Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-07-2008, 08:20 PM   #1
Senior Member
joefru's Avatar

Join Date: Mar 2008
Location: South Louisiana
Photos: Gallery
Posts: 210
Star trails and ultra-long exposures

What's the longest bulb exposure anyone here's done? My last camera completely maxed out at 60s, and I want to do some star trails. I'm guessing that a single, ultra-long exposure (30 minutes or an hour) will harm the sensor. What's the longest that's safe? I've seen some good shots that were stacked 8-min exposures, but is the K10D different at all?

Thanks.

05-07-2008, 10:28 PM   #2
Veteran Member
alohadave's Avatar

Join Date: Jan 2008
Location: Quincy, MA
Photos: Gallery | Albums
Posts: 2,024
It's not likely to harm the sensor, but the longer it runs on a single exposure, the more 'hot pixels' you'll get. These will go away when the sensor cools down again.

Noise reduction will take as long as the exposure is so you'll need to make sure that you have fresh batteries or an AC adapter for realy long exposures. If you don't want to use noise reduction, you can use a 'dark frame' where you take a picture with the lens cap on during the same session (this is more useful if you are taking a series of shorter shots rather than one single shot).

I've done a 2-3 minute test shot, but I haven't gotten around to do a real shoot yet. I've been waiting for the weather to warm up.
05-07-2008, 10:41 PM   #3
Veteran Member
pixelsaurus's Avatar

Join Date: Jul 2007
Location: Levin, NZ
Photos: Gallery | Albums
Posts: 783
Longest exposure I ever did was 4.5 hours. Then again I was using a Pentax MEF and Kodak Elitechrome 100 @ f/11. Noise was not a problem,nor was skyglow.
05-07-2008, 11:07 PM   #4
Senior Member




Join Date: Oct 2007
Posts: 241
I was recently at Joshua Tree NP doing this with my K10D, fully charged with the battery grip and the shutdown timer turned off ... no luck. As near as I can tell, the K10 just locked after about 4 minutes. I had to turn it off and on again to restore function. Interestingly, I got the picture - up to the point it locked. Of course it was seriously underexposed...

Anyways, multiple attempts ended in multiple failures.

Good luck! Let me know how it went and what you did to make it work.

Frank.

Ps. It wasn't the noise reduction feature - it was totally locked.

05-08-2008, 12:31 AM   #5
Veteran Member
PentaxPoke's Avatar

Join Date: Jan 2008
Location: Oklahoma
Posts: 1,411
I used to do this in film but never tried with a DSLR. Here's an idea but I don't know how it would work: Instead of shooting one long exposure shot that will result in sensor noise, would it be better to shoot many shots of shorter exposure (say 30 seconds each) and then digitally combine them?
05-08-2008, 05:04 AM   #6
Pentaxian
falconeye's Avatar

Join Date: Jan 2008
Location: Munich, Alps, Germany
Photos: Gallery
Posts: 6,863
QuoteOriginally posted by PentaxPoke Quote
I used to do this in film but never tried with a DSLR. Here's an idea but I don't know how it would work: Instead of shooting one long exposure shot that will result in sensor noise, would it be better to shoot many shots of shorter exposure (say 30 seconds each) and then digitally combine them?
This will work (not with a K20D though, as it wouldn't skip the dark frame exposures).

It's less the sensor noise in long exposures (won't be that bad after all). It is that you effectively shoot at much lower ISO if you combine images.
05-08-2008, 07:06 AM   #7
Veteran Member
jshurak's Avatar

Join Date: Jul 2007
Location: philadelphia
Posts: 627



This was a single 7.5 minute exposure with the K10D. f/13. I recall the battery dying after a number of shots like this. Probably 4 of 5 shots. Clicking on the picture should take you to the largest viewing size. if that doesn't work, here is the link
05-08-2008, 07:44 AM   #8
Senior Member




Join Date: Oct 2007
Location: Tallinn
Posts: 265
I once did 3 exposures of 15 min, 25 min. and 35min. almost in a row. With the camera in a bag with the lens cap on. Just wanted to see the results at ISO 1600. Battery was not empty afterwards. But of course maybe it was freshly recharged, don't remember anymore.

