The Composite With a Halo
A designer composites a model photographed against a bright white studio background onto a dark blue gradient. The model was cut out with Select Subject and refined with Select and Mask using a 2 px feather. On the dark background, a visible light fringe surrounds the hair and shoulders. The designer also placed a product shot as a Smart Object with a Layer Style drop shadow, then scaled the product down by 60% - the shadow now looks disproportionately large and soft.
1. Why is the halo visible, and what is the correct fix order?
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The fringe is light background contamination left in the semi-transparent edge pixels, made worse by a global feather that blends white into the edge. Fix order: (1) go back into Select and Mask and use Refine Edge Brush on hair, plus Decontaminate Colors with output to a new layer with layer mask; (2) reduce or remove the 2 px feather - feather softens but does not remove contamination; (3) if a halo remains, apply a Minimum filter or a slight Layer > Matting > Remove White Matte / Defringe on the masked layer. Do not fix a halo with a dark stroke - it reads as a drawn outline at high zoom.
2. The drop shadow is wrong after scaling. Why, and how do you fix it non-destructively?
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Layer Style effects are rendered in document pixels and do not scale with the layer's transform by default, so shrinking the Smart Object 60% leaves a shadow sized for the original. Fix: enable Layer > Layer Style > Scale Effects (or in newer versions use the Scale Effects command after transform) to bring the shadow in proportion, or set the Smart Object's transform and then re-scale the style. Cleanest: keep the shadow as a separate layer or a Smart Object so it can be transformed independently. Verify by toggling the effect and checking the shadow's offset and blur against the new object size.
3. The product's colors look flat against the blue. What compositing step improves integration?
Read the worked answer
Match the light direction and color temperature: add a clipped Color Balance or Curves layer to the product to shift it toward the scene's cool cast, and a subtle shadow layer beneath it that follows the gradient's light direction. A light wrap (a blurred copy of the background masked to the product's edge, low opacity) integrates edges. Do this on clipped or masked layers so the Smart Object source stays editable.