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Mary 15
Participating Frequently
June 2, 2018
Answered

On Averge How Long Does It Take to Colour Correct an Image

  • June 2, 2018
  • 4 replies
  • 1096 views

Hello,

    I am newbie to colour correction, been working on it, on and off, for about 5 months. Please can someone tell me on average,how long will it take to colour correct a painting that has been scanned ( reproduction of a painting, aiming to closely match the original).

    Thanks for your time, your response will be highly appreciated.

D.Mary

    This topic has been closed for replies.
    Correct answer D Fosse

    Impossible to say. This is too broad a question, you need to narrow it down to specifics.

    I'd recommend photographing over scanning. A good raw file is much easier to control and correct than an RGB file out of a scanner. And with a good camera and lens you get much better resolution and sharpness - even if the original is a 35mm slide.

    First of all, you need one of these. Include this in the shot, or a reference shot done at the same time under identical conditions:

    You will never ever get a perfect colorimetric match, meaning a full match in numbers if you took measurements and compared. And even if you did, it wouldn't look right. Any measurement device will "perceive" the original pigments differently than the inks on paper, and different light sources will also influence the perceived color. Look up "metamerism" on Google.

    What you use the colorchecker for is to set the basic tone curve. All these patches, including the neutral ones, have standardized Lab values. This way you set the basic brightness and contrast - but note, it only works on flat surfaces in flat light, not for 3D objects.

    As for the colors, work visually and aim for equivalent color. It needs to be internally consistent, you can't have "runaway" colors (which is what tends to happen if you go by numbers only). If it looks right, it is right. Use the colorchecker as a visual reference if you're in doubt - not the numbers, just how it looks.

    Which brings up the next point: you absolutely must have a good monitor, calibrated to match the output conditions. This means monitor white needs to be a visual match to paper white, and monitor black needs to be a visual match to max ink for that paper. This is essential for a good result that will be accepted as "accurate". The aim is the holy grail for any monitor used in print production: what you see is what you get.

    For the final print, you also need to compensate the original contrast curve numbers - the numbers you originally set with the help of the colorchecker - for paper color and max ink. You can do this visually if you have a monitor calibrated as described above.

    4 replies

    D Fosse
    Community Expert
    D FosseCommunity Expert
    Community Expert
    June 2, 2018

    I normally have the file reproduction ready in 5 minutes. But that's "generic". If I fine-tune for a particular paper stock I might spend some more, and if extensive gamut remapping is necessary that can take quite a bit longer. With contemporary art some remapping is usually necessary for offset press.

    One good piece of advice is to always try to solve problems globally before making selections and masks to do local adjustments. When things don't look right, it's usually a global problem, not a local one, although you might first notice it in a local detail.

    The histogram is an underrated and very useful diagnostic tool. Set it to show Colors so that you can compare all three channels. Sometimes it looks wrong but you can't put your finger on it - very often the histogram tells you exactly where the problem is.

    But again - all of this is moot if you don't have a high quality monitor, appropriately calibrated for the actual output and viewing conditions. That's the very first thing you need to be concerned about.

      M
      Mary 15Author
      Participating Frequently
      June 2, 2018

      D. Fosse thanks so much for your time. The information and techniques which you have shed light on, will help me a lot. Once again thanks for your time.

         I took around 6 hours to get through colour correcting, a painting that was scanned, guess that’s way too long.

      Chuck Uebele
      Community Expert
      Chuck UebeleCommunity Expert
      Community Expert
      June 2, 2018

      6 hours is s long time! Once you get your system dialed in as Dag recommended, it should not take very long.

      Chuck Uebele
      Community Expert
      Chuck UebeleCommunity Expert
      Community Expert
      June 2, 2018

      To add to what d fosse said about scanning, I too would recommend using a camera with cross polarization lights. This will remove the reflection from canvas or surface texture.

      If you have everything set up, as d fosse suggested, you should be able to color correct under 1 or 2 minutes.

      D Fosse
      Community Expert
      D FosseCommunity Expert
      Community Expert
      June 2, 2018

      Absolutely. As it happens I made a direct comparison a while ago - and this is not even an extreme case, just what happens on "macro-level":

        D Fosse
        Community Expert
        D FosseCommunity ExpertCorrect answer
        Community Expert
        June 2, 2018

        Impossible to say. This is too broad a question, you need to narrow it down to specifics.

        I'd recommend photographing over scanning. A good raw file is much easier to control and correct than an RGB file out of a scanner. And with a good camera and lens you get much better resolution and sharpness - even if the original is a 35mm slide.

        First of all, you need one of these. Include this in the shot, or a reference shot done at the same time under identical conditions:

        You will never ever get a perfect colorimetric match, meaning a full match in numbers if you took measurements and compared. And even if you did, it wouldn't look right. Any measurement device will "perceive" the original pigments differently than the inks on paper, and different light sources will also influence the perceived color. Look up "metamerism" on Google.

        What you use the colorchecker for is to set the basic tone curve. All these patches, including the neutral ones, have standardized Lab values. This way you set the basic brightness and contrast - but note, it only works on flat surfaces in flat light, not for 3D objects.

        As for the colors, work visually and aim for equivalent color. It needs to be internally consistent, you can't have "runaway" colors (which is what tends to happen if you go by numbers only). If it looks right, it is right. Use the colorchecker as a visual reference if you're in doubt - not the numbers, just how it looks.

        Which brings up the next point: you absolutely must have a good monitor, calibrated to match the output conditions. This means monitor white needs to be a visual match to paper white, and monitor black needs to be a visual match to max ink for that paper. This is essential for a good result that will be accepted as "accurate". The aim is the holy grail for any monitor used in print production: what you see is what you get.

        For the final print, you also need to compensate the original contrast curve numbers - the numbers you originally set with the help of the colorchecker - for paper color and max ink. You can do this visually if you have a monitor calibrated as described above.

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