05-09-2008, 12:32 AM   #9
Forum Member




Join Date: May 2008
Location: Linköping, Sweden
Posts: 60
Alohadave: I didn´t know about the noise reduction and process time. I made some experiments with light painting and had the shutter opened for up to 5 mins on some pictures. I got very frustrated as I had to wait for every image getting processed and it almost took as long as the exposure. Do you mean it goes faster if you turn the noise reduction off?
05-09-2008, 01:25 AM   #10
Veteran Member
StarDust's Avatar

Join Date: Apr 2008
Location: Uppsala, Sweden
Posts: 400
Now, how would I go about getting longer exposures than the pre-programmed 30s? Have in mind a I don't have a remote nor a tripod but there are other ways of taking stable picture, a table for instance.
05-09-2008, 01:54 AM   #11
Pentaxian
falconeye's Avatar

Join Date: Jan 2008
Location: Munich, Alps, Germany
Photos: Gallery
Posts: 6,863
QuoteOriginally posted by KungKrille Quote
5 mins on some pictures. I got very frustrated as I had to wait for every image getting processed and it almost took as long as the exposure. Do you mean it goes faster if you turn the noise reduction off?
Yes, this is what he meant. If you turn it off, you must do the dark frame subtraction yourself in post processing (and manually take one dark frame shot). Google for "dark frame subtraction".

However, on the K20D, you can't turn it off anymore. (I think, 1/10s or so is the longest one can take w/o it, not sure, though).

This is why the star trail from many pictures won't work with a K20D -- except you make tens of thousand of images (only possible in mid quality JPEG).
05-09-2008, 05:04 AM   #12
Pentaxian




Join Date: Aug 2007
Photos: Gallery
Posts: 1,563
QuoteOriginally posted by joefru Quote
What's the longest bulb exposure anyone here's done? My last camera completely maxed out at 60s, and I want to do some star trails. I'm guessing that a single, ultra-long exposure (30 minutes or an hour) will harm the sensor. What's the longest that's safe? I've seen some good shots that were stacked 8-min exposures, but is the K10D different at all?

Thanks.
My longest photo exposure has been around 1 hour.
Done that 35 years ago, with a 2000mm telescope, with a small clock based mechanism to follow an object position in the sky.
A smaller telescope with a grid we used to correct the position of the telescope resulting from small temperature originated errors made by the following system.

We made photos from many different stellar and planetory objects and the moon.

Photos were made with both 6x6 cm glass plates and 35mm film cameras with home based film development and photo printing.

It was a great time and I learned my way around a dark room.

- Bert
05-10-2008, 02:41 AM   #13
Forum Member




Join Date: Apr 2008
Location: Hamburg
Posts: 70
QuoteOriginally posted by falconeye Quote
However, on the K20D, you can't turn it off anymore.
I'm still waiting for the f/w upgrade that will fix it ...
05-10-2008, 04:49 PM   #14
Senior Member
joefru's Avatar

Join Date: Mar 2008
Location: South Louisiana
Photos: Gallery
Posts: 210
Original Poster
QuoteOriginally posted by patrickhh Quote
I'm still waiting for the f/w upgrade that will fix it ...
Indeed. That was quite a stupid setting to remove. One of the big pluses for Pentax is that their cameras are very customizable. Yet you say, "No, dark frame subtraction is REQUIRED."

What?
05-11-2008, 03:45 AM   #15
Forum Member




Join Date: Apr 2008
Location: Hamburg
Posts: 70
QuoteOriginally posted by joefru Quote
Indeed. That was quite a stupid setting to remove. One of the big pluses for Pentax is that their cameras are very customizable. Yet you say, "No, dark frame subtraction is REQUIRED."

What?
Yes, very stupid.
Even more so if you think of hotpixels being easily removable with software.
(Lightroom maps them away by default, for example)

I hope that Pentax will address this issue in the next f/w upgrade.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, dslr, exposure, exposures, photography, star, star trails, trails
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Night Star Trails TOUGEFC Post Your Photos! 2 06-14-2010 04:30 AM
Any examples of long exposures or star trails from K-x? ambienthousewife Pentax DSLR Discussion 8 01-20-2010 12:18 PM
Night Star Trails builttospill Post Your Photos! 1 12-08-2009 08:58 AM
Star Trails from my Window navcom Post Your Photos! 21 01-27-2009 12:08 AM
Star Trails bdann Post Your Photos! 2 02-12-2008 02:14 PM



All times are GMT -7. The time now is 10:30 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top