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Thread: Distance from bulb to printing frame

  1. #1

    Join Date
    Sep 2018
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    30

    Distance from bulb to printing frame

    I know it is here somewhere, but can't find it again.

    I am getting everything ready to make the dive into carbon, and other types of printing. I am building my exposure box. What is the distance between the lights and the printing frame.

    Necessary Info:
    Using LEDs as the light source.

    Building a drawer type vacuum frame so the distance will not be adjustable, unless I can figure out a way.

    Thanks for the help.

  2. #2

    Join Date
    Apr 2011
    Posts
    85

    Re: Distance from bulb to printing frame

    I think it depends on the spacing between your bulbs and the type and size of the bulbs. I'm using fluorescent tubes with about 1/4 inch spacing between them and I find a tube-to-print distance of 1 1/2 inches is sufficient to avoid any hot spots. You may have to do some experimenting before you finalize the build.

  3. #3

    Join Date
    Aug 2000
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    California
    Posts
    2,602

    Re: Distance from bulb to printing frame

    Quote Originally Posted by Denny View Post
    I think it depends on the spacing between your bulbs and the type and size of the bulbs. I'm using fluorescent tubes with about 1/4 inch spacing between them and I find a tube-to-print distance of 1 1/2 inches is sufficient to avoid any hot spots. You may have to do some experimenting before you finalize the build.
    Good answer Denny.

  4. #4

    Join Date
    Sep 2018
    Posts
    30

    Re: Distance from bulb to printing frame

    I can do that. Now I just have to figure out how.

  5. #5

    Join Date
    Apr 2011
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    85

    Re: Distance from bulb to printing frame

    One more thing you might consider is determining the maximum area that your light source is capable of illuminating evenly. This will determine the maximum print size without falloff at the edges, and will vary with distance from bulb to print frame. If you're handy with a spreadsheet you can do some theoretical calculations to get you in the ballpark (maybe easier to calculate if you're building with fluorescent lamps), or you might just wait and test your final setup. Here's an example of a plot from an old light box that had 6 bulbs:
    Click image for larger version. 

Name:	Capture.PNG 
Views:	6 
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ID:	183400

  6. #6

    Join Date
    Sep 2018
    Posts
    30

    Re: Distance from bulb to printing frame

    Quote Originally Posted by Denny View Post
    One more thing you might consider is determining the maximum area that your light source is capable of illuminating evenly. This will determine the maximum print size without falloff at the edges, and will vary with distance from bulb to print frame. If you're handy with a spreadsheet you can do some theoretical calculations to get you in the ballpark (maybe easier to calculate if you're building with fluorescent lamps), or you might just wait and test your final setup. Here's an example of a plot from an old light box that had 6 bulbs:
    Click image for larger version. 

Name:	Capture.PNG 
Views:	6 
Size:	10.0 KB 
ID:	183400
    You can chart this with a light meter right?

  7. #7

    Join Date
    Apr 2011
    Posts
    85

    Re: Distance from bulb to printing frame

    Maybe possible with an incident meter, I've never tried.

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