Polarising filters are a popular way to enhance images on-camera by increasing contrast and exposure times, as well as picking out details beneath or behind reflective surfaces. Whilst we cannot replicate the pulling of detail from behind reflective surfaces (as this uses optical effects at time of picture taking) we can simulate the colour boost and increased sky/cloud contrast given to skies when using a polariser. This contrast between white cloud and blue sky can be increased to accentuate an unusual cloud formation, the outline of a building or simply to add vibrancy to an image. Most landscape photographers will use polarising filters in this way, and while it can be over done at times it is a great way to improve your images.
Using grads again we can create effects that are similar to those achieved using polarising filters to darken skies or give them added intensity.
In the example above, we have taken a shot of the Kibble Palace in Glasgow, where a striking cloud formation was over the main spire of the glasshouses. It has the classic vibrant blue summer sky and brightly lit white cloud.
We can however add more intensity to the sky and increase the imapct of those clouds using a technique that replicates the effect of a polariser.
Select a blue swatch, or create a blue swatch with the RGBA values shown above (0, 23, 50, 100) with the image in COLOUR mode and STANDARD contrast. Use an ADD blend mode to overlay this onto the image using a GRAD gel mode.
Edit the grad to suit your composition, or to allow for a defined effect. It it's too strong, simply lighten the shade of blue, or reduce the alpha values of the image. As you can see, using this colouration adds more depth to the blues in the sky, whilst retaining the whites of the clouds.
The final image, whilst subtly different to the original has a more defined sky colour and cloud texture, and it helps bring the composition into the frame itself. You will also notice that the exposure on the building itself remains unaltered.
Next up - Using unusual colours to add impact.
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