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Thread: need help in long exposure calculation

  1. #1

    Default need help in long exposure calculation

    Hi there, I just come across with bulb mode for long exposure photography. Normally I do a exposure with 15sec only (cuz that what my current camera allow me to do – fuji S5200 is without bulb mode).

    I know is stupid to ask how to calculating the shutter time require fro bulb mode, where my camera dun even have the bulb mode function.

    But anyway, here goes…



    when aperture f-number = Require Shutter Time
    2.8 =15 sec
    4 =30 sec
    4.6 =60 sec @ 1 min
    8 =120 sec @ 2 min
    11 =240 sec @ 4 min
    16 =480 sec @ 8 min







    If the correct exposure is f 2.8 at 15 sec.
    then the other “on-going estimation” are calculate like this??
    thank in advance
    Last edited by likimikuku; 28th January 2008 at 04:13 PM.

  2. #2

    Default Re: need help in long exposure calculation

    any1??

  3. #3
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    Default Re: need help in long exposure calculation

    yes.

  4. #4
    Moderator ziploc's Avatar
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    Default Re: need help in long exposure calculation

    Quote Originally Posted by likimikuku View Post
    when aperture f-number = Require Shutter Time
    2.8 =15 sec
    4 =30 sec
    4.6 =60 sec @ 1 min
    8 =120 sec @ 2 min
    11 =240 sec @ 4 min
    16 =480 sec @ 8 min
    Don't understand what you're trying to say here. Why would aperture = shutter time?

  5. #5

    Default Re: need help in long exposure calculation

    thank ...
    got it..

  6. #6
    Senior Member sammy888's Avatar
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    Default Re: need help in long exposure calculation

    Quote Originally Posted by likimikuku View Post
    Hi there, I just come across with bulb mode for long exposure photography. Normally I do a exposure with 15sec only (cuz that what my current camera allow me to do – fuji S5200 is without bulb mode).

    I know is stupid to ask how to calculating the shutter time require fro bulb mode, where my camera dun even have the bulb mode function.

    But anyway, here goes…



    when aperture f-number = Require Shutter Time
    2.8 =15 sec
    4 =30 sec
    4.6 =60 sec @ 1 min
    8 =120 sec @ 2 min
    11 =240 sec @ 4 min
    16 =480 sec @ 8 min

    If the correct exposure is f 2.8 at 15 sec.
    then the other “on-going estimation” are calculate like this??
    thank in advance
    There is only one way to break this to you and that is to tell you like it is. Yup you got it.. It is stupid to ask something like that.

    Firstly you only have a PnS that only let you control a speed of up to only 15 secs. So why do you need to have a formula to give you difference shutter speed for various aperture setting.

    And who say there is even a formula for long exposure to begin with? Especial when in BULD MODE. Some DSLR OR SLR give you shutter speed setting like 5sec, 15sec, 30sec or 1 minute..etc not becasue there is a formula to it....it is just for OUR conveinences.

    There is nothing to stop me from using 5 second or 30 second with the same aperture of say f8 if I felt like doing so and if the exposure works for it ....or might not depending on what kind of scene I am attempting to shoot. How can there sensibly be a fixed formula table for setting speed to aperture when you are now working in a night scene where the percentage of dark to light areas are so difference or isolated or worst...have more dark then brightly lit parts? ...so how can even a camera with advance exposure meter be able to creatively choose one of those setting that produces the BEST exposure for your shot? In night shoot, the same formulas you have for shooting in a brightly lit place or day time in the outdoor no longer apply.

    At higher shutter speed when you are dealing with day time shooting or flash photographer...there really is no fixed formula too if you want to know. What your auto exposure in your camera gives you is still estimated but of course in a lighted scene situation, film and digital film sensitivity has been made to handle those situation better to helping you get ideal exposed shot ..."most of the time". But that is only a guide. The auto meter in your camera or you'r eye ( and lack of experince) could still get the photo exposure wrong or not fit the scene your mind's eye imagine it.

    This is where experience and trial and error comes into play. And since you have no camera with shutter setting slower then 15 seconds to let you experiment shutter speed versus aperture setting...then what you asked for is mute sorry to say. With no proper gear to experiment with..what anyone tells you here is of little use to you.
    Last edited by sammy888; 28th January 2008 at 04:56 PM.

  7. #7

    Default Re: need help in long exposure calculation

    thank for the guide..
    guess i am too much for asking it..where i dun hav a dslr or a bulb mode in my cam..

  8. #8

    Default Re: need help in long exposure calculation

    Quote Originally Posted by ziploc View Post
    Don't understand what you're trying to say here. Why would aperture = shutter time?
    erm.. what i mean is:
    if f 2.8 at 15sec are the right shutter for correct exposure..
    then when i incress the F number.. does the incress of the shutter speed are right guide??

  9. #9
    Moderator ziploc's Avatar
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    Default Re: need help in long exposure calculation

    Hi likimikuku,

    To understand how to calculate this, you'll need to get a basic understanding of a "stop". Each stop will allow half or double the light entering the camera. 1 stop = 1 EV. So e.g, one stop down from f/5.6 is f/8, and at f/8 the light is half of that at f/5.6. Same goes for shutter speed. From 1/125s to 1/250s is 1 stop down and allows only half the light in (naturally since you are cutting the time by half).

    The following are 1 stop stepping for aperture and shutter speed:
    Aperture: 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, etc.
    Shutter speed: .. 1/15, 1/30, 1/60, 1/125, 1/250 etc.
    Each is a stop difference from the previous or next.

    Now let's say your camera meter tells you that the current exposure is f/5.6 at 1/125s. To maintain the same exposure, you can for e.g. change setting to f/8 at 1/60s. Why? In terms of aperture, you have reduced 1 stop of light, so to compensate you'll need to have 1 stop more in shutter speed, so that the exposure remains the same.

