Equivilant Exposure Help
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  1. #1
    Join Date
    Nov 2008
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    Meridian, Idaho
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    157

    Default Equivilant Exposure Help

    I really need help with my Equivilent exposures. I need them explained in a you're a dummy mode. I can do them all day long on my camera but on paper, I'm an utter failure at it.

    Does anyone have a link to something that explains it in bare basics? I have the London and Upton Book, plus several study guides but for me its like listening to the teacher on Charlie Brown. Wah Wah Wah.

    If someone is willing to skype and help this dunce out that works for me too. Help, Please!

  2. #2
    Join Date
    Mar 2009
    Location
    Port Huron, Michigan
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    1,105

    Default Re: Equivilant Exposure Help

    Jill, this is definitely one I struggled with on the exam. Honestly, I was annoyed that instead of your ISO, shutter and fstop going up or down equal stops the answers had your ISO going up 4, shutter down 2 and fstop down 1 ( I know my calculations aren't correct here, but you get the idea). I know the purpose of the question being that way, but I was still annoyed

    Steff suggested drawing and studying your ISO, shutter and fstop charts and I agree. I didn't do any of those for my test and spent a lot of time analyzing those questions.

    I was surprised at the amount of math required on the exam
    Amy Feick CPP

  3. #3
    Join Date
    Nov 2008
    Location
    Meridian, Idaho
    Posts
    157

    Default Re: Equivilant Exposure Help

    I have the charts, and I've drawn them on the times I've tested. I just realized I'd been doing my ISO's backwards.

    This test has done a good job of making feel like I don't have a freaking clue.....

  4. #4
    Join Date
    Feb 2008
    Location
    Standale, Michigan
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    Default Re: Equivilant Exposure Help

    Jill - hang in there! Sometimes you will discover that things have come naturally to you while you are doing it, but don't seem to make sense when you put them on paper. Just keep plugging away - you can do it!
    Angela Lawson CPP
    Michigan CPP Liason
    AGL Photography
    Where Life + Art = Memories Forever
    http://www.aglphotography.net



  5. #5
    Join Date
    Oct 2005
    Location
    Hudson, NH
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    6,047

    Default Re: Equivilant Exposure Help

    The fundamental issue you have to understand is that equivalent exposure is about comparing two exposures and accounting for the differences in stops for each factor (shutter speed, aperture, ISO) that contributes to the final exposure.

    Here's an example question. Is 1/200, f5.6, ISO 200 equivalent to 1/100, f8, ISO 100?

    consider this exposure as your baseline: 1/100, f8, ISO 100

    compare each factor individually.
    shutter speed at 1/200 = -1 (stops)
    aperture at f5.6 = +1
    ISO 200 = +1
    Add them all together: = +1, so no, it's not an equivalent. If I were showing you on a piece of paper, I'd be putting the +1 or -1 directly over each factor, and adding up to the right. If the sum is zero, then the exposure is equivalent.

    Let's do another. What shutter speed makes the equivalent exposure of 1/500, f4, ISO 200 if aperture is f5.6 and ISO is 100?

    aperture of f5.6 is -1; ISO of 100 is -1. This makes -2. So our shutter speed needs to be +2, or two stops greater than 1/500. +2 stops of shutter speed = 4X the shutter speed. 4/500 = 1/125, so the answer is 1/125.

    So the bottom line is you need to know that halving the shutter speed (e.g. from 1/500 to 1/1000) reduces the exposure by one stop, and doubling the shutter speed (e.g. from 1/500 to 1/250) increases the exposure by one stop. Don't get confused; remember that shutter speed is fractions of a second. The smaller the fraction, the shorter the duration, and the lower the exposure.

    Aperture works similarly. Open a stop ADDS one stop to the exposure (e.g. going from f5.6 to f4) whereas closing a stop (e.g. from f5.6 to f8) reduces exposure by one stop.

    ISO does the same thing. Increase ISO by a stop (e.g. 200 to 400) increases exposure by a stop, and decreasings ISO by a stop (e.g. 200 to 100) decreases exposure by a stop.

    With this knowledge in hand, answer this question:

    Which of the following is the equivalent exposure to 1/200, f11, ISO 800?

    A) 1/400, f8, ISO 400
    B) 1/400, f16, ISO 800
    C) 1/200, f8, ISO 1600
    D) 1/800, f8, ISO 1600
    E) 1/100, f16, ISO 400
    Mark Levesque, CPP, M. Photog., Cr. Photog, A.C. Ph., CPP Liaison, PPCC Judge

  6. #6
    Join Date
    Nov 2008
    Location
    Meridian, Idaho
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    Default Re: Equivilant Exposure Help

    I've seen the add and subtract thing before....

    You threw the ss200 in there and I don't have that on my handy chart.

    I'm going to take a break for a few hours, and come back to this. I've been on this for 2 hours, and my brain hurts.

  7. #7
    Join Date
    Feb 2008
    Location
    Standale, Michigan
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    Default Re: Equivilant Exposure Help

    Mark,

    Thanks for taking the time to type that all out. Hope you don't mind, but I'm going to borrow it to give to several of my candidates that are going to take the test in March. They have a study group starting, and I think this will be something that will make it easier for them to understand (than the book, at least).
    Angela Lawson CPP
    Michigan CPP Liason
    AGL Photography
    Where Life + Art = Memories Forever
    http://www.aglphotography.net



  8. #8
    Join Date
    Jan 2007
    Location
    New Orleans, LA.
    Posts
    3,572

    Default Re: Equivilant Exposure Help

    Quote Originally Posted by J_Davidson View Post
    You threw the ss200 in there and I don't have that on my handy chart.
    The reason you probably don't have 1/200 listed on your shutter speed is that it not a standard setting - it's about a third of a stop off of 1/250 which is a standard speed.
    Starting from a 1 second exposure - cut it in half repeatedly and you get
    1 sec
    1/2 sec
    1/4 sec
    1/8 sec
    1/16 sec - usually written as 1/15 - but you may find a few old lensboard mounted lenses with 1/16
    1/32 sec - written as 1/30
    1/64 sec - written as 1/60
    1/128 sec - written as 1/125
    1/256 sec - written as 1/250
    1/512 sec - written as 1/500
    1/1024 sec - written as 1/1000
    1/2028 sec - written as 1/2000
    Last edited by Rick_Massarini; 02-02-2012 at 08:48 PM.
    The best way to gain for yourself is to give OF yourself.
    - - - So get out there and volunteer for something ...


    Rick Massarini, M. Photog., Cr., CPP., F-PPLA
    PPLA Past President; 97th Recipient PPA Directors Award
    ASP SouthWest District Rep. & ASP Convention Booth Chairman


  9. #9
    Join Date
    Nov 2008
    Location
    Meridian, Idaho
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    Default Re: Equivilant Exposure Help

    Thanks Rick!

  10. #10
    Join Date
    Aug 2005
    Location
    Normal, Illinois
    Posts
    7,783

    Default Re: Equivilant Exposure Help

    This is so much easier for us old dudes who spent so much time looking at the full scales of apertures and shutter speeds on mechanical cameras and lenses.
    --Elephants can swim...
    ...and very gracefully.
    Knowing that,
    I do believe
    Anything is possible for me.

    Kirk Darling, CPP

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