Swap a washed-out sky in minutes and keep believable light on the horizon. When a composite needs to respect highlights and shadows without tedious masking, “Blend If” gives you control over where a layer appears based on tone values.
Coming to you from Phlearn, this practical video walks you through “Blend If” inside Layer Style and shows how splitting the sliders with Alt or Option feathers a transition instead of snapping it on or off. You start on a simple black-to-white gradient to see what the Current Layer sliders do as you hide darks or lights on that layer. Then you switch to the Underlying Layer sliders to reveal your active layer only where the base image is bright or dark, which is where the magic happens on real images. Nace separates each handle to create a soft handoff so edges do not look cut out, and you see exactly where feathering pays off on ground textures and bright sky bands.
Nace moves from the demo gradient to a sky replacement with a real background, using Select Sky to build a fast mask and then unlinks the layer from its mask so the sky can be positioned independently. With “Blend If,” you hide the sky layer from the darker tones it should not cover and hide it from the lighter tones of the underlying layer where the original scene’s highlights need to glow through. The preview toggles show abrupt edges vanish as the feathered split pushes the new sky into the scene’s light structure. You watch the horizon pick up local luminance from the plate rather than a pasted look, and the sliders stay editable so you can nudge the threshold later.
The lesson goes beyond compositing into tonal color work. A Solid Color fill on Normal at lowered opacity becomes a quick grade when you use Underlying Layer to remove the tint from highlights while leaving it in the shadows. Changing blend modes like Soft Light or Color shifts the effect from luminance contrast to hue-only adjustments, and the same logic applies to Gradient Map. You build a warm highlight grade by restricting the map to brighter tones with “Blend If,” which preserves clean blacks while giving sunlit areas a controlled push. The through line is consistent: use the Underlying Layer split to target tonal ranges without painting a single mask.
You also pick up workflow habits that save time. Double-clicking the layer to reopen Layer Style keeps everything non-destructive, so you can keep experimenting after layout changes or sky swaps. Unlinking masks prevents accidental drift when you reposition the replacement layer, which keeps selections accurate without rebuilding them. Channel-specific options exist for advanced cases when you need the restriction to ride on red, green, or blue values, and you can stack both Current Layer and Underlying Layer splits to carve in two directions at once. Check out the video above for the full rundown from Nace.
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