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Thread: Bulb Exposure

  1. #41
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    Default Re: Bulb Exposure

    i know it's possible and I have done it myself before but there are many factors that contribute to the results. moon, street/building lighting (basically light pollution), and clouds that reflect lights from (light) polluted areas.

    According to Snoweagle, he did it in a pitch dark environment. further more I believe he shoots film. at 5 mins I believe reciprocity failure would have kicked in as mentioned by Isisaxon. But it's good to know that 5minutes would produce such results. It's good experience sharing.

    So back to the question, how to know the exposure time in bulb? I use digital, so I can afford to test. I do a 2 minute test with f/8 at ISO400 and work from there. Since my cam can only open for 30mins, I will just aim for a 30min exposure.. anything under or slightly over can be corrected with post processing later.

    If you look at singastro, there are some pictures that have showed night scenes turning into more like pre-dawn instead of 'day' pictures.
    “How fortunate for leaders that men do not think.” - Adolf Hitler

  2. #42
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    Default Re: Bulb Exposure

    Quote Originally Posted by blimmer
    you did a good job luring out the pros, high commendable
    i'm not a pro but just sharing some experience i have. I'm also a newbie
    “How fortunate for leaders that men do not think.” - Adolf Hitler

  3. #43

    Default Re: Bulb Exposure

    Quote Originally Posted by yanyewkay
    According to Snoweagle, he did it in a pitch dark environment. further more I believe he shoots film. at 5 mins I believe reciprocity failure would have kicked in as mentioned by Isisaxon. But it's good to know that 5minutes would produce such results. It's good experience sharing.

    So back to the question, how to know the exposure time in bulb? I use digital, so I can afford to test. I do a 2 minute test with f/8 at ISO400 and work from there. Since my cam can only open for 30mins, I will just aim for a 30min exposure.. anything under or slightly over can be corrected with post processing later.
    About 5 years ago, I was in Provence. I look out from the balcony of my apartment, and saw a beautiful barn lit by lights from a few lamposts.

    I was using Tri-X. Could not remember the rating. Somehow my meter could not give me the proper readings. There was no "instant" review then.

    The scene was certainly not "pitch-dark". I could see the door and the window sills.

    I took several exposures, including up to one with one hour! The whole excercise took several hours.

    But all the exposures were "under" and non-printable.

  4. #44

    Default Re: Bulb Exposure

    Quote Originally Posted by yanyewkay
    i know it's possible and I have done it myself before but there are many factors that contribute to the results. moon, street/building lighting (basically light pollution), and clouds that reflect lights from (light) polluted areas.

    According to Snoweagle, he did it in a pitch dark environment. further more I believe he shoots film. at 5 mins I believe reciprocity failure would have kicked in as mentioned by Isisaxon. But it's good to know that 5minutes would produce such results. It's good experience sharing.

    So back to the question, how to know the exposure time in bulb? I use digital, so I can afford to test. I do a 2 minute test with f/8 at ISO400 and work from there. Since my cam can only open for 30mins, I will just aim for a 30min exposure.. anything under or slightly over can be corrected with post processing later.

    If you look at singastro, there are some pictures that have showed night scenes turning into more like pre-dawn instead of 'day' pictures.
    Yeah.. If they become too bright, you will lose all the stars. For the exposure, you can use a stopwatch.

  5. #45
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    Default Re: Bulb Exposure

    Quote Originally Posted by student
    About 5 years ago, I was in Provence. I look out from the balcony of my apartment, and saw a beautiful barn lit by lights from a few lamposts.

    I was using Tri-X. Could not remember the rating. Somehow my meter could not give me the proper readings. There was no "instant" review then.

    The scene was certainly not "pitch-dark". I could see the door and the window sills.

    I took several exposures, including up to one with one hour! The whole excercise took several hours.

    But all the exposures were "under" and non-printable.
    cannot dodge?
    “How fortunate for leaders that men do not think.” - Adolf Hitler

  6. #46

    Default Re: Bulb Exposure

    Quote Originally Posted by Rmh159
    Haha ok so even after all of this discussion (although extremely useful and interesting) I'm not sure that my original question was answered.

    When you go outside and look at a scene how do you know how long to expose it? Someone suggested a meter but my guess is that with Bulb shots you wouldn't use one (unless a meter would truly say '8 Hours').

    From your discussion it sounds as if you can't really over-expose a Bulb shot unless a light source comes into frame but what makes you look at a scene and say "30 minutes will work" or "I think I'll leave it exposed until the batteries die".

    Maybe I'm having trouble understanding this because I'm using daytime photography as a reference where the slightest variation in shutter speeds could ruin the shot. Any more ideas?

    Thanks for the feedback and posts... VERY interesting to just sit back and observe.
    You just have to remember. Every stop is doubling the exposure time. For shooting at 1/125, you get one more stop if you double the time ->1/60, and lose a stop if you half the time, 1/500. For long exposures, eg 1 min exposure, double the time is 2 mins, half the time is 30s. a couple of seconds won't make much of a difference. For 1 hour exposure, half the time is 30 mins, double the time is 2h, a few minutes won't make that much of a difference. Get the point?

  7. #47
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    Default Re: Bulb Exposure

    BULB mode or long exposure on DSLR is not advisable if it is more that 30 mins. tThe wait for NR process will kill you. The last NDP was a really good experience for me with the 1st time using Digital. By the time the NR is over, I had missed more than 10 other oppotunities.

    I think it also fries the CCD or CMOS sensors more than if you have taken 100 decent normal shots. As far as I experienced, I have left my Nikon DSLR on B overnight, it still stayed opened till the batts were flat. No batts also mean no pix recorded. Hee Hee

  8. #48
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    Default Re: Bulb Exposure

    your model can't turn off the NR and do black frame subtraction after that? which model were you using that allowed you to do continuous exposure >30mins?
    “How fortunate for leaders that men do not think.” - Adolf Hitler

  9. #49
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    Default Re: Bulb Exposure

    Different ones. D70, DCS14n, D100, D1x. It just that I need the NR as the client require good Q pix for the commemorative mag.
    Last edited by tommon; 1st March 2006 at 07:22 PM.

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