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  1. #31
    benjiboy's Avatar
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    Quote Originally Posted by Galah View Post
    The dome does, actually, have a 180 degree field of view, what it doesn't have is a 360 degree field, and what would be the point of having that?
    The point would be that if the incidental light receptor could "see" around the meters body 360degrees it could evaluate the backlight as well as the frontlight at the same time, thus avoiding having to taking two readings and averaging them.
    Ben

  2. #32
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    Quote Originally Posted by benjiboy View Post
    The point would be that if the incidental light receptor could "see" around the meters body 360degrees it could evaluate the backlight as well as the frontlight at the same time, thus avoiding having to taking two readings and averaging them.
    I'm struggling to see a reason for that type of averaging.

    Can you give a practical example demonstrating the advantage?

    -----

    The reason that a normal incident meter's dome is hemispherical is to be able to meter for the light falling on a 3D subject.

    It is designed to "read" (average?) the way the "dark" & "light" parts of the side visible to the camera are lit and (thankfully) ignore back-lighting/reflected light.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Ana´s Nin

  3. #33
    benjiboy's Avatar
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    [QUOTE=markbarendt;1140029]I'm struggling to see a reason for that type of averaging.

    Can you give a practical example demonstrating the advantage?

    -----

    The reason that a normal incident meter's dome is hemispherical is to be able to meter for the light falling on a 3D subject.

    It is designed to "read" (average?) the way the "dark" & "light" parts of the side visible to the camera are lit and (thankfully) ignore back-lighting/reflected light.[/QUOTE

    It's called The Duplex Method that is described in The Exposure Manual by Dunn and Wakefield and using it no matter what direction the light is coming from even in extreme backlighting it produces correct exposure, you take one reading from the subject to the camera in the normal way and take a reading, then point the the dome at the Sun and take another one, then all you do is average the two reading,. I've been using it for many years, try it it works
    Ben

  4. #34
    markbarendt's Avatar
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    Quote Originally Posted by benjiboy View Post
    Quote Originally Posted by markbarendt View Post
    I'm struggling to see a reason for that type of averaging.

    Can you give a practical example demonstrating the advantage?

    -----

    The reason that a normal incident meter's dome is hemispherical is to be able to meter for the light falling on a 3D subject.

    It is designed to "read" (average?) the way the "dark" & "light" parts of the side visible to the camera are lit and (thankfully) ignore back-lighting/reflected light.
    It's called The Duplex Method that is described in The Exposure Manual by Dunn and Wakefield and using it no matter what direction the light is coming from even in extreme backlighting it produces correct exposure, you take one reading from the subject to the camera in the normal way and take a reading, then point the the dome at the Sun and take another one, then all you do is average the two reading,. I've been using it for many years, try it it works
    I think I see what you are suggesting; basically, by duplexing the reading you are making a decision to add more importance/consideration to the background and improve it's detail.

    That's a valid exposure decision. And yes, averaging a "normal" incident reading against a contrasting background reading, dark or light, would add available detail in the background but it also skews where the main subject falls on the film's curve.

    For me, a normal incident reading places exposure properly. The main subject always trumps the background and I'm generally happy to let the background fall where it falls.

    I only adjust the camera to "place" the background exposure when I'm using artificial light to "place" the main subject's exposure.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Ana´s Nin

  5. #35
    benjiboy's Avatar
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    Quote Originally Posted by markbarendt View Post
    I think I see what you are suggesting; basically, by duplexing the reading you are making a decision to add more importance/consideration to the background and improve it's detail.

    That's a valid exposure decision. And yes, averaging a "normal" incident reading against a contrasting background reading, dark or light, would add available detail in the background but it also skews where the main subject falls on the film's curve.

    For me, a normal incident reading places exposure properly. The main subject always trumps the background and I'm generally happy to let the background fall where it falls.

    I only adjust the camera to "place" the background exposure when I'm using artificial light to "place" the main subject's exposure.
    All I can say Mark is it works for me
    Ben

  6. #36
    markbarendt's Avatar
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    Quote Originally Posted by benjiboy View Post
    All I can say Mark is it works for me
    I'm absolutely cool with that.

    We all have differing styles and needs.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Ana´s Nin

  7. #37
    2F/2F's Avatar
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    Quote Originally Posted by benjiboy View Post
    The dome can't "see 180 degrees" 2F/2F because it can't see behind the meter body, there were however in the late 1950s a proposed version of Western Master meters with two hemispherical receptor domes one facing forward, and one back to take 180 degree light into consideration in one reading that was never manufactured, but this Duplex method can be achieved by taking two readings one in each direction and averaging them .
    Hi,

    I don't understand this statement. The dome does indeed gather light from a 180 degree area. How to most effectively place those 180 degrees of coverage in different situations is the topic of the thread.

