 If no pixels currently exist, then the 'painted' pixels are created as if in Normal blending mode.Subsequent strokes that overlap are then calculated based on the tool's blending mode, and the result is applied directly to the layer.A key difference with tool versus layer blending is that the results of tool blends are generally not able to be adjusted after the stroke is made, with the exception of stepping backward with the application's Undo command; layer blends may be adjusted with opacity or even switched, as they are applied dynamically between layers.