Photography Experiment #2: HDR From One RAW File

Expanding on my last experiment with exposure bracketing whereby a photo is composed of several separate exposures using layer masks in post-processing, I found a good candidate for a similar technique where the different exposures come from the same RAW file.

Taking photos in RAW mode with a DSLR gives greater scope for post processing because you can get up to 2 or 3 or more EV out of a single RAW file.

Yesterday I took the family to Point Nepean at the very tip of the Mornington Peninsula, south of Melbourne. A beautiful spot with lots of Australian defence history. (Those of you who have read the final chapters of my novel-in-progress, Rochelle’s Briefcase, will realise I have an agenda. I’ve never been there before but needed to become familiar with the place!) I took a shot of an interesting cloud over Point Lonsdale but later thought apart from its shape the overall colour was a little bland. Blue ocean and sky, white-ish cloud. I needed to bring out some detail in the cloud.


The two exposures I extracted from the single RAW file of the photo.

Back at home I opened the RAW file in GIMP using the UFRaw plug-in and began playing with the exposure. As you can see in the double photo to the left here, the recommended exposure (bottom) contained a nicely blue-tinted ocean but the clouds were too friendly. I found that by lowering the lower exposure (top), the darker, stormy detail of the could was emphasised, but the nearby shore was too brown and dirty.

I opened the normal exposure first and used that as the bottom layer of my image.

I then reopened the same RAW file as a layer which invoked UFRaw, where I reduced the exposure to bring out the cloud’s detail. I used this as the upper layer in my image.

The next step was to apply a layer mask but unlike in the last experiment, I simply used an opaque mask to begin with. I wanted to make the top layer transparent from roughly the horizon down so the bluer ocean in the lower layer would show through. To simply make the sea transparent and the sky opaque would result in a weird transition at the horizon so I needed to make this more gradual.


Final merged version of the photo. Click the pic to see the full resolution photo at Flickr.

Using the gradient tool while editing the layer mask, and drawing with a black background and white ink, I drew a linear gradient from roughly halfway between the rock and the horizon, vertically to a point equidistant above the horizon. Here’s the final product:


London Bridge rock formation at the mercy of approaching storm clouds. Click the pic to see the full resolution photo at Flickr.

Here’ another example where I used the same technique to highlight the nearby London Bridge rock formation in the foreground while bringing out the darkness of the clouds. I think this one still has a problem with the slightly bright band above the horizon.

Again I wonder if this is true HDR. One could argue that it is because I’m taking two different exposures and combining the desired elements of each. regardless, I’m finding that layer masking is a very useful tool during post processing and if it can help improve the end result, then I’m going with it.


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