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Colour Correction using Lab Colour mode

Last month, I showed how to boost colour contrast using the Lab colour space. Now I want to stay within Lab, and look at a simple colour correction. The original image is a mix of flash and a rather warm background light, creating a mixed balance of light throughout the image as seen below.

Our first step is to change the colour space to Lab mode.

SB_ColourBalance2

Within Lab there are 3 different channels, the luminance channel and 2 colour channels. The luminance channel doesn’t interest us today as we are just going to correct the colour balance rather than contrast. Looking at this image there is a red/magenta cast in the background, that can also be seen in the skin tones of the people. As channel A controls the red/green information, we need to adjust this channel in a curves adjustment layer.

SB_ColourBalance2a

SB_ColourBalance3

Select a curves adjustment layer as shown above, then in the curves dialog box choose channel A and drag the curve towards the left.

SB_ColourBalance4

dragging the curve to the left as seen above, changes the colour balance away from red and towards green. I have concentrated on correcting the colour cast in the background but this has left the foreground looking a little green and unappetising.

Using the curves layer mask we can reverse the colour correction for the foreground only. Click on the layer mask and paint with a black brush over the plate and the food to hide the effects of the curves adjustment layer.

SB_ColourBalance6

The Original image and Final image are shown below, as you can see the plate and food are the original colour while the background is more appropriate.

More:  Skin Smoothing with Photoshop

Original

Final Image

This is just scratching the surface of the colour correction abilities of Lab mode and I recommend Dan Margulis’ book for further reading.

Please feel free to comment and ask any questions below

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About Scot Baston (31 Articles)
Scot Baston is a Commercial & Wedding Photographer that lives on the south coast of Devon, that inspires much of his work. Whether it the technical or emotive sides, Photography is a passion that continues to challenge and inspire.

4 Comments on Colour Correction using Lab Colour mode

  1. Hi Scot,

    You have left yourself a cyan cast on the plate in the final image. Colour is a very subjective thing and in my view I would have embraced the warmth of the restaurant because its pleasing to the eye and brought the plate up to its surroundings as that after all is what its reflecting.

    Just a thought.

    Cheers

    Stu

  2. Thank you Stuart,

    I’ve gone back to the original file and that cyan cast is there in the original file and not introduced with my edit above. Thank you for pointing it out though.

    Cheers

    Scot

  3. Eric Bier // July 3, 2011 at 5:18 pm //

    Martin Evening says, “…I would hope by now that having learnt about optimizing tones and colors in Camera Raw, followed by what can be achieved using Photoshop, you’ll realize that these are all the tools you’ll ever need to process a photograph all the way through to the finished print stage. My response to the Lab color argument is that it is simply adding complexity where none is needed.” Adobe Photoshop CS5 for Photographers, p. 677

  4. Thank you Eric,

    There will always be many ways to achieve a goal within Photoshop, and while I respect Martin’s opinion, I feel that Lab mode offers a control that I find hard to replicate within RGB.

    Scot

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