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Thread: slow shutter speeds and exposure.

  1. #1

    Default slow shutter speeds and exposure.

    hello everyone!

    I am wondering...
    how do people take long exposures (like, really long... 2 mins, 15 mins etc...) knowing when to close the shutter? been seeing some perfectly exposed pictures which one had a shutter speed of 384 secs.
    so maybe someone could teach or enlighten me?

  2. #2
    Member gymak90's Avatar
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    Default Re: slow shutter speeds and exposure.

    Quote Originally Posted by HTCahHTC View Post
    hello everyone!

    I am wondering...
    how do people take long exposures (like, really long... 2 mins, 15 mins etc...) knowing when to close the shutter? been seeing some perfectly exposed pictures which one had a shutter speed of 384 secs.
    so maybe someone could teach or enlighten me?
    Bulb mode. With/without shutter release cable.
    The best things in life are free.

  3. #3

    Default Re: slow shutter speeds and exposure.

    Quote Originally Posted by gymak90 View Post
    Bulb mode. With/without shutter release cable.
    yup yup, this i know.
    was trying to ask, how do they know whether the pic is undexposed/overexposed?

    is like, i'm shooting in Bulb for already 2 mins, how do i know whether i've exposed enough/too much?

  4. #4
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    Default Re: slow shutter speeds and exposure.

    the oldest way, trial, error and speculation
    Sony Alpha 700 hobbyist

  5. #5
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    Default Re: slow shutter speeds and exposure.

    1. Set mode to Aperture Priority.
    2. Set ISO to highest available, example 1600.
    3. Set aperture to any choosing, example f5.6.
    4. Note shutter speed, example 10s
    5. Do mental sums.
    - if ISO=100, then shutter speed=160s (1600 --- 10s, 800 --- 20s, 400 --- 40s, 200 --- 80s, 100 --- 160s)
    and
    - when aperture=f8, then shutter speed=320s (f5.6 --- 160s, f8 --- 320s)
    6. Enter final settings into camera, ISO 100 F8 320s

    Points to note:
    1. At long time exposures, there is little to no difference in mere seconds. A shutter speed of 320s and 325s have little bearing compared to 5s and 10s.
    2. It is vital you understand the relation of 1stop=2xAmount of light
    Last edited by foxtwo; 18th December 2008 at 10:26 PM.

  6. #6

    Default Re: slow shutter speeds and exposure.

    Quote Originally Posted by HTCahHTC View Post
    yup yup, this i know.
    was trying to ask, how do they know whether the pic is undexposed/overexposed?

    is like, i'm shooting in Bulb for already 2 mins, how do i know whether i've exposed enough/too much?
    not that hard.

    shoot wide open, get the exposure, then use stops and all that to adjust accordingly.

    if you are talking about extremely, extremely long exposure then i can't help you there. it's all up to guestimation and experience. i suppose for things like star trails it doesn't really matter, since you will be at a location where you will find it hardpressed to end up overexposing. the only problem is underexposure.

  7. #7
    Member gymak90's Avatar
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    Default Re: slow shutter speeds and exposure.

    For me, I do trial and error.

    I don't think a light meter will work at night.

    So start off with a rough shot and get some values. Then compensate accordingly by the number of stops.
    Basically at night, it is near impossible to get an overexposed shots, except when you have lights. Thus again, adjust accordingly until you're satisfied.
    Last edited by gymak90; 18th December 2008 at 11:16 PM.
    The best things in life are free.

  8. #8
    Moderator catchlights's Avatar
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    Default Re: slow shutter speeds and exposure.

    for digital, unlike film, you need not to bother about the reciprocity failure.
    Shoot to Live, Live to Shoot
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  9. #9

    Default Re: slow shutter speeds and exposure.

    hey.
    thanks for all the replies and inputs.
    will try out someday.
    once again, thanks!

  10. #10

    Default Re: slow shutter speeds and exposure.

    for long exposure, there is no need to be very accurate.

    eg, 1 sec and 2 sec is ONE stop difference.

    5 min (300sec) and 10min (600sec) is also ONE stop difference.

    so, its perfectly alright to plus minus 1 or 2 dozen seconds, and end up w essentially the same exposure.

  11. #11

    Default Re: slow shutter speeds and exposure.

    Quote Originally Posted by attap seed View Post
    for long exposure, there is no need to be very accurate.

    eg, 1 sec and 2 sec is ONE stop difference.

    5 min (300sec) and 10min (600sec) is also ONE stop difference.

    so, its perfectly alright to plus minus 1 or 2 dozen seconds, and end up w essentially the same exposure.
    really?
    didn't know that. thanks dude.

  12. #12

    Default Re: slow shutter speeds and exposure.

    Quote Originally Posted by HTCahHTC View Post
    really?
    didn't know that. thanks dude.
    every stop approximately double

    so for example, 60 seconds is one stop more than 30. etc etc etc

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