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  1. #1
    indy jones is offline Member
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    Default Lighting Conditions

    Our light wall is D50 compliant. We have 2 proof one Epson Proof and one Durst proof printing on Greenlights material. When we view color the 2 proof are close in color. We take the proofs to our clients light wall, they are also D50. The problem we have is the Greenlight proof looks too yellow and the paper white looks yellow too. The Epson proof looks fine. We took temperature readings using Eye One Share the temperature is 4920 K. What would cause the Greenlights proof look yellow and the Epson proof look fine on clients wall. On our color wall it looks fine.

  2. #2
    gordo's Avatar
    gordo is offline Senior Member
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    Default

    Could be optical brightening agents in the paper (as well as varying UV content in the lights).
    Take the papers that you are using into a dark room and look at them under a flourescent black light. If they glow by different amounts then that is likely the cause of the color disconnect.

    Best, Gordo

  3. #3
    Bret Hesler is offline Senior Member
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    First guess, is optical brighteners in the Greenlight paper, and a difference in D50 lighting between you and your client. There was a recent change to the lighting spec, and Just and GTI have added UV into their formulations. Further, your Epson proofing paper is either low of free of optical brighteners.

  4. #4
    Stephen Marsh is offline Senior Member
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    Are you simulating paper tint with ink, or are you just using the native paper white point (I presume that both machines would use different inksets)? With an uncut/no UV filter spectro, measure the ink free paper white of both papers. What are the L*a*b* values of both papers (most importantly the b value, which will likely be negative and perhaps greatly more so in one paper than the other)?


    Stephen Marsh

  5. #5
    indy jones is offline Member
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    Thanks for your replies. We have switched the lights to the new standard. Our D50 lights are from GTI. They have a 3 digit code on bulbs with the last digit ending with an E, it complies with new standard. Clients and our color wall have new light bulbs to spec. I am not simulating the tint on the green lights material. The lab paper white values are as follows. Epson paper L* 96.2 a* -0.4 b* -2.3 and Greenlights L* 96.7 a* 1.2 b* -3.4. One note client GTI lights boxs have 8 bulbs in them T8 32 watts and our Gti light box have 4 bulb T12 40 watts. When you say difference, do you mean in color temperature or illumiance?

  6. #6
    Bret Hesler is offline Senior Member
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    It sounds like you have the right bulbs. I was referring to a difference in the spectral composition of the two D50 lights (Just vs. GTI or old standard vs. new Standard). We had to replace a diffuser on one of our booths after switching to the new bulbs. It was clear plexiglas, and it was blocking much of the UV from the new bulbs.


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