Which setting determines how much light passes through a layer in Photoshop?

The setting that determines how much light passes through a layer in Photoshop is Opacity. Opacity controls the transparency of a layer, meaning it defines how much of the underlying layers are visible through the current layer. When the opacity is set to 100%, the layer is completely opaque, blocking all light from passing through, while a setting of 0% makes the layer fully transparent, allowing all light to pass through with full visibility of the underlying layers.

This feature is crucial for compositing images and effects, as it allows for adjustments that can result in various visual outcomes. For instance, reducing the opacity of an image layer can create the effect of a ghosted image or allow for a seamless blend between multiple layers.

The other options serve different functions in the application. Blend mode affects how colors on a layer blend with colors on underlying layers but does not directly control light transmission. Fill is similar to opacity but specifically controls the opacity of the layer’s content while maintaining the visibility of layer styles, such as shadows and glows. Visibility simply toggles whether a layer is visible or hidden in the document, rather than controlling the amount of light or visibility passing through a layer.