Step 1: First, create a new document and place the photo. You can download the one I used here or use the picture below

Resize the picture if necessary (by going to Image > Image Size and type an appropriate value)

Step 2: Press Ctrl-J to duplicate the photo. Go to Filter > Blur > Motion Blur and use these settings:

Step 3: Go to Edit > Transform > Perspective and you will see 8 dots. Try to scale them like this:

Click on the Move Tool to leave this mode. A dialog box will appear and you just click on Apply

Step 4: You are now on the Move Tool. Now tick on the Show Transform Controls checkbox on the top toolbar and rotate the current layer as you see in the image below:

It will be our light so you should enlarge it to cover all her body. Leave this mode (click on the Move Tool and choose Apply). Turn off the Show Transform Controls, we don't need it any more

Step 5: Press Ctrl-I to invert its color and change the Blending Mode of this layer to Color Dodge

Now you can see our light:

It doesn't look real so we need some more steps.

Step 6: Use the Pen Tool (P) to make a selection that includes the outer side of the light by placing some points like the picture below. Right click and choose Make Selection. The Make Selection dialog box will appear and you should use a Feather Radius of 5 pixels or more

Step 7: Use the Eraser Tool (E) with a soft brush to erase the outer side of the light. Press Ctrl-D to deselect the current selection. Repeat step 6 and 7 with the other side. Now the light looks more real!

Step 8: If the light is still too bright, you can reduce the Opacity of the current layer to have a softer light

Step 9: Press Ctrl-U to open up the Hue/Saturation dialog box and try playing with these slide bars

Well, it's all! Here is the final result:

It is a simple way to get a nice lighting effect, you can try to use other tools to make our light more attractive. Good luck!

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