I recently watched a great tip from Matt K. in which he used Photoshop and the Radial Blur filter to create long exposure like clouds. The effect was so beautifully convincing and easy to do I thought it was definitely worthwhile to create a short tutorial to add this technique to all our repertoires.
Here’s my starting image:
Press W to get your quick select tool and quickly select the sky. Don’t worry about the horizon to much, we’ll be masking it in later on.
Feather (Select>Modify>Feather or Shift + F6)the edges of your selection by 2-4px.
Step 3 :
Put your selection on a new layer by press Ctrl+J.
Add a Radial Blur (Filter>Blur>Radial Blur) to the new layer with an amount around 10 (adjust this higher to increase the effect and lower to diminish it). While still in the Radial Blur dialogue box use the horrible little preview in the dialogue to position where in your image you want the selection to appear to blur to, then click the zoom button.
Now, add a layer mask to this layer by clicking the layer mask icon. It usually resides in the bottom right of the screen and looks like a little circle in a rectangular box. With a very soft large brush set at 50% opacity paint one swipe along the horizon. This should help blend the sky and the ground. Finally, raise the opacity to 100% and with an appropriately sized brush paint back in any details that you don’t want blurred. In my case a roughly painted back in the tree on the left and a bit of the hill on the right.
Here’s my before and after:[beforeafter][/beforeafter]