    So in your case, if the meter says the exposure is f/2.8, 15 secs, then you're correct to say that the following will all give you the same exposure:
    f/2.8, 15 sec
    f/4, 30 sec
    f/5.6, 60 sec
    f/8, 120 sec
    f/11, 240 sec
    f/16, 480 sec

    Hope that helps.

  10. #10
    Senior Member sammy888's Avatar
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    Default Re: need help in long exposure calculation

    Quote Originally Posted by likimikuku View Post
    erm.. what i mean is:
    if f 2.8 at 15sec are the right shutter for correct exposure..
    then when i incress the F number.. does the incress of the shutter speed are right guide??
    As your aperture start to get bigger for example F4.5 then your shutter speed should be longer not shorter. But how much more or less does not alway happen in a constant manner that is all I will say. It's just a guide as I menioned in my earlier post

    You have no DSLR or a PnS with that capablilty thus there is no way you are going to really know what I mean or anyone else for that matter.

    You want to learn this at your own time...get a book on basic photography 101. Study up on exposure in film and digital film to learn more about it. That is if you really want to learn about it. And if you really really want to learn to apply it ..buy a camera that allows you to experiment it. If not whatever anyone can tell you or write long essay on it to explain will mean nothing to you after which at this time. In theory it sound right to calculate exposure the way you did but in the real world it does not. It is not as simple as just shutter speed and aperture...set in various combination can effect how your photo turns out.
    Last edited by sammy888; 28th January 2008 at 05:23 PM.

  11. #11
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    Default Re: need help in long exposure calculation

    Quote Originally Posted by likimikuku View Post
    Hi there, I just come across with bulb mode for long exposure photography. Normally I do a exposure with 15sec only (cuz that what my current camera allow me to do – fuji S5200 is without bulb mode).

    I know is stupid to ask how to calculating the shutter time require fro bulb mode, where my camera dun even have the bulb mode function.

    But anyway, here goes…



    when aperture f-number = Require Shutter Time
    2.8 =15 sec
    4 =30 sec
    4.6 =60 sec @ 1 min
    8 =120 sec @ 2 min
    11 =240 sec @ 4 min
    16 =480 sec @ 8 min







    If the correct exposure is f 2.8 at 15 sec.
    then the other “on-going estimation” are calculate like this??
    thank in advance
    erm, btw, its 5.6 for the above bold part.


    like wad u said, lets say a correct exposure requires f/2.8, 15sec, constant ISO.

    apertures: f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32 (all these are 1 stop away)

    shutter speeds in sec: 1, 2, 4, 8, 15, 30, 60 (all these are 1 stop away)

    if u drop the aperture down 1 stop, shutter speed has to drop 1 stop to allow more light to enter.
    Last edited by Fragnatic; 28th January 2008 at 05:24 PM.
    EOS 6D | GH4 | LX100 | HERO4

  12. #12
    Moderator ziploc's Avatar
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    Default Re: need help in long exposure calculation

    Hello sammy888,

    I think such remark is uncalled for. He might not have the equipment but that doesn't mean he is not allowed to learn more from other forumers that are willing to teach him.

  13. #13

    Default Re: need help in long exposure calculation

    Thank bro ziploc and Fragnatic.. now i hav better understanding of it..

    will try it, when i got my dslr...

    for now, i will keep on reading.. as i really into this Photography stuff...

  14. #14
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    Default Re: need help in long exposure calculation

    Quote Originally Posted by likimikuku View Post
    Thank bro ziploc and Fragnatic.. now i hav better understanding of it..

    will try it, when i got my dslr...

    for now, i will keep on reading.. as i really into this Photography stuff...
    yep. u can read this guide (the whole thing): http://forums.clubsnap.com/showthread.php?t=245883
    EOS 6D | GH4 | LX100 | HERO4

  15. #15

    Default Re: need help in long exposure calculation

    wow.. that is a some thread..
    guess i hav to print it out to study..
    thank mate

  16. #16
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    Default Re: need help in long exposure calculation

    Quote Originally Posted by likimikuku View Post
    wow.. that is a some thread..
    guess i hav to print it out to study..
    thank mate
    lol... happy reading..

    no need print out la. TS is constantly editing and adding in new stuff...
    and some sections are not completed.
    EOS 6D | GH4 | LX100 | HERO4

  17. #17
    Senior Member sammy888's Avatar
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    Default Re: need help in long exposure calculation

    Quote Originally Posted by ziploc View Post
    Hello sammy888,

    I think such remark is uncalled for. He might not have the equipment but that doesn't mean he is not allowed to learn more from other forumers that are willing to teach him.
    I apologise if I sounded harsh with him. And I can understand where you are coming from and maybe your approach it the preferred way. Might be my approach is not correct but it is never my intention to discourage anyone if someone really wants to learn and make the effect. If he happens to be one of those who sincerely wants help, I have no problem with that. I have never ever discourage nor make a nuisance of myself to not help if I can. If I misread his sincerity I can accept that.,,I will adjust my tone accordingly.

  18. #18

    Default Re: need help in long exposure calculation

    Quote Originally Posted by sammy888 View Post
    I apologise if I sounded harsh with him. And I can understand where you are coming from and maybe your approach it the preferred way. Might be my approach is not correct but it is never my intention to discourage anyone if someone really wants to learn and make the effect. If he happens to be one of those who sincerely wants help, I have no problem with that. I have never ever discourage nor make a nuisance of myself to not help if I can. If I misread his sincerity I can accept that.,,I will adjust my tone accordingly.
    hey dude, no worry..
    u do got ur point (where i do really need to learn and apply)..
    i do hav plan to buy a dslr, that y i am reading and asking..

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