The HDR Sky

Sometimes, when you create what you thought would be a great HDR landscape, the sky, with its clouds, appears very contrasty, dirty, and ugly. The tone mapping process using a local operator such as the Detail Enhancer in Photomatix Pro, can sometime exaggerate the realism that is needed.

Global operators use advanced algorithms that look at a pixel and compare it an area of surrounding pixels. Pixels surrounded by brightness are compressed differently than those surrounded by darkness. This can cause halos, especially where the bright sky meets a much darker part of the landscape. It can also cause clouds to sometimes look unnatural.

Global operators, like Photomatix’s Tone Compressor or FDR Tools’s Simplex and Receptoruse simple algorithms that apply the same compression to the entire image. This creates a smoother, and usually less impactful image. But sometimes this smoothness is required, at least in part of the image.

In this image, the original HDR sky, made from the Detail Enhancer operator in Photomatix, didn’t look bad. But the version made with the Tone Compressor looked better. It had better color, and was smoother. The clouds looked softer, and more pastel. Here are the two versions, first the Detail Enhancer version, followed by the Tone Compressor version:

Although the sky looks beautiful, the rest of the Tone Compressor version looked very underexposed. The foreground is in total blackness, and since I was shooting an autumn scene in the Blue Ridge Mountains, I didn’t want to go that route for that part of the image.

The first inclination I had was to make a mask and insert the sky version I wanted on top of the foreground version I wanted. But the values were so different that it looked terrible. Just so you believe me, take a look:

So what to do when faced with a situation like this is to load one image in Photoshop as a layer on top of the other image. Then add a layer mask, and create a black to white (or white to black) gradient, depending on what you are trying to gradually reveal or gradually conceal. Here is how I did it:

That left me with only needing to make a Levels adjustment in the Lab Color mode to fine tune the contrast and hue/saturation.

Here is the final version:

Let me know if you like how it came out.