Long Exposure Post Processing – Creating a Smooth Water Surface – Marble Slate Effect.

In this tutorial I would like to explain a basic principle in Daytime Long Exposure Post Processing.  It is a trick us photographers use to create an effect in which I call ‘The Marble Slate Effect’.  The illusion in which the water in a long exposure image looks white, clear and smooth resembling a marble slate leaving no evidence if ripples, currents or any imperfections in the water.

This is an image I recently took of which I superimposed a boat from a still shot into a long exposure image of the water.   To create this effect naturally is very hard and requires quite a long exposure with overexposing the sky.  When I took this shot I had a limited window of a clear grey sky to get my shot before the rain would start. The conditions were perfect since I didn’t want clouds in the sky, my vision was to create an image just as I did in this one: a boat sailing on smooth waters into the sea – no drama, just a calm, serene and confidant shot. But it did look like it rain any minute so after I took one shot it did actually start raining and here in Vancouver BC once it starts raining, it doesn’t really stop!


I wont go thru in this tutorial the complete steps in producing this image, but only explain what I did to the water.


This is the original image; a 6 minute exposure after I carefully separated the boat from a still shot and superimposed it in the long exposure shot:

You can see that although the water came out quite smooth, there is a dark horizontal line in the water right underneath the boat.  I opted for not doing any healing or cloning in Photoshop to get rid of it since I personally feel that the less cloning or cosmetic touching up I have to do the better and the Gradient Adjustment layer did a perfect job in eliminating it.


This is the image after it was converted to black and white with Seilver Efex Pro 2:

You can see that although the water is smooth it could still use some work.

  1. So what I did was select with the Marquee tool a rectangle shape that started from the horizon line down to the bottom of the image.
  2. I made sure to have ‘white’ as your foreground:

3. Then while the area I wanted was selected I created a Gradient Adjustment Layer and Walla:

You can see here that the dark line in the water has completely disappeared after adding the Gradient.

After some more tweaking with curves and levels the final image looks like this: