Creating a collage with smooth fade effect

Start by opening an image of a cyclist.

Insert another image of another cyclist.

Click add vector mask button from the bottom of the layer palette.
Select gradient tool. Pick black to white gradient from the top bar. Click and drag from right edge towards left side. this will create a smooth fade effect between both images.
Insert another image.
Click add vector mask button from the bottom of the layer palette. Create a black to white to black gradient.
Apply the gradient from right edge to left edge covering the whole image.
Change the layer mode to linear light.

Duplicate the layer and change the layer mode to screen.
Select and merge all the layers. Duplicate the layer and change the layer mode to hard light.