To avoid the "White sky"... same answer that before...

QuoteOriginally posted by Moo Quote
Would an ND filter be useful to lower the light level for this type of shot?
Moo, with the ND you'll only get less stars, For example, the 34 minutes photo was a No Moon,,, it was taken at F:3,5 and the second was at F:8 WITH a polariser because it was a Full Moon night and there was too much light... As you can see, the second has much less stars...
07-20-2008, 11:51 PM   #12
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QuoteOriginally posted by Ash Quote
Hi wombat,

I tried that a few times and got the same result each time... a perfectly white picture.
Exposures that long seem to overwhelm the sensor with noise and don't give you a decent picture.
If anyone else has gotten good results with such long exposures it'd be good to hear from you.
Otherwise, I think the only way to get things like star trails are to overlay several 30s-1min exposures upon each other.
Ash, your last comment is on the money. Art Wolfe (who does quite a bit of star trail photography) recently wrote that he knows of software which combines multiple shorter exposures for use when shooting star trails with a DSLR–but he just goes back to film for shooting really long exposures the old school way!

Last edited by christinelandon; 07-21-2008 at 12:51 AM. Reason: correction to Wolfe comment
07-21-2008, 12:32 AM   #13
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I saw a freeware once (cant remember the name, sorry) which was made specificaly for combining multiple short exposures of nightsky to get the long star trails. Results looked same as oldschool long exposures. If I only could remember...
07-21-2008, 12:38 AM   #14
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QuoteOriginally posted by Andres Quote

This would make for a fantastic wallpaper, Andrés.
07-21-2008, 03:29 AM   #15
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Try using StarMax to create composite star trail images

StarMax - Easy StarTrails Creator

If you search on ebay for "Aputure Timer Remote Cord" you'll find this:
QuoteQuote:

MORE to a shutter release cable! Gadget Infinity brings you this extraordinary Timer Remote Cord packed with functions of:
Timer – Long/Delayed shutter for up to 99 hours and 59 minutes!
Bulb mode – comes with handy lock-in switch to Hold for bulb or B-mode
Half-press AF auto focus
Shutter countdown before release/close – with beep indicator (with speaker ON/OFF)
Indicator for battery level
Backlight – Clear lit LED display control screen. Great for night wildlife or portrait shooting.

Take this exclusive Timer Remote Cord with more flexibility and control on your remote shooting trips. This cable comes with a stylish design with a comfortable hand feel holding remote.
Seems like DealExtreme has one too - $42.50
http://www.dealextreme.com/details.dx/sku.13891
QuoteQuote:

YONG NUO remote cord set to achieve the following features:
Self-timer shooting
Precise gap fixed time
Long time exposure fixed time
Remotely controls the shutter switch

Supported cameras:
TC-C1——CANON 450D/400D/350D/300D, PENTAX K20D/K200D/K10D/K100D

Last edited by freeload; 07-21-2008 at 04:06 AM.
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