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Thread: Light box

  1. #1

    Join Date
    Mar 2018
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    11

    Light box

    What is the best light box for negative and transparencies.

  2. #2

    Join Date
    Sep 1998
    Location
    Loganville , GA
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    14,409

    Re: Light box

    A properly color balanced one whose output is designed for photographic results and not something designed for other fields, like medical!

  3. #3
    Drew Wiley
    Join Date
    Sep 2008
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    SF Bay area, CA
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    18,337

    Re: Light box

    If it's too cheap to be true, it is too cheap to be true. Just Normlicht was a good brand. I made my own light boxes.

  4. #4

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    May 2015
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    SooooCal/LA USA
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    2,802

    Re: Light box

    A Macbeth is a photo lab standard, but not sure if still available. ..

    Steve K

  5. #5

    Join Date
    Mar 2018
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    11

    Re: Light box

    Thank you all.

  6. #6
    Drew Wiley
    Join Date
    Sep 2008
    Location
    SF Bay area, CA
    Posts
    18,337

    Re: Light box

    Macbeth is still in business, but has been bought out by XRite. The keyword would be "Macbeth Proof Light". Pricey, but the
    real deal.

  7. #7

    Join Date
    Mar 2018
    Posts
    11

    Re: Light box

    thank you , I found a used McBeth pl-214 on EBay

  8. #8

    Join Date
    Mar 2017
    Location
    Del City, OK
    Posts
    227

    Re: Light box

    You can also build your own. That’s what I did. I made mine our of a project box, a piece of plastic that acts as a diffuser, and lined the box with aluminum foil attached with spray glue. Then you just get some LED strips and line over that, being careful not to let them short out against the foil. I used liquid electrical tape for that. Lastly I ripped up an old DC converter and hooked it up to a switch to power the thing. I used a combination of warm and cool LED’s for better color. I basically made it for free using spare parts I had on hand. If I had to buy the parts and wanted to get really color accurate, I would probably have used a mixture of red, green, and blue LED’s, like what they use in high end scanners these days. If you wanted to get really technical with it, you could use a DSLR’s histogram to calibrate the color balance.

    I’m not saying you have to go the DIY route, but it is a fairly easy project.

  9. #9

    Join Date
    Sep 1998
    Location
    Loganville , GA
    Posts
    14,409

    Re: Light box

    Quote Originally Posted by jim10219 View Post
    You can also build your own. That’s what I did. I made mine our of a project box, a piece of plastic that acts as a diffuser, and lined the box with aluminum foil attached with spray glue. Then you just get some LED strips and line over that, being careful not to let them short out against the foil. I used liquid electrical tape for that. Lastly I ripped up an old DC converter and hooked it up to a switch to power the thing. I used a combination of warm and cool LED’s for better color. I basically made it for free using spare parts I had on hand. If I had to buy the parts and wanted to get really color accurate, I would probably have used a mixture of red, green, and blue LED’s, like what they use in high end scanners these days. If you wanted to get really technical with it, you could use a DSLR’s histogram to calibrate the color balance.

    I’m not saying you have to go the DIY route, but it is a fairly easy project.
    How,do you correct for the overly blue color of the aluminum? For photo you should be around 5500K,with a CRI,of 95,or,higher,how do you measured that?

  10. #10

    Join Date
    Mar 2017
    Location
    Del City, OK
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    227

    Re: Light box

    Quote Originally Posted by Bob Salomon View Post
    How,do you correct for the overly blue color of the aluminum? For photo you should be around 5500K,with a CRI,of 95,or,higher,how do you measured that?
    You don't worry about the blue of the aluminum. Balancing the RGB LED's takes care of that. And achieving a high CRI is easy with RGB LED's. 95 is very achievable with 99 being possible. CRI basically just measures RGB light, so by creating white light our of RGB's, you're essentially cheating the test. In fact, that's why TLCI was invented. The LED's that get a bad CRI rating aren't made from an RGB array. They're made from blue LED's that are mixed with yellow and red producing phosphors to mimic white light to our eyes. That's why the RGB method is what's used in scanners and such. True white LED's don't exist.

    If you want to get a little more technical with it, you can put each color of LED on it's own circuit leg, and control the voltage (and thus intensity) applied to each color through a set of resistors or a potentiometer. As for the color temperature, you just take a photo of the light box with your digital camera and view the histogram. With the white balance set to 5,500K on the camera, all of the peaks in the photo's histogram will line up with each other when the temperature of the lightbox output reaches 5,500K.

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