bulb setting~ how do you know?

Discussion in 'Photography Beginners' Forum' started by SimplyMo, Jul 29, 2008.

  1. SimplyMo

    SimplyMo TPF Noob!

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    when using the Bulb setting for shutter speed, how do you what length of time to use? :scratch:.......
    by using a hand held meter? or just guess? do a couple test exposures?


     
  2. nynfortoo

    nynfortoo TPF Noob!

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    You could meter to get the right exposure with a non-BULB shutter speed, then step down the aperture and/or ISO to get the right settings for your exposure.

    Stops are a doubling/halving of light, so it shouldn't be too difficult.

    edit: use a stopwatch or something to actually measure the time. I should learn to read.
     
  3. Overread

    Overread has a hat around here somewhere Staff Member Supporting Member

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    I have used bulb for waterfalls for that blurred water effect at rather a late hour and for that I was very much just using it at random and seeing what effect different speeds would yeald and then reshooting after.
    The other use of bulb I have seen is where you use it to shoot lightning or fireworks where you leave the shutter open (pointing at a very dark sky, not something for town work) and then wait for the flash of light - then quickly close the shutter. A cover is also handy to hold infront of the lens during gaps (mostly for firework shots as then you can decide to have the rocket in the shot or not-
     
  4. Helen B

    Helen B TPF Noob!

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    You may be able to extrapolate from a wide aperture reading, if the light level is within your camera meter's sensitivity range. For example, if 2 s is the longest shutter speed the camera will do, and you get a reading of 2 s at f/1.4, you could calculate 32 s at f/5.6 in your head. If using film, you may then have to account for reciprocity departure (aka reciprocity failure).

    Edit: I see that nynfortoo wrote the same thing as I was typing this.

    If your camera meter is struggling to read because of low light leves, try taking a reading from a white card or other white object and open up two stops. This gives an effective two-stop increase in the sensitivity of your meter.

    Best,
    Helen
     
  5. nynfortoo

    nynfortoo TPF Noob!

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    Your answer was far more elegant and easy to understand though!
     

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