How can you create a non-uniform yellow tint on a black-and-white photo?

A likely approach is selective toning rather than a single uniform color wash. Based on the answers, this look can be made with split toning or a warm color/gradient layer, then refined with masking.

A practical method:

• Start with the black-and-white image.
• Add a warm yellow/orange or reddish-orange tint using split toning, or place a two-color gradient/color layer above it.
• Set that layer to a blending mode such as Soft Light.
• Use a mask and paint/refine it locally so the warmth is stronger on selected shadows and weaker or absent in others.

The key is that the tint does not map perfectly to all dark tones, which suggests manual masking or brushwork rather than an automatic tonal conversion alone. In short: likely a warm split-tone or gradient/color layer in Soft Light, combined with local mask painting.