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  1. #91
    Greg Davis's Avatar
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    I am thinking of something similar. I think I will indeed attach the wedge to the bottom of the glass to be in contact with the film, rather than above the glass like the original. But rather than let the glass be loose and depend on its weight for pressure, I will put thin black paper under the film to press it upwards. The glass is not heavy enough to do much, so shimming under the film is probably the best way to go with this design. I think I will have to filter the light to reduce exposure rather than increase, so I can lay the ND filters on top of the glass and keep the time to the original 1 second. Longer than that and I start getting into reciprocity failure. I could also replace the original spacer pictured above with a piece of processed film, which would make the gap smaller. The spacer serves no other purpose.
    www.gregorytdavis.com

    Did millions of people suddenly disappear? This may have an answer.

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  2. #92
    Bill Burk's Avatar
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    Or you could increase the spacer, to fit a standard piece of glass in the original channel. Get the glass chamfered so the film will slide under it. Tape the wedge underneath. I don't think you need to be critical about contact with the step wedge, not like you care about the sharpness of the image.

  3. #93
    Greg Davis's Avatar
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    Well, I just ordered a piece of .5mm thick glass as you were typing. I actually got two types: soda-lime and alkali free. I will see which is the most colorless when they get here.
    www.gregorytdavis.com

    Did millions of people suddenly disappear? This may have an answer.

    "No one knows that day or hour, not even the angels in heaven, nor the Son, but only the Father." -Matthew 24:36

  4. #94
    ic-racer's Avatar
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    Looking at that design I think it will work fine in its original configuration. There will be no bleed around the edges of the step wedge (so perfect contact is not needed). There is potential for a small amount of bleed between the steps, but I suspect it is insignificant.

  5. #95
    Greg Davis's Avatar
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    To revive this old thread... I got a piece of glass 0.5mm thick and installed everything as it was originally. The glass was very difficult to cut without shattering it, and in fact I never got a usable piece and am ordering more this week, but I got some in there to see how things work. Because of the gap between the film and wedge, there is significant bleed from one step to the other, making a clean reading with my densitometer impossible. When the new glass arrives, I am going to install the tablet under the glass, closer to the film and see how it works there. I also found the potentiometer that controls the time for the light. As I wrote earlier about this machine: there is a sensor that measures the light inside to compensate for loss thereby extending the exposure time. This potentiometer allows me to adjust the exposure time to just shy of 1/2 a second. This should eliminate problems with reciprocity. I can easily remove some of the ND layers to get a good exposure.
    www.gregorytdavis.com

    Did millions of people suddenly disappear? This may have an answer.

    "No one knows that day or hour, not even the angels in heaven, nor the Son, but only the Father." -Matthew 24:36

  6. #96
    Greg Davis's Avatar
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    As a post script, I found that I can remove a couple panels inside in order to get my color meter in there to read the illumination and color balance, and my Calumet shutter speed tester to read the exposure time.
    www.gregorytdavis.com

    Did millions of people suddenly disappear? This may have an answer.

    "No one knows that day or hour, not even the angels in heaven, nor the Son, but only the Father." -Matthew 24:36

  7. #97
    ic-racer's Avatar
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    As I wrote earlier about this machine: there is a sensor that measures the light inside
    Good to see this project coming together.

    Also, since you got your machine, I got ESECO sensitometer which also has sensors to to provide feedback on light intensity. The ESECO also firmly compresses the film right against the step wedge using a felt pad to produce sharp boundaries for the steps.
    Click image for larger version. 

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  8. #98
    Photo Engineer's Avatar
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    My old EGG died a while back and nothing I can check appears to be bad so it must be the lamp. I guess I have to spring for one somehow.

    PE

  9. #99
    ic-racer's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    My old EGG died a while back and nothing I can check appears to be bad so it must be the lamp. I guess I have to spring for one somehow.

    PE
    PE, did you ever get a new lamp? They are available, though they probably need to be soldered to the socket base of the original lamp.

    http://www.xenonflashtubes.com/strobe-spiral.html

    I probably don't need to tell you but just in case anyone out there is reading. Any time the capacitor is charged, the same voltage is always present at the lamp socket. There is no 'switch' or relay to control voltage to the lamp. And, even when the unit is turned off, there still can be voltage applied to the lamp socket for some period of time!
    Last edited by ic-racer; 01-28-2015 at 09:58 AM. Click to view previous post history.

  10. #100
    Photo Engineer's Avatar
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    I never bothered with the older unit as I have 2. I gave my 3rd away. And I know about the voltage. That is also true of old tube TV sets which can carry a lethal voltage for a day or more.

    Thanks.

    PE

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