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emigris
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I need to colour correct copies of nearly three hundred paintings.

Jan 30, 2013 2:00 AM

Tags: #problem #raw #canon #lightroom3

I took great care to find colour corrected daylight lamps, but, they are of the fluorescent kind, similar to the eco lamps that are now commonplace. Because they do not have a continuous spectrum (that tugsten would have) they have given all the paintins an unwanted colour cast. Can I correct one in Lightroom and save the corrections and apply them to the remaining images? If so is there a recommended way of doing it.

 
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  • Currently Being Moderated
    Jan 30, 2013 3:01 AM   in reply to emigris

    Yes, use Sync Settings at bottom of right library panel.

     

    Bob frost

     
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  • Currently Being Moderated
    Jan 30, 2013 4:20 AM   in reply to emigris

    Sync will give you the scope to change the white balance but given that the problem is 'holes' in the spectrum the white balance cannot really be adjusted to correct.  Some colours will never be rendered correctly.  

     
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  • Currently Being Moderated
    Jan 30, 2013 4:47 AM   in reply to emigris

    To do this right you should rephotograph the paintings under a full spectrum light source. You can get full spectrum, daylight balanced flourescents (I use these for painting), and then it’s a cinch to do white balance adjustments should you need to, particularly if you sample a neutral gray area (such as a WhiBal card under the same light).

     
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  • Currently Being Moderated
    Jan 30, 2013 5:58 AM   in reply to emigris

    All tungsten bulbs are full spectrum. Their problem is simply that they tend to be very orange and so require a white balance adjustment, but that's easy to do in Lightroom. My favorite incandenscent/tungsten bulbs are by SoLux, and my favorite fluorescents are by Full Spectrum Solutions.

     

    But you can get some of the best results by photographing the paintings outdoors in natural sunlight — particularly on an overcast day — since there's a lot of bright, diffuse light, and you don't have a problem with bright spots as you do using bulb sources. What I do is bring my paintings outside and set them up beneath an overhang so the light isn't too direct, and place a sheet of black velvet under them to prevent the ground from reflecting light back up onto them.

     
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  • Currently Being Moderated
    Jan 30, 2013 7:39 AM   in reply to emigris

    Do you still have the bulbs?

    If so rent or buy a passport colorchecker and shoot a frame under the same conditions.

    Import the passport color checker frame and create a color profile.

    Folow the instructions that came with it.

    Apply the profile to the paintings and hopefully this will be "acceptable"

    This should help you get closer to "fixing" the "holes" in the color spectrum.

    It wont be perfect but you should be closer.

     

    FYI you should use a passport colorchecker anyway.

     
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  • Currently Being Moderated
    Jan 30, 2013 9:41 AM   in reply to emigris

    The passport alows you to make profiles of your camera's sensor and lighting spectral response.

    So you could profile a canon and a nikon and have them both show the same colors and response, after aplying the profiles.

    At least thats what the Passport people say.

    I have noticed a difference when using the profiles, mostly in the blue/green areas but also slight red shift.

     
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  • Currently Being Moderated
    Jan 30, 2013 10:08 AM   in reply to emigris

    The color checker passport is cheap held up against a week's work. Don't trust the older ones, they fade over time. IIRC even the passport is only guaranteed for a couple of years of "normal" use (whatever that is).

     

    I've shot artwork for publication under fluorescent tube light - pretty hopeless without a color checker, but with a good profile - perhaps coupled with a preset - it works well.

     
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  • Andrew Rodney
    1,387 posts
    Apr 16, 2009
    Currently Being Moderated
    Jan 30, 2013 11:00 AM   in reply to Mark Alan Thomas

    There really isn't any true full spectrum Fluorescent despite the claims. There are two significant spectral spikes in all Fluorescent due to the nastly mercury. Solux is the best man made full spectrum light.

     

    Figure 1 in this article shows actual measurements of a Fluorescent and it isn't pretty:

     

    http://www.ppmag.com/reviews/200604_rodneycm.pdf

     
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  • Currently Being Moderated
    Jan 30, 2013 4:46 PM   in reply to emigris

    Here's an interesting article on the need for polarization in art photography:

     

    http://www.betterlight.com/downloads/conference10_speakers/guyer_Polar ization.pdf

     

    I've found cross-polarization (i.e. polarizing filter on lights AND lens) is very useful for both art and photo copying, but as explained above sometimes you need to dial it back to reveal textures. In the final analysis natural difuse light and a longer focal length lens is pretty hard to beat!

     
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  • Currently Being Moderated
    Jan 30, 2013 10:25 PM   in reply to Andrew Rodney

    The Full Spectrum Solutions BlueMax fluorescents (I use a pair of their 70 watt floor lamps) work really well in the real world due to their six phosphor mix and low mercury (70% less mercury than traditional fluorescents), and produce a huge amount of diffuse light with an effective CRI of 96 (and no UV), which makes them perfect for my studio. They work beautifully.

     

    I love the SoLux lamps, but they don't put out anywhere near as much light, they create hot spots, and they're too hot to work under. Great for more modest uses, though, and probably brilliant for displaying finished artwork.

     
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