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Thread: Using electronic flash with LF cameras

  1. #1

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    Using electronic flash with LF cameras

    The distance between the lens front and film plane can be noticeably greater with LF cameras than with 35mm cameras.
    Therefore is it necessary to take into account this extra distance when using a standard electronic flash on a LF camera?

    To clarify, with 35mm the flash's GN = aperture x distance; where distance can be direct or bounced.
    Therefore, with LF does the GN = aperture x (flash to object distance (bounced or direct] + distance from lens front to film plane)????

    Or conversely is there a correction factor for the light loss due to increased optical path in LF versus 35mm camera????

    regards

    Tony

  2. #2

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    Re: Using eletronic flash with LF cameras

    No it doesn't and there isn't.

  3. #3
    Charles S
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    Re: Using eletronic flash with LF cameras

    Look up bellows factor for this topic. The light source doesn't matter

  4. #4

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    Re: Using eletronic flash with LF cameras

    Do the arithmetic... in many cases any “additional distance” between the lens and film planes will be rather insignificant (in practical terms) in the GN formula.

    What is your photographic scenario... normal “average “ pictures, close-up portraits, or strobe-illuminated extreme macro work?

    The metric for when bellows extension might be worth considering is deviation from “normal infinity” bellows draw, not the difference based on camera format.

  5. #5
    ic-racer's Avatar
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    Re: Using eletronic flash with LF cameras

    1) Unless there is smoke or other optically dense gas in the camera, light rays will not diminish in intensity along their path through any camera.

    2) The flash-to-subject distance equation for exposure does not have a "camera position" component in it.

  6. #6

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    Re: Using eletronic flash with LF cameras

    Quote Originally Posted by BrianShaw View Post
    Do the arithmetic... in many cases any “additional distance” between the lens and film planes will be rather insignificant (in practical terms) in the GN formula..
    Quote Originally Posted by ic-racer View Post
    Unless there is smoke or other optically dense gas in the camera, light rays will not diminish in intensity along their path through any camera..
    Agreed with both of you. But I'm trying to understand why my electronic flash guns do not expose paper negatives in my LF camera.
    The flash guns have GNs of 30 & 46 (metric @ ISO100) I've corrected those values to suit ISO6 and have checked and tripled checked lens speed, aperture, pc-cable, lens filter [not being red], distance to object, dark slide out, lens cocked etc etc but all I get is unexposed sheets irrespective of which flash gun I use.

    regards
    Tony

  7. #7
    Charles S
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    Re: Using eletronic flash with LF cameras

    Quote Originally Posted by tonyowen View Post
    Agreed with both of you. But I'm trying to understand why my electronic flash guns do not expose paper negatives in my LF camera.
    The flash guns have GNs of 30 & 46 (metric @ ISO100) I've corrected those values to suit ISO6 and have checked and tripled checked lens speed, aperture, pc-cable, lens filter [not being red], distance to object, dark slide out, lens cocked etc etc but all I get is unexposed sheets irrespective of which flash gun I use.

    regards
    Tony
    That sounds like a sync issue. Which kind of shutter do you use ?

  8. #8

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    Re: Using eletronic flash with LF cameras

    Oh... paper neg????

  9. #9

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    Re: Using eletronic flash with LF cameras

    Quote Originally Posted by tonyowen View Post
    Agreed with both of you. But I'm trying to understand why my electronic flash guns do not expose paper negatives in my LF camera.
    The flash guns have GNs of 30 & 46 (metric @ ISO100) I've corrected those values to suit ISO6 and have checked and tripled checked lens speed, aperture, pc-cable, lens filter [not being red], distance to object, dark slide out, lens cocked etc etc but all I get is unexposed sheets irrespective of which flash gun I use.

    regards
    Tony
    Plug in your flash, remove the camera’s gg. Point the flash and the camera at a wall. Look through the back and fire the shutter. You should see a full circle of bright light in the shutter when the flash fires. Do you? Then your shutter is properly synched for your flash. If you don’t make sure if your shutter has an M/X lever it is set at X and try again. If not the you need an X synch shutter or your shutter needs service!

  10. #10

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    Re: Using eletronic flash with LF cameras

    What would a typical flash to subject distance be? and at what f stop would you shoot please?
    Bill
    "There are a great many things I am in doubt about at the moment, and I should consider myself favoured if you would kindly enlighten me. Signed, Doubtful, off to Canada." (BJP 1914).

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