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Thread: Reciprocity failure

  1. #1

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    Reciprocity failure

    I'm new to film. My first film camera 6 months ago is my RB67. My first LF is a Speed Graphic.

    If I wanted to shoot a long exposure lets say of a stream or something along those lines, how do I make sure I don't have reciprocity failure, short of shooting B/W.

    When I mentioned that I was thinking of shooting some longer exposed work, one photographer mentioned "reciprocity failure".

    How is that avoided, or does it really come into play for LONG exposures such as 15 minutes and so on, and even then how are those folks shooting lets say stars at night, and not getting reciprocity failure?

    Is reciprocity failure just applied to color film?

    TIA

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  3. #3

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    Re: Reciprocity failure

    One man's Mede is another man's Persian.

  4. #4
    8x10, 5x7, 4x5, et al Leigh's Avatar
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    Re: Reciprocity failure

    Check the datasheet for the film you're using. There's a broad range of characteristics.

    For example, Fuji Acros requires no correction up to 120 seconds, and only +1/2 stop up to 1000 seconds.

    Reciprocity law failure applies to all sensitized products, both color and b&w.

    The reciprocity law states that if you double the exposure time, you double the actual exposure of the sensitized material.
    When the law fails, it just means you must increase the time by more than 2x to achieve the same result.
    You still get an exposure that increases with time, but the relationship is no longer a simple multiplicative factor.
    The same failure occurs with very short exposures, like 1/10,000 of a second, but we seldom work at this end of the curve.

    - Leigh
    If you believe you can, or you believe you can't... you're right.

  5. #5

    Re: Reciprocity failure

    It really is less of a Law than it is a suggestion.


    and even then how are those folks shooting lets say stars at night, and not getting reciprocity failure?
    You don't use it at that point. You experiment until you get apertures and times that produce results you like. Then just use those. Well, I don't know about you really, or others, but that's how I do it.

  6. #6

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    Re: Reciprocity failure

    Thanks.

    A bit over my head, but I'll try to soak it all in.

  7. #7
    8x10, 5x7, 4x5, et al Leigh's Avatar
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    Re: Reciprocity failure

    Quote Originally Posted by RichardSperry View Post
    It really is less of a Law than it is a suggestion.
    Interesting comment.

    So you think the entire relationship between film speed, shutter speed, and lens aperture is merely a suggestion?

    It happens to be the entire basis for exposure calculations, i.e. the theoretical basis for photography as a science.

    - Leigh
    If you believe you can, or you believe you can't... you're right.

  8. #8
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    Quote Originally Posted by Pfiltz View Post
    I'm new to film. My first film camera 6 months ago is my RB67. My first LF is a Speed Graphic.

    If I wanted to shoot a long exposure lets say of a stream or something along those lines, how do I make sure I don't have reciprocity failure, short of shooting B/W.

    When I mentioned that I was thinking of shooting some longer exposed work, one photographer mentioned "reciprocity failure".

    How is that avoided, or does it really come into play for LONG exposures such as 15 minutes and so on, and even then how are those folks shooting lets say stars at night, and not getting reciprocity failure?

    Is reciprocity failure just applied to color film?

    TIA
    First off don't think of it as reciprocity failure, think of it as reciprocity compensation.

    Reciprocity does not just happen with color film but also happens with B&W film. In general any exposure over 1 sec with film will need compensation for reciprocity. However the amount of compensation varied for each type of film.

    You ask how is it avoided, well simply you expose for less then 1 sec, but reciprocity is not something that you really need to avoid. Just like adjusting your exposure for different filters you just need to adjust your exposure to include the reciprocity.

    If you have an iPhone, iPod Touch or iPad there is a great app called Reciprocity Timer that lets you select your film type enter in your metered exposure, and add the filter you are using. it then calculates the actual exposure for you.
    Zak Baker
    zakbaker.photo

    "Sometimes I do get to places just when God's ready to have somebody click the shutter."
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  9. #9
    Steve Smith's Avatar
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    Re: Reciprocity failure

    Quote Originally Posted by RichardSperry View Post
    It really is less of a Law than it is a suggestion.
    Yes. The reciprocity police will not come knocking at your door if you don't follow it.


    Steve

  10. #10

    Re: Reciprocity failure

    Quote Originally Posted by Leigh View Post
    So you think the entire relationship between film speed, shutter speed, and lens aperture is merely a suggestion?
    It's a continuum. It's not a matter of at some point failure occurs. I do think it's a good enough approximation or estimatation to get usable exposures.

    It happens to be the entire basis for exposure calculations, i.e. the theoretical basis for photography as a science.

    - Leigh
    Many sciences are based on approximations and estimates. I suppose how accurate these are determines how exact a science is.

    I am sure you have printed a print with middle of the road, not extreme, reciprocal apertures and times with notably different results. Why do you think film is different?

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