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  1. #1
    Shinnya's Avatar
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    Backlit situation with incident meter

    Hi everyone,

    This is one of the situations that I cannot figure out how to get a measurement with an incident meter.

    Say, a subject is siting in front of a window where there is a lot of details in the interior that I want to keep, not to mention the face of the subject.

    How do I go about getting the measurement with an incident meter? Should I be able to do it without a spot meter?

    Any suggestion would be appreciated.

    Warmly,
    Tsuyoshi
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  2. #2

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    Yes, you can meter this quite easily with an incident meter. Take an incident meter reading from the low light position using with the incident dome pointed toward the camera position this will be your exposure...always base exposure on shadow values.

    Next, if you wish to determine the brightness range, take a reading with the dome pointed toward the camera position with the dome lit by the window light. By subtracting the low value EV from the high value EV and adding this to five you will have the SBR of the scene. From the SBR you can determine the film EI for that exposure (film EI is not a fixed value but rather a fluctuating value based upon the development that the film will recieve) You will also determine the development that the negative should require based upon the SBR.

    This is how I would meter this with an incident meter.
    Art is a step from what is obvious and well-known toward what is arcane and concealed.

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  3. #3
    Shinnya's Avatar
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    Donald,

    Thank you very much or your a quick repsonse. I can understand the frst part, but not quite the second part...

    How can I point with dome torward the camera while lit by the light from the window? Am I missing something?

    Thanks!

    Warmly,
    Tsuyoshi



    Quote Originally Posted by Donald Miller View Post
    Next, if you wish to determine the brightness range, take a reading with the dome pointed toward the camera position with the dome lit by the window light.
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  4. #4

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    Point the dome at the window. Pointing it towards the camera will shade the dome and give you the wrong EV. Not sure if this is what Donald meant to say.

    Did you want detail outside the window too.
    Technological society has succeeded in multiplying the opportunities for pleasure, but it has great difficulty in generating joy. Pope Paul VI

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  5. #5

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    Pointing the dome toward the camera lens will give you the proper exposure for the low values of the scene. Allowing the dome to be lit will give you the proper high value reasding...this can be accomplished by placing the dome perpendicular to camera lens axis.
    Art is a step from what is obvious and well-known toward what is arcane and concealed.

    Visit my website at http://www.donaldmillerphotography.com

  6. #6
    johnnywalker's Avatar
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    I think he means at the camera, but he said the dome is lit by the window in one case and the "shade" in the other.
    Donald, where does the five come from?
    I understand you can increase or decrease the EI of the film and change the development time to increase or decrease contrast, but the exact mechanism of doing it under the circumstances the original poster describes eludes me. Would you run through a quick example, using a generic film?
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  7. #7
    Shinnya's Avatar
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    I am just trying to understand the language here.

    So, when I try to read for the highlight value, I would place a meter such that one half of the dome is lit by the window light and the other half pointing toward the camera? Am I understanding it right?

    This means that the the direction of the dome will be perpendicular to the way camera is facing the subject is the subject is sitting straight from the camera. Is this right?

    Warmly,
    Tsuyoshi
    Last edited by Shinnya; 11-30-2006 at 11:21 AM. Click to view previous post history.
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  8. #8

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    The five comes out of the BTZS incident metering method. At least that is the only place I have seen it. I did not understand the explanation, in the btzs book or video, but it works. I see it as an "ours is not to reason why" type of scenario.

    Shinnya, I would place the meter so it is fully lit by the light coming in from the window. It seems to me that, if you place it perpendiclar, half of the dome will be in Shadow thus not giving you a true highlight EV.
    Technological society has succeeded in multiplying the opportunities for pleasure, but it has great difficulty in generating joy. Pope Paul VI

    So, I think the "greats" were true to their visions, once their visions no longer sucked. Ralph Barker 12/2004

  9. #9

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    Quote Originally Posted by Shinnya View Post
    I am just trying to understand the language here.

    So, when I try to read for the highlight value, I would place a meter such that one half of the dome is lit by the window light and the other half pointing toward the camera? Am I understanding it right?

    This means that the the direction of the dome will be perpendicular to the way camera is facing the subject is the subject is sitting straight from the camera. Is this right?

    Warmly,
    Tsuyoshi
    That is correct.

    For someone who is approaching incident metering with the methodology of spot metering, it appears that this will not work...but it will work since the incident dome gives a range of exposure typically related to the inherent luminance of an 18% gray card.

    In this example if you base exposure or development based upon facing the dome toward the scene of maximum luminance you will have an erroneously high reading...resulting in underexposure (if you base your exposure on this reading) or in development (if you base your luminance range on that reading).
    Art is a step from what is obvious and well-known toward what is arcane and concealed.

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  10. #10

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    Quote Originally Posted by johnnywalker View Post
    I think he means at the camera, but he said the dome is lit by the window in one case and the "shade" in the other.
    Donald, where does the five come from?
    I understand you can increase or decrease the EI of the film and change the development time to increase or decrease contrast, but the exact mechanism of doing it under the circumstances the original poster describes eludes me. Would you run through a quick example, using a generic film?

    A typical example using Efke PL 100 developed in Pyrocat HD could be as follows.

    The subject is backlit and taking an incident meter reading with the dome pointed toward the camera, I record a EV of 6.6.

    Taking a second reading with the dome pointed perpendicular to the axis of the camera lens, I record an EV of 8.6

    Subtracting 6.6 from 8.6 gives a value of 2 which when added to 5 gives the SBR of 7. This would be a typically normal brightness range.

    From my tests of Efke film I have found that the EI of the film at a SBR of 7 is 50. The correct exposure in this case would be F 11 1/2 at 2 Seconds...which when accounting for reciprocity characteristics would be increased to 4 seconds. The proper development time for the film based upon my equipment, procedures, and desired negative density range would be 11 minutes.

    Now had I pointed the meter toward the window light, I would have recorded a SBR of 10.4 and had I followed Mark's original recommendation I would have severely under exposed the film by giving an exposure of F 11 1/2 at 1/8 second rather than the appropriate 4 seconds at F 11 1/2.

    If I had followed Mark's second recommendation I would have under developed the film because rather than having a SBR of 7, I would have have decided on a SBR of 8.8 (10.4 minus 6.6 equals 3.8 plus 5 equals 8.8) and I would severely underdeveloped the film. I would have developed the film for 7 minutes rather than 11 minutes.

    I hope that this gives you some idea of the procedure that I use.
    Last edited by Donald Miller; 11-30-2006 at 12:17 PM. Click to view previous post history.
    Art is a step from what is obvious and well-known toward what is arcane and concealed.

    Visit my website at http://www.donaldmillerphotography.com

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