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Thread: long exposures. how?

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    Default long exposures. how?

    hey guy/girls.
    i hav seen sum pix in the night shots forums.
    they expose the pix for like 500 over secs to make a super dark area bright.
    how they know the timing to get a ok exposure? not under or over expose?

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    Default Re: long exposures. how?

    estimate lor...

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    Default Re: long exposures. how?

    long exposure usually off by few seconds won't matter much..
    eat. drink. shoot

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    Default Re: long exposures. how?

    Agak-agak.

    Film is best for long exposure. try long exposure with dSLR, and you will see hot-pixels come out.

    Regards,
    Arto.

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    Default Re: long exposures. how?

    Yah, I have the same question too....read book that says the formular Exposure=Aperture X Shutter Speed is only applicable to shorter shuter speed.....if like <10 sec this formular is not accurate liao....so, need to agar-agar...

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    Default Re: long exposures. how?

    Quote Originally Posted by noob117 View Post
    hey guy/girls.
    i hav seen sum pix in the night shots forums.
    they expose the pix for like 500 over secs to make a super dark area bright.
    how they know the timing to get a ok exposure? not under or over expose?
    Well I don't know about the rest.. for me I calculate the amt of light..

    if ISO 1600, f2.8 = 10 seconds to get proper exposure..
    1600 => 800 => 400 => 200 => 100 = 4 stops, so take 10 x 2 x 2 x 2 x 2
    then ISO 100 F2.8 = 160 seconds..
    F2.8 => F4 => F5.6 => F8 = 3 stops, so take 160 x 2 x 2 x 2
    then ISO 100 F8 = 1280 seconds needed for an exposure..

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    Default Re: long exposures. how?

    for film u need to take care of reciprocal failure....
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    Default Re: long exposures. how?

    my explaination is like this..i think the stop system still plays a part..
    at 30sec to increase 1 stop its 1min..and for 1min to increase 1 stop its 2min..and for 2min to increase 1 stop its 4min..so on and so forth..hence as the longer ur exposure becomes, the accuracy of seconds becomes insignificant..just my 2cents..
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    Default Re: long exposures. how?

    Quote Originally Posted by unseen View Post
    Well I don't know about the rest.. for me I calculate the amt of light..

    if ISO 1600, f2.8 = 10 seconds to get proper exposure..
    1600 => 800 => 400 => 200 => 100 = 4 stops, so take 10 x 2 x 2 x 2 x 2
    then ISO 100 F2.8 = 160 seconds..
    F2.8 => F4 => F5.6 => F8 = 3 stops, so take 160 x 2 x 2 x 2
    then ISO 100 F8 = 1280 seconds needed for an exposure..
    this is nice way of calculating too ..will try it out
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    Default Re: long exposures. how?

    I think TS is asking how you know the initial setting, like you need ISO1600 f2.8 form 10s in the first place?

    By the way, when time is >10s (IIRC), your formular is not correct....this is what I read from a book.

    Quote Originally Posted by unseen View Post
    Well I don't know about the rest.. for me I calculate the amt of light..

    if ISO 1600, f2.8 = 10 seconds to get proper exposure..
    1600 => 800 => 400 => 200 => 100 = 4 stops, so take 10 x 2 x 2 x 2 x 2
    then ISO 100 F2.8 = 160 seconds..
    F2.8 => F4 => F5.6 => F8 = 3 stops, so take 160 x 2 x 2 x 2
    then ISO 100 F8 = 1280 seconds needed for an exposure..

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    Default Re: long exposures. how?

    Yah, it's call the reciprocal failure that makes the Exposure=timexaperture inaccurate...

    Quote Originally Posted by dreamerz View Post
    for film u need to take care of reciprocal failure....
    Sorry, I have finally got the time to rectify my statement. the formular is only accurate from 1/1000s to 1s. So anything more than 1s shutter speed is not accurate (but I think it wont affect many of us lah). And it is call Reciprocity Failure, not Reciprocal Failure.

    Check out this site on how to compensate for the difference.

    However, I am not sure if it affects digi cam....Canon says it doesn't affect their cam...
    Last edited by lastboltnut; 20th October 2006 at 05:20 PM.

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    Default Re: long exposures. how?

    wah so leceh.
    will it like spoit the shutter if its open for too long?

  13. #13

    Default Re: long exposures. how?

    Quote Originally Posted by lastboltnut View Post
    Yah, it's call the reciprocal failure that makes the Exposure=timexaperture inaccurate...



    Sorry, I have finally got the time to rectify my statement. the formular is only accurate from 1/1000s to 1s. So anything more than 1s shutter speed is not accurate (but I think it wont affect many of us lah). And it is call Reciprocity Failure, not Reciprocal Failure.

    Check out this site on how to compensate for the difference.

    However, I am not sure if it affects digi cam....Canon says it doesn't affect their cam...
    oops...remember the term salar...

    digital is nt affected as much as film...
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  14. #14

    Default Re: long exposures. how?

    Quote Originally Posted by noob117 View Post
    wah so leceh.
    will it like spoit the shutter if its open for too long?
    if tat the case...alot of camera spoil liao...
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    Default Re: long exposures. how?

    ic ic
    any ideas on any thing to start wif?
    i can onli use max of 30secs wif timer.
    i dun have remote release. i hold then later cam shake.

  16. #16

    Default Re: long exposures. how?

    Quote Originally Posted by noob117 View Post
    ic ic
    any ideas on any thing to start wif?
    i can onli use max of 30secs wif timer.
    i dun have remote release. i hold then later cam shake.
    the only thing is get a cable release...set to bulb
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    Default Re: long exposures. how?

    may i know how much is a reasonalble priced one for a canno 350d?

  18. #18

    Default Re: long exposures. how?

    Quote Originally Posted by noob117 View Post
    may i know how much is a reasonalble priced one for a canno 350d?
    new ard 1.2K
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    Default Re: long exposures. how?

    Quote Originally Posted by dreamerz View Post
    new ard 1.2K
    eh i think he meant the remote cable

  20. #20

    Default Re: long exposures. how?

    Quote Originally Posted by ExplorerZ View Post
    eh i think he meant the remote cable
    oops...misread it...

    3rd party cable release can liao lar...ard 20..
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