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What to try
- Hide the top layer, then show it and change its blend mode.
- Adjust top-layer opacity and swap the two shapes while watching the sampled overlap.
What to look for: The displayed RGB value comes from the actual composed pixel. Layer order changes which color becomes the backdrop; visibility lets you inspect it directly.
How it works
Normal compositing places a source over a backdrop according to alpha. Over an opaque backdrop the result is source × opacity + backdrop × (1 − opacity). With partially transparent layers, both color and coverage must be combined; multiplying color by alpha during intermediate calculations avoids colored fringes.
Blend modes change the color-combination rule before compositing. Multiply darkens by multiplying normalized channel values. Screen uses 1 − (1 − source) × (1 − backdrop), usually brightening. Difference shows channel differences. These rules are applied per channel and still interact with opacity.
Use it in the Lab
Keep generated texture, drawing and color treatments on separate layers. In the Lab, visibility is reversible, Lock prevents edits, and Flatten visible bakes the visible blend stack into one layer.
Limits & distinctions
A blend mode is not a printer simulation. The Lab’s canvas output is a browser raster composition; printer inks, profiles and substrates can produce a different appearance.
Sources & references
Guide updated