Correct Answer for 3:1 Lighting Ratio - Page 2
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  1. #11
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    Also Remember

    your Main/Key light is always expessed as 1
    your Highlighs are always expressed to the left of the of the Main/Key
    which gives you an expression of 4:1 3:1 2:1 etc.
    and your shadows are expressed to the right of the Main/Key
    1:2 1:3 etc

    So if you have a Main ,Fill and Hightlight/Accents
    you might see this

    2:1:2 which is F16,F11,F8
    “The price of anything is the amount of life you exchange for it.” Henry David Thoreau

  2. #12

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    Quote Originally Posted by Michael Gan
    Deb!

    The reason it becomes 1.5 stops is because you have to take into account the amount of light from the main light that "spills" onto the fill light area. Although your mainlight is 8 and your fill is 5.6, there is about 1/2 stop added to your fill source thus reducing the light differential to 1.5.

    Michael
    That totally depends on your light placement. If the fill is directly behind you [d you are shooting head on to the subject] and your main is placed on one site then that would not be accurate. In that case your fill would be spilling on your main.

  3. #13
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    OK, come to think of it, the fill is adding the 1/2 stop to the main. either way, your adding light to the "dark side" which lowers the f stop ratio.

    Michael
    Michael Gan,M.Photog.Cr. CPP,
    Meritage House of Photography

    If your business depends on you, you don't own a business-you have a job. And it's the worst job in the world because you're working for a lunatic... You can't close it when you want to, because if it's closed you don't get paid. You can't leave it when you want to, because if you leave there's nobody there to do the work. You can't sell it when you want to, because who wants to buy a job?
    —Michael Gerber
    http://www.meritageonmain.blogspot.com

  4. #14

    Default Showing our Age

    Guys......We are all looking really bad here. I've been googling lighting ratios and it's time for all of us to go back to class. First of all the accepted value of an F stop is two units of light. So if your key light is F8 that equals 2 units of light. Now your fill at F5.6 equals 1 compared to F8. See where this is going? Main light set at 8 fill at 5.6 equals a 2:1 ratio. So for a three to one ratio add another unit or half an F stop of light to the main. That means F8 plus one half stop equals 3 in relationship to F5.6 which equals one a 3:1 ratio. Now this is what the London book says, so be it. Michael, I love you man, but 1.5 is more than 1 thus the difference between a highlight side that is 1.5 stops brighter than the shadow side is a HIGHER ratio than a highlight side that is 1 stop brighter than the shadow side. Derek, love you to man but your Key light is the number to the left of 1. The one is the fill. The Key or main is the 2, 3, 4 ,5 etc. and it represents units of light. Now I would argue that the spill Michael is talking about tweeks this formula by at least a half a stop as we all know from experience. So Even though I may not be creating a by the book 3;1 ratio with my one stop difference i bet it is more like a 2.5:1 ratio than a 2:1 as the book says and I think it looks better for general purpose portraiture than a ratio of almost 4:1 doing it by the book. Anyway Deb, and everyone else out there prepairing for the test, the answer is a 3:1 ratio is a difference of 1.5 stops between main light and fill. Sorry this took so long to get right. I'm putting my pointed hat back on now and sitting in the corner.

  5. #15
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    David, I feel the love, but there is a confusion between light ratio, and exposure. 5.6 is 1/2 the amount of light that is added to the entire scene. Your exposure will be higher than f8.

    Michael
    Michael Gan,M.Photog.Cr. CPP,
    Meritage House of Photography

    If your business depends on you, you don't own a business-you have a job. And it's the worst job in the world because you're working for a lunatic... You can't close it when you want to, because if it's closed you don't get paid. You can't leave it when you want to, because if you leave there's nobody there to do the work. You can't sell it when you want to, because who wants to buy a job?
    —Michael Gerber
    http://www.meritageonmain.blogspot.com

  6. #16
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    Quote Originally Posted by David A. Lottes
    ratio than a highlight side that is 1 stop brighter than the shadow side. Derek, love you to man but your Key light is the number to the left of 1. The one is the fill. The Key or main is the 2, 3, 4 ,5 etc. and it represents units of light. Now I would argue that the spill Michael is talking about tweeks this formula by at least a half a stop as we all know from experience. So Even though I may not be creating a by the book 3;1 ratio with my one stop difference i bet it is more like a 2.5:1 ratio than a 2:1 as the book says and I think it looks better for general purpose portraiture than a ratio of almost 4:1 doing it by the book. Anyway Deb, and everyone else out there prepairing for the test, the answer is a 3:1 ratio is a difference of 1.5 stops between main light and fill. Sorry this took so long to get right. I'm putting my pointed hat back on now and sitting in the corner.
    David

    I would have to disagree with your Google

    I just pull out my old books here and all say the same thing

    the Main Light is always 1. as to which way the light Spills that I'm not sure not sure????
    “The price of anything is the amount of life you exchange for it.” Henry David Thoreau

  7. #17
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    David

    Where did you find those results i've never heard that and would like to read it
    “The price of anything is the amount of life you exchange for it.” Henry David Thoreau

  8. #18
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    David BTW i'm willing to except I'm wrong on what the 1 is but I'd like to hear what and where it comes from
    “The price of anything is the amount of life you exchange for it.” Henry David Thoreau

  9. #19

    Default

    Here you go Derek

    http://www.vividlight.com/articles/1916.htm

    I read bunches of stuff but this one was the clearest to me. I think part of our problem here is we don't have the exact wording of the question. Does it ask how to set up your lights or how to meter your subject. Like Michael said there is a difference between metering of each light and the metering of the over all exposure. Anyway I hope you enjoy the link. It makes sense to me. I think?

    Sorry I didn't post this sooner, I had an evening consultation with a couple for a wedding next June. BOOKED EM on the new and and increased prices! Thats a good thing, I think?
    Last edited by David_A._Lottes; 09-07-2006 at 03:06 AM.

  10. #20
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    Default Cleared Up

    Here is what to understand for the test:

    The camera sees the fill light as the sole illumination of the shadows. Call that 1 unit of light. The key light--which we've adjusted to be twice as bright as the fill--illuminates the part of the face it strikes with 2 units of light.

    But from the viewpoint of the camera position, that 1 unit of fill light ALSO strikes the same areas visible to the camera as the key light does. So from the camera position, the highlights are getting 3 units of light while the shadows are getting 1.

    Going from 1 unit of light to two units of light is a one stop increase. But adding just one more unit of light is only a half stop increase above THAT. In order to make it a 2 stop increase, we'd have to have fully doubled the light a second time (2 units) not just add 1 more unit.

    1 unit + 1 unit = 1 stop increase.
    1 unit + 1 unit + 1 unit = 1.5 stop increase.
    1 unit + 1 unit + 2 units = 2 stop increase.

    Here is the diagram, so you can clearly see where a 2x difference in the lights equals a 1:3 ratio.

    You get a 1.5 stop difference if you meter incorrectly. If you turn the meter to the fill light with the dome extended, then do the same toward the main light, you will see a 1.5 stop difference. But the metering to determine the ratio should be done with the domes retracted (Sekonic) or with the flat diffuser (Minolta).
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    Last edited by KirkDarling; 09-07-2006 at 03:22 AM.
    --Elephants can swim...
    ...and very gracefully.
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    I do believe
    Anything is possible for me.

    Kirk Darling, CPP

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