Merging adjustment layers

You can merge an adjustment or fill layer in several ways: with the layer below it, with the layers in its own group of layers, with the layers it's linked to, and with all other visible layers. You cannot, however, use an adjustment layer or fill layer as the base or target layer for a merge.

When you merge an adjustment layer or fill layer with the layer below it, the adjustments are rasterized and permanently applied to the merged layer. Adjustment no longer affects other layers below the merged adjustment layer. (See Merging layers.) You can also rasterize a fill layer without merging it. (See Simplifying layers.)

Adjustment layers and fill layers whose masks (the layer's rightmost thumbnail in the Layers palette) contain only white values do not add significantly to the file size, so you needn't merge these adjustment layers to conserve file space.