This One's For Mr. Timbo
I've been using the tonal colouring technique lately - here's a quick guide.
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Black & white to start...
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A 'colour' layer to bring the shades closer to skin tones.
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'Multiply' and 'colour' layers to block in skin tones.
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A 'normal' layer to add more detail plus 'overlay' and 'colour' layers for mottling and hilights.
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More 'normal' and 'overlay' layers to add hilights and details.