Tuesday, April 15, 2008

Still More Variations on Bright Sky Processing

In what could easily become a never-ending presentation on variations in post processing, I’ll call it quits after this one. Previously, the scenario was that only one auto-exposure shot was taken of a scene with bright sky but dark foreground. The challenge was to get the best final image from either JPEG or RAW with simple post processing. Next, let’s consider a bit more involved post processing.

Show above are comparisons of the images made with a graduated neutral density filter (Image 4) from the first posting, a Photoshop simulation of a graduated neutral density filter (Image 11) and a Photoshop blend of two “exposures” (Image 12). Images 11 and 12 were made from the same raw file – only one real exposure – but processed twice in Adobe Camera Raw (ACR).

Image 11 was made from a raw file processed first with -1/2 stop of “exposure” (for the best sky) and then again with +1 stop of exposure (for the best tree/ground); this created two image files. In Photoshop CS3, the sky exposure (-1/2) was placed as a layer on top of the ground exposure (+1). The sky layer was then blended into the ground layer by using a graduated layer mask. There are many references and tutorials on this technique. Here are some links:

Sharon Lowe
Digital Camera Magazine
Luminous Landscape

A more involved variation on these ideas is shown on the Luminous Landscape – one of my favorite photo sites. Image 12 above was made with that blending process but simplified by using Fred Miranda’s DRI Pro plugin for Photoshop. First, using ACR, two variations on exposure, + ½ stop and – ½ stop, were made from the same raw file and then saved. These two variations were loaded into DRI Pro.

Of course, you can use two or more real exposures instead of simulating exposure variations in Photoshop. Image 13, below, was made from two real exposures, +1 and -1, using DRI Pro. And then, there’s High Dynamic Range (HDR) …

High Dynamic Range is a computer based method of combining several exposures to increase the tonal range. Some like HDR and some do not; in fact, sometimes I like HDR and sometimes not. HDR images can be a bit over-the-top according to the final processing -- the “tone mapping”. There are a number of HDR software packages available. I usually use Photomatix and/or the HDR features contained in Photoshop CS3. Some of my favorite images are HDR based.

Both Image 14 and 15 above were made from three exposures at -1, 0, +1 using Photomatix. For Image 14, tone mapping was done using the default settings – a somewhat gentle and conservative approach. Image 15 was done using a more aggressive tone mapping approach.

Of the infinite possibilities, I’ve shown 13 variations on the theme of photographing and processing images for scenes having a bright sky but dark foreground. The interesting aspect of all this is that each of these methods has a place and that someone – but not everyone – will prefer one method instead of the others. But then, that’s photography and photographers!

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