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  1. #51

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    Quote Originally Posted by Stephen Benskin View Post
    Actually, I think that's the one area it has the advantage over the other types. The Mark VII has two settings that appear to be practical only for short exposure reciprocity testing.


    Steve
    Not sure I understand. Does the Mark VII have some system for long exposures, say longer than one second?


    Sandy

  2. #52
    Stephen Benskin's Avatar
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    Quote Originally Posted by sanking View Post
    Not sure I understand. Does the Mark VII have some system for long exposures, say longer than one second?
    Sandy
    No, I was thinking reciprocity failure on the other end of the scale - ie short. Either way, reciprocity failure doesn't fall within the parameters of the ISO standard. But it must be nice having the ability to test for long exposure reciprocity.

    I just looked up Wejex. Sounds like a nice little device. They mention the choice of a blue or green filter. That sounds like it was designed for X-Ray film testing. Do you know the color temperature of the light source?

    Steve

  3. #53
    Bill Burk's Avatar
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    The E stands for Edgerton, who gave us stop-action studies of bullets piercing playing cards and balloons. His talent was controlling flash length. We are fortunate he could slow things down enough to give us 10-2 (1/100th-second) flash. But no, for long exposures (where I am likely to work shooting moving water in shady canyons), the EG&G won't take us there.
    Shoot.
    I wasn't worried about this until now.

  4. #54
    ic-racer's Avatar
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    Some more EG&G pictues. This is the ignition coil.

  5. #55
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    Here is the light box that sits on top of the bulb:


  6. #56
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    Here I am prepared to make the filter set. Since my clear filter that came with the unit was plexiglas, I used plexi for the other two that I made.

  7. #57
    ic-racer's Avatar
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    I used a saw to cut the plexi, then smoothed the edges with sandpaper.


  8. #58
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  9. #59
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    This shows the two filters, painted black on one side, ready to have lines scraped into the paint.



    Completed filters:
    Last edited by ic-racer; 03-27-2010 at 03:48 PM. Click to view previous post history.

  10. #60
    ic-racer's Avatar
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    Quote Originally Posted by Stephen Benskin View Post
    No, I was thinking reciprocity failure on the other end of the scale - ie short. Either way, reciprocity failure doesn't fall within the parameters of the ISO standard. But it must be nice having the ability to test for long exposure reciprocity.

    I just looked up Wejex. Sounds like a nice little device. They mention the choice of a blue or green filter. That sounds like it was designed for X-Ray film testing. Do you know the color temperature of the light source?

    Steve
    The current model blue/green Wejex is in a little different box than the older ones and the innards may be different. The older ones like mine use a white light source. Mine has a small incandescent bulb. All the electronics in side are run from 120 AC; there is no 'power supply' per say.

    The size and configuration of the box is designed for evenness of illumination. The bulb is placed some distance from the diffuser to minimize cosine effects at the edges.

    In mine there is a shutter on a stepper motor, keying off the 60hz mains and rotating about 30 rpm. It takes about 2 seconds to rotate, but the exposure through the shutter is about one second.

    Light intensity is adjusted via a hefty AC rheostat. There are two test ports for an AC voltmeter to verify the voltage on the bulb. Realize this was sold as a 'control strip' maker, not an ANSI testing device.

    Nonetheless, as long as the voltage on the bulb is checked before the run and is constant, one can make pretty good relative film speed determinations.

    Lamp Voltage Test ports on bottom. The rheostat adjustment for light intensity is under the round cover:


    Step wedge permanently mounted on the top panel under glass. I was able to take the top panel off and interrogate the wedge with my densitometer:


    Filter drawer (not pulled out far enough to see the filter) I put an 80A in there for daylight correction:

    Last edited by ic-racer; 03-27-2010 at 03:49 PM. Click to view previous post history.



 

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