Simple Exposure Blending

More often than not – and more often than we appreciate – we run out of contrast latitude or dynamic range, especially with smaller digital sensors. To help the issue doesn’t always warrant a full blown HDR and/or Tonal Mapping exercise, for which we would want 2-3 properly over- and under-exposed images anyway.

I would like to show you a simple technique, which has become one of my favorites and most used Photoshop actions over the past years. In fact, I have been using this for so long, I cannot recall where or from who I learned about it – very likely that it was Mark Galer. If not, thank you mystery contributor, I will credit you as soon as my Altzheimer Lite subsides.

Before I start, this cannot be done with a JPEG, as non-existing information cannot be retrieved.

What you see here is the point of departure, clearly out of dynamic range. The clouds and some of the highlights of the rocks at the bottom are blown and without detail, whilst some some of the rock crevices appear as just black holes.

Assuming that you do not have 2-3 over-under-exposed images, but at least a RAW file, develop one underexposed to the extend where your blown highlights start showing detail and another one overexposed to the extend where the shadows start showing details. Always use the histogram as a reference, your screen is not good enough, neither are your eyes – trust me.

Open both images in Photoshop and paste the darker version onto the lighter one, which should look something like this:

Please bear with me here: Click on the bottom layer and select all (ctrl+a), then copy that selection to your clipboard (ctrl+c). Click on the top layer and create a layer mask for that top layer. Alt+click on that layer mask which will turn the entire image white (don’t panic) and paste the copied layer from your clipboard into that mask(ctrl+v) … you should now be looking at something like this – no worries, you did not just convert your image to black and white:

The image looks black and white, because you pasted into a mask. Masks cannot contain colour.

With the mask still selected and looking at the “black and white image”, go to Filter>Blur>Gaussian Blur and select a value of about 10 to blur the mask. Depending on your image and its details, you may want to try different values, where high values may produce halos and low values may cause unnaturally sharp edges.

Now, simply select the bottom layer and you are done … yup, that’s it – easy, isn’t it?

From here you can do your normal image editing process, starting of with a much better image, balanced tonality and a healthy histogram.

So what just happened? In essence we created a luminosity mask by using the actual image, hiding and/or revealing wanted and unwanted areas respectively. How? Masks hide areas which are black, reveal areas which are white and partially reveal/hide areas more or less depending on the shade of gray. The darker areas of the top layer are hidden, or tuned down, by its very own dark areas created in the mask – thus revealing the lighter shadow areas of the bottom layer. Same goes for the highlights, where in turn more of the top layer is revealed, thus hiding the blown highlights of the bottom layer and showing the details of the top layer.

Feel free to comment, ask, critique, but mainly, enjoy … until next time …

All the best

Tommy

Tags: contrast latitude, dynamic range, exposure blending, HDR, histogram, JPEG, layer mask, RAW, tonal mapping

Category: Digital Imaging