Correct Answer for 3:1 Lighting Ratio - Page 3
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  1. #21
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    Quote Originally Posted by Derek Alvarez
    Ratios



    here is a way to look at it


    1 ..2.. 4.. 8.. 16.. 32.. 64.......


    each number doubles these number are your ratios

    1:1 ... 1:2 ...1:4 ...1:8 etc

    so let put this to an fstop

    a 1:1 is f11/f11
    1:2 is f11/f8
    1:4 is f11/f5.6


    now lets add 1/2 stops

    go back to the ratio chart
    1 ..2 ..4 ok
    here is how it will look

    1..2..3*..4..6*..8..12*..16........

    the *number is the 1/2stop ratio

    so a 1:3 ratio is 1 and 1 1/2
    or F11/F 6.7

    does that help
    Deb
    Ok this Portion of my post is correct


    However the jury is still out on this next part

    All of the Portrait lighting Books I have show
    the Main/Key as 1

    which is always the way I read the Ratio



    "

    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



    There is very little Info on this part of the Ratios listed on the internet
    but there is a conflict
    Last edited by Derek_Alvarez; 09-07-2006 at 11:59 AM.
    “The price of anything is the amount of life you exchange for it.” Henry David Thoreau

  2. #22

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    Thanks for the diagram Kirk
    If you look at Kirk's diagram it says 3:1 ratio. The 3 expresses the value of the Main light and is to the left of the 1. Now I'm not sure about the dome thing. A human face is in a dome shape so I would think that is what you would want to use to meter it. Not a flat 2 dimensional diffuser. I would think the only time to use the flat diffuser would be for a reflective reading or an incedent reading on a flat surface. But that's another can of worms.

    Deb I would really love it if you could post the question as written for the test. I think it would help us all to understand the answer of 1.5 stops difference better.

    Now I've decided from this thread that my interpretation of a three to one ratio being a 1 stop difference between main and fill is wrong (According to the book). But I have yet to see anyone come up with a comprehensive and clear cut explaination of a 3:1 ratio on this thread. How sad. We are CPPs Masters and Veterans of years of experience and something as basic as Ratios still draws conflicting conclusions. This is a testimony to the way we as an industry have allowed the basics to slip away from us. In a world of "If it feels good do it" photography the fundamental skills are being forgotten.

    Thank you Deb for the wake up call and thank you everyone who contributed to this thread. You've all given me alot to chew on.


    Where did I put that pointed hat??????

  3. #23
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    Quote Originally Posted by David A. Lottes
    Where did I put that pointed hat??????
    Well don't sit down til you find it. Ouch!

  4. #24
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    oK

    The Ratio 0f 1:3 or 3:1 are the half ratios

    a 6:1 ratio would then give 3 stops
    again it is because the value has doubled
    “The price of anything is the amount of life you exchange for it.” Henry David Thoreau

  5. #25
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    Quote Originally Posted by David A. Lottes
    Thanks for the diagram Kirk
    If you look at Kirk's diagram it says 3:1 ratio. The 3 expresses the value of the Main light and is to the left of the 1. Now I'm not sure about the dome thing. A human face is in a dome shape so I would think that is what you would want to use to meter it. Not a flat 2 dimensional diffuser. I would think the only time to use the flat diffuser would be for a reflective reading or an incedent reading on a flat surface. But that's another can of worms.
    David, that "3:1" in the diagram is a typo on my part. It should be "1:3" as I've learned it.

    As I was taught, it was a shadow illumination:highlight illumination ratio--not a fill light:main light ratio. That's why it comes out 1:3 instead of 1:2. If it were mere fill light:main light, it would merely be an expression of the bare difference in power--stops, watt seconds, watts, whatever. But because it's a ratio of the illumination that actually strikes the subject, it includes the additive effects of overlapping lights.

    Derek is adding a number for the accent lights, too, and although I can't recall seeing that expressed, it's certainly valid.

    Deb I would really love it if you could post the question as written for the test. I think it would help us all to understand the answer of 1.5 stops difference better.
    Yep.

    Now I've decided from this thread that my interpretation of a three to one ratio being a 1 stop difference between main and fill is wrong (According to the book). But I have yet to see anyone come up with a comprehensive and clear cut explaination of a 3:1 ratio on this thread.
    I just gave it to you. It's the ratio of the shadow illumination compared to the highlight illumination, taking into account that the highlight illumination is a combination of both the fill light and the mainlight. It is not a ratio of the power of the lights (at least not as far as getting the question right on the PPA exam is concerned).
    --Elephants can swim...
    ...and very gracefully.
    Knowing that,
    I do believe
    Anything is possible for me.

    Kirk Darling, CPP

  6. #26
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    I beleive Deb is referring to this question, from the sample test on this web site: http://certifiedphotographer.com/fil...ampleItems.pdf

    8. In a portrait illuminated with a 3:1 lighting ratio, comparisons of the highlight side of the face with the shadow side would produce a difference of how many stops? a. 0.5; b. 1.5, c. 2.5; d. 3.5.

    Correct answer according to the test sample is ...........B. 1.5 stops.

    Karen Linsley, Cr.Photog., CPP
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  7. #27

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    Bless you Karen
    I would have gotten that wrong before Deb posted this thread. I would have assumed it meant how many F stops difference do you set between your Main and your Fill. Now because 1 is not an option I might have figured out 1.5 as being the brightest highligt compared to the shadow side. As for the 1:3 - 3:1 confusion It seems however you learn it will work if you remeber the order, but it seems easier to remember the set up if you think of 1 as the fill (less) and 3 as the main (more). If I tried to think of my main as 1 and my fill as 3, I would get mixed up and think my fill needed to be brighter than my main. So for the test my answer would have been wrong. Now in the real world when I've set my Main to F8 and my Fill to F5.6 I am creating a 3:1 ratio, and yes the meter will read 8.6 or so in the brightest highlight. So I'm doing it right I just didn't know how to explain it. What can I say Thanks again everyone! Old dogs can learn new tricks
    Last edited by David_A._Lottes; 09-07-2006 at 04:30 PM.

  8. #28

    Default Beating this dead horse one last time!

    Quote Originally Posted by KirkDarling
    It's the ratio of the shadow illumination compared to the highlight illumination, taking into account that the highlight illumination is a combination of both the fill light and the mainlight.
    That's really more of a definition than an explaination

    Sorry Kirk.....Just being a Smart***

  9. #29
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    Hey David, Smart"aleck" has 5 *****. Don't want to get in trouble now.

  10. #30

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    OOOPS! Thanks Mark

    Yes Kirk
    I know Explaination is a Synonym for definition. Just being a Smart *****

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