Digital Polarizer

A polarizing filter is an indispensable tool for most photographers. It helps remove reflections from most nonmetallic surfaces, increases the color saturation of foliage, darkens the blue sky for dramatic effects, and so on. I try to carry one with me anytime I go out to take photographs. The operative word here is "try" since I don't always remember to pick one from the camera bag. Luckily, digital domain gave us some tools to compensate for our forgetfulness. This is how I developed a Photoshop technique that I call Digital Polarizer since the entire effect is achieved through digital manipulation.

How it works
Digital polarizer works by mimicking the features of a real polarizer. The technique works best with photographs with blue skies or blue ocean and some unwanted reflections on water. I have successfully used it to achieve richer colors even without any part of the sky showing. The reason it works is very simple. Even though the sky may not be visible as part of the image, its reflection on most surfaces is there as a slight cast of cyan. So, by removing it we can clean other colors of this invisible haze.

I will start with an image with a large area of what was supposed to be blue ocean. Feel free to copy this image and practice in Photoshop. I photographed the swan at a nearby cove and the water was indeed a nice shade of blue.

I roughly adjusted the curves to get the swan image I wanted. I did not do any color correction in red, green, or blue channels. Now comes the fun part. When I look at this photograph, I want to see the water as blue rather than bluish gray. This tells me I need to work with the "neutrals" and the "blues.". Now is the time to add a "Selective color" adjustment layer. Either use the shortcut from the bottom of the "Layers" panel or follow the menu options "Layer/New adjustment layer/Selective color." Using the drop-down color channel selector, click on "Neutrals" and move the sliders as shown below. You may write the numbers if you wish.

Each slider here represents primaries and their opposites. Cyan-Red, Magenta-Green, Yellow-Blue sliders add to the labeled color in the positive direction and add to the implied color in the negative direction. So, -29 yellow is +29 blue and so on. After checking the numbers click on OK and look at the image if you are following the tutorial in Photoshop. It should look like the following image.

We added more blue, more cyan and more black to the neutrals. It looks better than the original but we are not done yet. Now, double click on the selective color channel and this time select "Blues" from the drop-down list. Now we will adjust the blues to the values shown below.

Adjust the values as shown and click on OK. These adjustments will add to the blues more cyan, more blue, and more black. The result will appear as follows.

Now, I have a pretty close shade of blue for the ocean but I have introduced a bluish tint to the white feathers of the swan. This can be fixed by changing the blending properties of the selective color channel. Right click on the selective color channel and select "Blending options" from the pop-up context menu. We do not want the adjustments we have made in the selective color layer apply to whites. So, we move the slider as shown below.

First move the highlight triangle to the left until you read 190. Then, while holding the Alt key (on PC) click on the left half of the triangle and move it to the left until it reads around 167. This is not an exact number. It simply provides a smooth transition of the effect between that range of brightness. The finished image will have clean whites on the swan and deep blue on the ocean part of the image. Here is mine.

Compared to the original, it is a major improvement if I may so myself.

May your oceans be of the shade of blue you want.



Other tips columns
How to use a polarizing filter
Digital Polarizer
Splitting hair for wider range

Contaflex, c1960
Zeiss, 2 1/4 x 2 3/4 folding camera, front standard with Zeiss Ikon lens.

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