How was non-uniform yellowish cast created on BW photos of Charles Lucima?

Question

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How was created following non-uniform yelowish cast on BW photo (author is Charles LUCIMA) ?

Image here - not safe for work.

At first, after looking at a/b channels in LAB color (see here), I though it's solid color layer with layer mark where darker areas are more yellow than bright ones. But after I tried it's not the case.

Any thoughts?

Asked by ruslan

Answer

After number of experiment it seems like it was two-color gradient applied on separate layer via "Soft Light" mode.

Answered by ruslan

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