    Also, the quotaton you used was not written by me. I said:

    Quote Originally Posted by 2F/2F View Post
    The dome, covering 180 degrees, takes that flare/spill into consideration. This is why I prefer it to the disc for measuring lighting ratios.
    As for your second post, in which you used "360" instead of "180" – Was the first "180," that I quoted above, a slip, when you meant to write "360?" – averaging a main light and a back light gives you an underexposed main subject and an overexposed background. Each ends up under-or-over exposed by half the difference between them. It is in somewhat the same way that taking a down-the-middle-toward-the-camera reading in ratio lighting results in overexposure of the film by half the difference between the two readings.

    If you want to bring the background down in tone without burning/dodging, and you have control of your light, you just need to add more light to the part of the main subject that is visible in the picture. That way you can bring down the background without underexposing the main subject.

    In a backlit situation in which I might want to bring down the background, but I am working with uncontrolled light, I still expose for the subject and burn the background when printing rather than underexposing the main subject in order to make the background print better. Either way you have to burn or dodge, but digging good tonality and detail from an underexposed main subject is much less likely to succeed than digging good tonality and detail from an overexposed background.

    But you are obviously set on your method, so I will just say as a tip that to do that, you don't even need to take two readings. Just place the dome parallel to the imaginary plane that runs between the main light and the back light and you have a one-step directly-readable average of the two lights.
    Last edited by 2F/2F; 02-17-2011 at 10:37 PM. Click to view previous post history.
    2F/2F

    "Truth and love are my law and worship. Form and conscience are my manifestation and guide. Nature and peace are my shelter and companions. Order is my attitude. Beauty and perfection are my attack."

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  8. #38
    benjiboy's Avatar
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    The book I quoted The Exposure Manual by Dunn and Wakefield shows a series of pictures on Kodachrome of the authors wife taken outdoors in sunlight at hourly intervals throughout the day using this Duplex Method, and every one is correctly exposed, I've used this method ever since I first read the book about a quarter of a century ago with various light meters, and all I can say is it works for me.
    Last edited by benjiboy; 02-19-2011 at 09:07 AM. Click to view previous post history.
    Ben

  9. #39
    markbarendt's Avatar
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    I want to say again that I have no problem with your use of that technique, nor do I doubt your success in using it.

    That averaging method is essentially a way of applying "weighting" principles to an exposure decision, much like an automated matrix meter tries to do.

    But, for your statement to be true
    Quote Originally Posted by benjiboy View Post
    every one is correctly exposed
    one needs to make the assumption that there is one "correct" exposure for any given shot.

    One correct exposure setting for a given shot has never been the case for photography as a discipline.

    Exposure placement is an artistic or technical endeavor to get a locally defined result.

    You and I will almost always place our exposures in different spots, no foul here either way, you and I just "weight" what's important differently.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Ana´s Nin

  10. #40
    2F/2F's Avatar
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    If making the background darker at the expense of making everything in the shot darker is important to you, then that is one way to do it. But to simply say that it is the correct exposure is not quite right. It is only the correct exposure if you have decided that having two different parts of the picture incorrectly exposed equals having the whole picture correctly exposed. You end up with a background that is overexposed, and also end up with a main subject that is underexposed. Exactly the problem with averaging and with in-camera meters, exactly what you are trying to get away from by using an incident meter, and exactly why it is such a bad idea in most cases.

    It would be much better to simply shoot in different light. Why put someone in the shade up against a bright background with no fill light if you do not want the background to be bright in the photograph? Why are you shooting a person if you are not exposing for them, unless your aim is specifically to not show what the person looks like (perfectly fine, but not standard)? It's at best an artistic decision that results in a darker-than-normal subject, and at worst a sloppy compromise to work around inattention to lighting.

    I am sure you get printable results, especially in situations in which the background is not that much brighter...but not ideal results.

    And I am still wondering about the statement that the dome does not take in light from a 180 degree field.
    Last edited by 2F/2F; 02-19-2011 at 05:24 PM. Click to view previous post history.
    2F/2F

    "Truth and love are my law and worship. Form and conscience are my manifestation and guide. Nature and peace are my shelter and companions. Order is my attitude. Beauty and perfection are my attack."

    - Rob Tyner (1944 - 1991)

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